Wu, K., Zhang, Q. & Poon, A. W. Integrated Si3N4 microresonator-based quantum light sources with high brightness using a subtractive wafer-scale platform. Opt. Express 29, 24750 (2021).

Wang, R., Li, J., Cai, L. & Li, Q. “Investigation of the electro-optic effect in high-Q 4H-SiC microresonators,”. Opt. Lett. 48, 1482–1485 (2023).

To test dexterity, we skied in the gloves all day and attempted to perform every necessary task without removing them. We also performed objective tests by doing a series of side-by-side tasks to make clear distinctions between products. These tasks included reaching into pockets for car keys, attaching lift tickets to pockets, using zippers, adjusting goggles on a helmet, lacing up winter boots, tying climbing knots with rope, and writing legibly with a pen on paper.

Kwon, O., Park, K.-K., Ra, Y.-S., Kim, Y.-S. & Kim, Y.-H. Time-bin entangled photon pairs from spontaneous parametric down-conversion pumped by a cw multi-mode diode laser. Opt. Express 21, 25492 (2013).

We estimate the on-chip power based on the power measured by an OSA considering the insertion losses of the lens-to-fiber coupling, the OSA and of the waveguide output end-facets. The measured insertion losses of the lens-to-fiber coupling and of the OSA are 3.0 dB and 2.4 dB, respectively. We then estimated the output power. The insertion loss of a test straight waveguide fabricated adjacent to the device is slightly below 12.0 dB for both the 780 nm and 1550 nm wavelengths. We neglect the waveguide propagation loss over this 1.2 mm long waveguide and adopted an average waveguide end-facet out-coupling loss as 5.8 dB as the maximum out-coupling loss, assuming the waveguide end-facet in-coupling loss is equal to or larger than the out-coupling loss, for estimating the on-chip power for both the 780 nm and 1550 nm light.

We describe the experimental setup in Supplementary Note 4. We fix the pump wavelength \({\lambda }_{p}\) at a cavity resonance at 787.7 nm and measure the SPDC with two-channel superconducting nanowire single-photon detectors (SNSPDs). The SNSPDs feature dark counts of ~100 Hz for each of the two channels. Figure 5a shows the measured single-photon flux detected by the SNSPDs with different dense wavelength-division multiplexed (DWDM) channels that span the corresponding cavity resonance wavelengths in the NIR. The estimated on-chip pump power is 5.8 mW, which is the maximum on-chip power obtainable from our setup using a continuous-wave semiconductor laser. We register the photon arrival times from two non-degenerate photon-pairs, namely 1569/1581 nm and 1563/1588 nm, by the time-digit converter (TDC) with a resolution of 5 ps per bin. Figure 5b, c shows the measured histograms of the relative arrival times of the two pairs of channels at a pump power of 5 mW, which feature strong coincidence. We record 60 s of data for each pair for statistics. We adopted a double-side exponential decay relation \({N}_{{si}}(t)={N}_{0}{e}^{-\left|t\right|/\tau }\) to fit the data, where \({N}_{{si}}(t)\), \({N}_{0}\) and \(\tau\) are the coincidence count in the time-bin at delay \(t\), the maximum coincidence count at zero-time delay and the photon life-time. The fitted value of \(\tau =26\pm 1{{{{{\rm{ps}}}}}}\) for both the pairs correspond to the loaded Q factor of ~\(2.5\times {10}^{4}\) in the NIR wavelengths, which is consistent with our transmission resonance measurements (see Fig. 3e). We define the coincidence counts summed up from the 12 bins within the \(\pm \tau\) range of the histograms as the total coincidence count \({N}_{{si}}\).

Sato, H., Shoji, I., Suda, J. & Kondo, T. Accurate measurements of second-order nonlinear-optical coefficients of silicon carbide. Mater. Sci. Forum 615 617, 315–318 (2009).

We input both the on-resonance near-visible pump and NIR signal waves from the drop- and input-bus waveguides, respectively (see Supplementary Note 4). In each experiment, we fix the pump wavelength \({\lambda }_{p}\) at a cavity resonance around 780 nm and then tune the signal wavelength around different cavity resonances at the blue side of \(2{\lambda }_{p}\). We fine-tune the pump and signal wavelengths around their respective cavity resonances to maximize the output DFG idler power generated at the red side of \(2{\lambda }_{p}\) (see Supplementary Note 9). We fix the estimated on-chip power of pump and signal waves at 4 mW.

IFMGA Mountain Guide Jeff Dobronyi leads our test team for this comparative review. Jeff leads skiers on powder safaris worldwide to the best resorts, sidecountry freeride runs, and backcountry ski tours. He logs over 120 days on skis each year and needs gloves that will keep his hands warm and keep water out. He goes through a few pairs of gloves each season and knows which gloves will last and which will fall apart after a few weeks. From rappelling into steep couloirs to digging snow pits and skiing deep powder day after day, Jeff's gloves take a beating.

Kuo, P. S., Bravo-Abad, J. & Solomon, G. S. Second-harmonic generation using 4-quasi-phasematching in a GaAs whispering-gallery-mode microcavity. Nat. Commun. 5, 1–7 (2014).

Photonic Device Laboratory, Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China

Dorin, B. & Ye, W. Two-mode division multiplexing in a silicon-on-insulator ring resonator. Opt. Express 22, 4547–4558 (2014).

Guo, X. et al. Parametric down-conversion photon-pair source on a nanophotonic chip. Light Sci. Appl. 6, 1–8 (2017).

We fix the pump power of the TE-mode at 1575.4 nm within the through waveguide at ~0.5 mW on-chip power (see Methods) and measure the TM-polarized SHG at the drop waveguide port. Figure 3g shows the corresponding measured SHG spectrum using an optical spectrum analyzer (OSA). The full-width at half-maximum (FWHM) of the pump and of the SHG are limited to the equipment resolution of 0.02 nm. The inset shows the top-view of the SHG scattering signal captured by a CCD camera. As the SHG is a second-order nonlinear harmonic generation driven by simultaneously absorbing two fundamental pump photons, the SHG is signified by a parabolic dependence on the pump power. Figure 3h shows the measured pump-to-SHG power dependence in a log-log scale, revealing a fitted slope of \(1.98\pm 0.01\) that is consistent with the nature of the SHG. We estimate the on-chip SHG conversion efficiency to be \({\eta }_{{SHG}}=\frac{{P}_{{SHG}}}{{P}_{p}^{2}}=17.4\pm 0.2 \% {W}^{-1}\) with the maximum waveguide end-facet out-coupling loss of 5.8 dB (See Supplementary Note 7 for details). We calculate the theoretical SHG conversion efficiency as follows37:

We fabricate the device in a cleanroom (see Methods). We characterize the waveguide transmission and SHG from a waveguide-coupled elliptical microring (see experimental details in Supplementary Note 4). The operating device has a designed waveguide of 1050 nm. Given the uncertainty of the actual \({n}_{{{{{{\rm{eff}}}}}}}\) induced by the continuously varying waveguide curvature within the elliptical cavity and the variance of the waveguide width caused by the fabrication process, we consider this device width a close match to the simulated waveguide width for MPM. Figure 3a shows the scanning electron microscopy (SEM) image of the device. Figure 3b, c shows the SEM images in zoom-in view of the sidewall and in the cross-sectional view of the waveguide end-facet, respectively. We extract a root-mean-square (RMS) of the waveguide sidewall roughness of ~7.3 nm based on analysis of the top-view SEM image (see Supplementary Note 5). This RMS is significantly larger than the previously reported value on 3C-SiC16. Figure 3d shows the near-field image measured at the through waveguide end facet by a charge-coupled device (CCD) camera upon a cavity resonance at 787.7 nm. It shows three intensity maxima, suggesting the cavity resonance has an TM20 waveguide mode while the higher-order mode in the through waveguide could be redistributed due to the waveguide tapering. The actual distribution Fig. 3e shows the corresponding lens-to-lens normalized transmission spectra of the device under a stabilized stage temperature of \(22^\circ C\). The measured transmission spectra in the 780 nm and 1550 nm wavelengths show a good double-resonance alignment for SHG between the resonances of 787.7 nm and 1575.4 nm, as indicated by the zoom-in view of Fig. 3f. The loaded Q factors of the 1575.4 nm and of the 787.7 nm resonances are around \(2.5\times {10}^{4}\) and \(1.4\times {10}^{4}\), respectively. This is lower than the \({Q}_{{loaded}} > {10}^{5}\) we previously reported11. By a Lorentzian resonance lineshape fitting, shown as the magenta dashed line in Fig. 3f, we obtain an intrinsic Q factor of ~3.0 × 104 and thereby extract a waveguide loss of ~11 dB cm−1 at 1574 nm. The free spectral range (FSR) of the 1575.4 nm and the 787.7 nm resonances are ~6.9 nm (~800 GHz spacing) and ~1.5 nm, respectively. We conduct the waveguide dispersion analysis of the resonance (see Supplementary Note 6).

Assuming \({\kappa }_{p,e}\,\approx \,{\kappa }_{p,t}/2\), we obtain from Eq. (3) the theoretical PGR efficiency of \(\frac{{PGR}}{{P}_{p}}=2.3{{{{{\rm{MHz}}}}}}{{{{{{\rm{mW}}}}}}}^{-1}\), which is close to our measured result. Our estimated PGR values are smaller than those reported values of the AlN platform38 and of the LNoI platform39. We attribute this to our un-optimized device fabrication process, as the pair-generation efficiency is primarily determined by the total cavity loss (see Eq. (3)). Figure 5g shows the CAR of the two pairs, given by \({CAR}=\frac{{N}_{{si}}}{{N}_{{{{{{\rm{noise}}}}}}}}\). Here we integrate the rare coincidence counts 1 ns away from the central peak of the coincidence counts to obtain an average coincidence count per bin and multiply the 12 number of bins adopted in the summation of \({N}_{{si}}\) to obtain the \({N}_{{{{{{\rm{noise}}}}}}}\) (see Supplementary Note 11). We obtain a high \({CAR}=3361\pm 84\) upon pumping at the on-chip power of 5 mW from the 1569/1581 nm photon-pairs. We also characterize the SPDC process using another device with a designed waveguide width of 1000 nm (see Supplementary Note 12). As indicated by the DFG process, this device generates photon-pairs in the C-band channels.

Among the warm mitts, The North Face Montana and the Black Diamond Mercury Mitts both make major sacrifices in dexterity for the warmth they provide. The nature of mitten designs is the primary cause, with one cavernous space for the fingers that simply doesn't allow the fingers to manipulate anything independently, like gloves. The lofty insulation is also quite bulky, making fine motor tasks much more challenging. Both of these mittens need to be removed for most tasks. If you need the warmth of a mitten but don't want a heated option and require some dexterity, the BD Guide Glove is almost as warm as a mitten.

Sheng, Y. B. & Zhou, L. Deterministic polarization entanglement purification using time-bin entanglement. Laser Phys. Lett. 11, 085203 (2014).

Table 2 summarizes the state-of-the-art microring-based quantum light sources from different second-order nonlinear platforms38,39. Although our PGR is limited by our Q factors, we have demonstrated a low-noise performance with the lowest \({g}_{H}^{\left(2\right)}\) among all the platforms.

For the SPDC, which is a spontaneous second-order nonlinear generation of photon pairs by down-converting one pump photon, the SPDC is signified by a linear dependence on the pump power. Figure 5d, e shows the measured power-dependence of the single-channel counts and of the photon-pair coincidence counts. We estimate the PGR inside the cavity by \({PGR}=\frac{{N}_{s}{N}_{i}}{{N}_{{si}}}\), where \({N}_{s(i)}\) are the single-channel counts from the signal (idler) flux. Figure 5f shows the estimated PGR. We observe a good linearity of the estimated PGR and obtain by linear fitting a pair generation efficiency of \(0.94\pm 0.02\) MHz mW−1 (1569–1581 nm) and \(1.32\pm 0.07\) MHz mW−1 (1562–1588 nm). We calculate the theoretical PGR assuming the triple-resonance condition as follows38:

Radulaski, M. et al. Scalable Quantum Photonics with Single Color Centers in Silicon Carbide. Nano Lett. 17, 1782–1786 (2017).

We're continually impressed with Hestra's offerings, which feature high-quality materials and excellent design and craftsmanship, model after model. Other impressive gloves are the Black Diamond Guide, Rab Khroma, and Arc'teryx Fission SV. All have burly leather exteriors and stood up to whatever our testing team tossed their way. Regarding the budget-friendly options, the Gordini GTX Storm Trooper II provides impressive longevity, and the inexpensive Black Diamond Tour was surprisingly durable, given its soft and supple leather.

Ski gloves come with a set of features that augment the glove's performance and make your day more convenient and comfortable on the ski hill. We inspected and used all of the features on each glove to get a good idea of which had a robust set of tools and which were bare-bones. We compared features such as gauntlet or cuff closures, wrist cinches, nose wipes, wrist leashes, clips, and heating elements. We also noted if the gloves came with liners.

We designed the waveguide dimensions at a thickness of 800 nm and a top width of 1000 nm, with a slab thickness of 100 nm. Figure 2c shows the numerically simulated non-degenerate DFG effective refractive indices \({n}_{{eff}}\) of the modes with wavelengths. Figure 2d shows the numerically simulated non-degenerate DFG phase-matching condition map with the non-degeneracy \(\left({f}_{s}-\frac{{f}_{p}}{2}\right)\) between the signal/idler frequencies (satisfying energy conservation) over the pump wavelength, following Fig. 2c. Here, \({f}_{s(p)}\) is the frequency of the signal (pump) light, respectively. We adopted a total accumulated phase-mismatch of \(\left|\Delta \beta L\right|=\left|({\beta }_{p}-{\beta }_{s}-{\beta }_{i})L\right| < \pi\) within the cavity as a working criterion for defining the MPM region. We notice a pumping wavelength range >10 nm and a non-degeneracy >25 THz. However, a \(\pm 50{nm}\) of the waveguide width will significantly red- or blue-shift the MPM wavelength window beyond the \(1.5 \sim 1.6\mu m\) wavelengths (see Supplementary Note 2). Finally, we adopted a bus waveguide with the same width of 1000 nm coupled to the microring cavity to input-couple the TE00 mode at NIR wavelengths while utilizing a drop waveguide with a narrower width of 400 nm to phase-match the TM00 mode in the bus waveguide and in the TM20 mode in the microring cavity. The coupling gap spacing is 200 nm for both the coupled waveguides. The interaction length is \(15\mu m\) for the through waveguide and is \(30\mu m\) for the drop waveguide. Both the waveguides are widened to a width of \(4\mu m\) for butt-coupling. Supplementary Note 3 details the device layout and the numerical simulations of the device.

A few conventional phase-matching techniques, including periodic-poling-based quasi-phase-matching (QPM)28,29, birefringence-based phase-matching30 and cyclic QPM31, are not available for the 3C-SiC material. We chose to design for a MPM, where we adopted a higher-order TM20 mode at the pump wavelength to match the effective refractive index of the fundamental TE00 mode at the signal/idler NIR wavelengths.

Jiayang Li designed, simulated, fabricated and characterized the devices. Qianni Zhang and Jiantao Wang performed the characterization of the pump-to-SHG power dependence and the data analysis of SHG. Jiayang Li, Qianni Zhang, Jiantao Wang and Andrew W. Poon wrote the manuscript. Andrew W. Poon supervised this project.

Every skier has a budget, and although we strive to test gear without regard for price, we also make a note of products that score above or below what we think is reasonable, given their price. While many of the best gloves are also the most expensive, there are a few options that provide excellent performance at a lower price than similar products. We bought several promising, affordable gloves, and the Gordini GTX Storm Trooper II impressed us the most. It covers the bases better than any model in its price range. It keeps our hands warm and dry and has displayed excellent durability. Similarly, The North Face Montana Mitts are a super warm, comfortable, and fully-featured pair of mittens that rival the performance of more expensive options at a much lower price.

Not surprisingly, adding batteries and heating elements to a pair of gloves comes at a price, and the Prevail Heated Gore-Tex gloves aren't exactly cheap. That said, they are less expensive than some other options, and we feel they perform better. While the price may be a deterrent, these gloves could be the ticket for those with chronically cold hands or who ski in especially cold environments. If you are looking for the warmest glove that doesn't require recharging, check out the Black Diamond Guide.

Lu, X., Lee, J. Y., Rogers, S. & Lin, Q. Optical Kerr nonlinearity in a high-Q silicon carbide microresonator. Opt. Express 22, 30826 (2014).

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The decision between gauntlet vs undercuff style gloves is largely a personal preference, but the cuff of your jacket is also a factor. If you prefer to keep your gloves tucked under your cuff, undercuff-style gloves can feel more comfortable and provide better dexterity. Gauntlet-style cuffs are best for folks who want to avoid any chance of snow creeping into your glove by using a cinch over the sleeve of your jacket. When deciding between the two, factor in the size of your jacket's cuffs and make a call on whether your glove could reasonably fit under your jacket cuff.

Wang, J. et al. Bright room temperature single photon source at telecom range in cubic silicon carbide. Nat. Commun. 9, 4106 (2018).

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Guidry, M. A., Lukin, D. M., Yang, K. Y., Trivedi, R. & Vučković, J. Quantum optics of soliton microcombs. Nat. Photonics 16, 52–58 (2022).

Figure 4a–f show the measured spectra using the OSA. The dashed line in each figure denotes the degenerate \(2{\lambda }_{p}\) positions. The pump cavity resonances supporting triple-resonance DFG span from 786.17 nm to 795.69 nm, giving a pump spectral window of 9.5 nm. We observe cavity-enhanced DFG from at least five different signal cavity resonances. Pumping at a cavity resonance of 795.7 nm, we observe the maximum non-degeneracy of 97 nm. Figure 4g shows in a scatter plot the measured triple-resonance-enhanced DFG modes. However, in comparison with the numerically simulated waveguide dispersion (Fig. 2d), the observed overall spectral range for attaining triple-resonance DFG is narrower. We attribute this to fabrication-induced non-uniformities. While the measured triple-resonance DFG spectral windows are wider than those reported of similar microring cavity-based work on the LNoI37 and AlN38 platforms. We also characterize another waveguide-coupled elliptical microring with a designed waveguide width of 1000 nm (see Supplementary Note 10) that shows a blue shift of the overall triple-resonance DFG spectral range, which is consistent with the numerical simulation of the waveguide dispersion (see Supplementary Note 2). Figure 4h shows the measured power-dependence of the DFG. We pump at a 787.7 nm cavity resonance and input a signal at a 1569.2 nm cavity resonance and measure the generated idler power at the corresponding 1581.8 nm cavity resonance. In the log-log scale, the idler power has fitted slopes of \(0.96\pm 0.01\) and \(0.90\pm 0.01\) dependence on the pump and on the signal, respectively, as expected from a theoretical linear dependence.

Brendel, J., Gisin, N., Tittel, W. & Zbinden, H. Pulsed Energy-Time Entangled Twin-Photon Source for Quantum Communication. Phys. Rev. Lett. 82, 2594–2597 (1999).

Bogdanov, S., Shalaginov, M. Y., Boltasseva, A. & Shalaev, V. M. Material platforms for integrated quantum photonics. Opt. Mater. Express 7, 111 (2017).

Editor's Note: This review was updated on April 27, 2024, to provide readers with advice about buying information and include additional specifications for each glove.

Xu, Y. et al. Mitigating photorefractive effect in thin-film lithium niobate microring resonators. Opt. Express 29, 5497 (2021).

It takes skilled garment designers to put all of the components together in a warm, waterproof, and durable glove without sacrificing dexterity. We were impressed by the Arc'teryx Fission SV because it combines all of the performance attributes into a comfortable and streamlined glove that is a pleasure to wear. However, you'll pay for this performance. The warmest gloves on the market have battery-powered internal heating devices, which are nice for early mornings on the slopes and during the winter's coldest days. These gloves are universally more expensive than even the most pricey unheated model.

All the data employed for this work will be made available from the authors upon reasonable request.

Fan, T., Moradinejad, H., Wu, X., Eftekhar, A. A. & Adibi, A. High-Q integrated photonic microresonators on 3C-SiC-on-insulator (SiCOI) platform. Opt. Express 26, 25814 (2018).

As consumers, we have high expectations of our gloves. Gloves and mittens create a haven for our hands and protect them from the harsh bite of winter air. We rely on our gloves to keep our sensitive fingers warm and sheltered from the elements while resort riding or touring. We don't want them to be too bulky or cumbersome, yet we don't want to sacrifice weather resistance or warmth. If the gloves can perform in all conditions and be versatile across many outdoor sport disciplines, even better.

Orais, N. M. et al. Directionally induced quasi-phase matching in homogeneous AlGaAs waveguides. Opt. Lett. 42, 4287–4290 (2017).

Table 1 summarizes the state-of-the-art resonance-enhanced SHG results from different SiC platforms13,19,20. Our SHG conversion efficiency on 3C-SiCoI is lower than the best value in 4H-SiCoI because of the limited Q factors of our platform at this stage. We characterize the same device for DFG and SPDC processes.

We first fix the pump wavelength at 780 nm and assume degenerate signal and idler wavelengths at 1560 nm. Figure 2a shows the numerically simulated electric-field amplitude distributions of a TE00 mode at 1560 nm and a TM20 mode at 780 nm, respectively, using a finite-difference eigenmode tool. To search for the potential waveguide geometry to match the effective refractive index of the two modes, we systematically vary the thickness and the width of the rib waveguide structure. Based on our previous device fabrication results, we assumed a symmetric waveguide sidewall slope of \(86^{\circ}\). We kept a thin 3C-SiC slab of 100 nm un-etched to avoid undercutting the SiO2 layer underneath the SiC waveguide. The 3C-SiC is clad by a SiO2 layer with a thickness of 500 nm. We adopted a Cauchy model with A, B coefficients of 2.553 and 0.03539 to calculate the material index of 3C-SiC. To simplify the simulation and design, we assume a straight waveguide structure. Figure 2b shows the numerically simulated effective refractive indices of the two modes with different 3C-SiC film thicknesses as a function of the waveguide width. The width corresponds to the top side of the trapezoidal waveguide cross-section. We can attain the MPM with a waveguide width of 1000 nm and a thickness of 800 nm. The MPM width increases with the 3C-SiC film thickness while the mismatch between the effective refractive indices becomes more tolerant to the waveguide width variation with a thick film.

This work is supported by the Research Grants Council of the Hong Kong Special Administrative Region, under Project 16202919. We thank Yuanbin Liu from Shanghai Jiao Tong University for helpful discussions.

Dong, N., Chen, F. & Vázquez de Aldana, J. R. Efficient second harmonic generation by birefringent phase matching in femtosecond-laser-inscribed KTP cladding waveguides. Phys. Status Solidi Rapid Res. Lett. 6, 306–308 (2012).

All of the gloves featured in this review are great products that stand above the vast majority of the market offerings. A low score in our review doesn't mean that the glove is unworthy of your attention. We had to be picky to find the best of the best. All scores are relative to the other products reviewed, and each performance metric is weighted relative to its general importance, which produces an overall score.

Chang, L. et al. Strong frequency conversion in heterogeneously integrated GaAs resonators. APL Photonics 4, 036103 (2019).

Image

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Lin, J. et al. Phase-Matched Second-Harmonic Generation in an On-Chip LiNbO3 Microresonator. Phys. Rev. Appl. 6, 1–6 (2016).

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Guidry, M. A. et al. Optical parametric oscillation in silicon carbide nanophotonics. Optica 7, 1139 (2020).

Figure 6a illustrates the principle of generating time-bin entanglement using a free-space Franson unbalanced interferometer. The photon-pairs can simultaneously travel through the short arm together and the long arm together, which are indistinguishable. The photon-pairs can also travel through the short arm and the long arm separately, which are distinguishable. When the photons re-enter the fiber system and routed to SNSPDs through the DWDM filters, the recorded histogram of their relative arrival times is shown in the Inset. We attribute the two side peaks as the distinguishable events that the two photons propagate in different arms. The central time-bin measures the photon-pair in an entangled state as \(|\psi > =\frac{1}{\sqrt{2}}({{|SS} > }_{{si}}+{e}^{i\left({\varphi }_{s}+{\varphi }_{i}\right)}{{|LL} > }_{{si}})\), where S(L) and \({\varphi }_{s}\)(\({\varphi }_{i}\)) denote the short (long) arm and the optical phase difference between the two arms of the signal (idler) photon. To separate the central peak time-bin from the side peak time-bins, we unbalance the interferometer arms by exceeding the coherence length of the photons limited by the cavity lifetime, calculated by \({L}_{c}=\tau c\), which is 7.8 mm for our case.

a Electric-field amplitude distributions of an TE00 mode at 1560 nm and of an TM20 mode at 780 nm. b Effective refractive indices of the pump mode (solid line) and of the signal/idler mode (dashed line) with different 3C-SiC film thicknesses as a function of the waveguide width. c Dispersion of the TM20 pump mode (solid line) and of the signal/idler TE00 mode (dashed line). d Calculated map of the non-degenerate difference-frequency generation (DFG) phase-matching condition.

We spent over 100 days skiing and snowboarding in these gloves with a backpack full of contenders, cycling through them all day. Testers also wore different gloves on each hand during the same runs and chairlift rides to make a true side-by-side warmth comparison. We tested palm insulation by holding ice axes and ski poles on cold ski tours.

where \({N}_{{s}_{1}{s}_{2}i}\) is the triple-coincidence counts for both the beam-split signal channels and the heralding idler channel and \({N}_{{s}_{1(2)}i}\) are the coincidence counts between the one split signal channel and the heralding idler channel. Equation (4) indicates that the noise from the idler (heralding) channel has a dominant effect. To reduce the influence, we assign one channel of the low-noise SNSPD for heralding, while using another SNSPD channel and one extra avalanche photodetector for detecting signals 1 and 2, respectively.

While these gloves are warm enough for most days at the ski resort, they can't compare to other well-insulated or heated models. They pack insulation around the fingertips, which hinders dexterity for general tasks and rules out fine motor skills, like opening small zippers or searching for items in pockets. We'd recommend a more dexterous glove for users with more refined dexterity needs, like on-snow professionals or parents. Still, for the price, these shortcomings are minor, and we recommend these gloves to anyone who needs high-performance gloves at a bargain price. If you can tolerate a little less warmth and water resistance, the Gordini AquaBloc Down Gauntlet Glove is even less expensive. And if you want more warmth at the expense of dexterity, check out the The North Face Montana Mitts.

a Illustration of the principle of generating time-bin entanglement using a free-space Franson unbalanced interferometer. Inset (i): Illustration of the three-time-bin histogram. b Measured histograms at two different piezo-voltage settings. c Measured single-channel counts with different piezo-voltage settings. d Measured coincidence counts of the central bin upon various piezo-voltage settings and fitted with a sinusoidal function.

Mariani, S. et al. Second-harmonic generation in AlGaAs microdisks in the telecom range. Opt. Lett. 39, 3062–3065 (2014).

Except for the heated gloves (more on that below), the warmest glove we tested was the Black Diamond Guide. Tester Ian Nicholson used them to summit two mountains over 20,000 ft above sea level and never changed into his mittens despite summit temperatures as low as -42F. The Gordini Storm Trooper II, Fission SV, Swany X-Change, and Outdoor Research Carbide Sensor also provide enough warmth for our testers on cold winter days at a ski resort. On the other hand, the Black Diamond Tour has little more warming capabilities than your average leather work glove, and are best used by backcountry skiers who create heat while climbing uphill. The Hestra Ergo Grip Active has no insulation at all.

We describe the experimental setup in Supplementary Note 4. By adopting the firing of the idler channel as the gating, we measure the signal channel as a heralded single-photon source. We utilize a fiber-based 50:50 beam splitter in the signal path to test the single-photon nature. The heralded second-order coherence is characterized by40:

We were impressed with the Mercury Mitt's thoughtful design, including features like a wrist cinch, nose wipe, and removable liners. We also liked the set of features found on the BD Guide. Surprisingly, the Gordini Storm Trooper II also packs a full set of features, including a nose wipe, wrist cinch, thoughtful gantlet, and clips.

a Schematics of a parametric down-conversion photon-pair source on a 3C-SiCoI platform. b Schematics of the Type-I phase-matching process. c Illustration of an elliptical microring cavity with the normalized effective nonlinearity \({\chi }_{{eff}}^{(2)}/{\chi }_{{zxy}}^{(2)}=\cos \varphi \,\sin \varphi\) as a function of rotation angle \(\varphi\) of the fields relative to the crystal x-axis. Purple represents the pump frequency, blue and red represent the generated signal and idler frequencies, respectively.

If you work in the elements, have to tend to your kids on the slopes, or just prefer more dexterity while on the mountain, finding gloves with mobility can be a high priority. Generally, thicker gloves are warmer but have less dexterity. Striking a balance between warmth and dexterity is key to finding a suitable glove on the slopes.

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Ma, C. et al. Silicon photonic entangled photon-pair and heralded single photon generation with CAR > 12,000 and g(2)(0) < 0.006. Opt. Express 25, 32995 (2017).

In some climates, like the Pacific Northwest and the Northeast, water is encountered regularly. In others, like the Rocky Mountains, dry snow is the norm. We wore each glove in wet weather in Washington and British Columbia and tested for water resistance using a 2-minute submersion test in a water bucket. The best gloves kept all liquid water out of the interior chamber and resisted soaking in the outer shell fabric. The worst performers soaked through quickly and lack an adequate waterproof membrane.

Powell, K. et al. High-Q suspended optical resonators in 3C silicon carbide obtained by thermal annealing. Opt. Express 28, 4938 (2020).

We insert the free-space interferometer into the down-stream of the SPDC experimental setup to prepare the entanglement. We pump at 787.7 nm with an estimated 5 mW on-chip power and measure the photon-pair channels of 1569/1581 nm. Figure 6b shows the measured histograms at two different piezo-voltage settings fine-tuning the interferometer long arm. The three-peak time-bins are separated by a time difference of 0.58 ns, corresponding to a path difference of 17.4 cm. The coincidence counts at the \({{|SS} > }_{{si}}\) and \({{|LS} > }_{{si}}\) time-bins are not sensitive to the piezo-voltage while the total coincidence counts in the central time-bin vary sinusoidally with the piezo-voltage. The quantum interference between the superposed photon-pair states \({{|SS} > }_{{si}}\) and \({{|LL} > }_{{si}}\) yields a sinusoidal modulation of the coincidence counts (assuming 50:50 beam splitters) as \(0.5{N}_{\max }[1+V\cos \left({\varphi }_{s}+{\varphi }_{i}\right)]\), where \({N}_{\max }\) and \(V\) are the maximum transmitted central time-bin counts and the visibility of the quantum interference. Figure 6c, d shows the measured channel counts of the signal/idler photons and the measured coincidence counts of the central time-bin, respectively. Each data point corresponds to a data collection spanning 30 s. We do not observe first-order (single-photon) quantum interference as the interferometer path difference is significantly longer than the photon cavity coherence time so the two wave-packets of the same photon simultaneously traveling in the two different interferometer arms cannot meet each other. We observe second-order quantum interference in the coincidence counts in the central time-bin. Using a sinusoidal fitting, we extract a visibility of \(V=86.0\pm 2.4 \%\). This is significantly exceeding the Bell’s inequality limit of \(70.1 \%\)23\(,\) indicating a clear time-bin entanglement. We attribute the non-ideal visibility to the drifts of the optical alignment and collimation conditions of the two interferometer arms during the experiment. We note that our Franson interferometer is not actively stabilized, and thus phase drift is potentially the main source of fringe visibility degradation. In our future work, we could employ active stabilization on the interferometer to overcome the issue. We note that the superposed \({{|SS} > }_{{si}}\) and \({{|LL} > }_{{si}}\) states do not have the same probability amplitudes in practice due to different setup insertion losses for the two interferometer arms.

Finding a pair of gloves can feel overwhelming, with so many options on the market. To help narrow down your choices, we've put together a few key buying considerations that summarize our more complete Buying Advice article.

Xue, G. T. et al. Ultrabright Multiplexed Energy-Time-Entangled Photon Generation from Lithium Niobate on Insulator Chip. Phys. Rev. Appl. 15, 1 (2021).

Finally, there are rooms for our elliptical microring to further enhance the cavity-roundtrip nonlinear interaction coefficient \(\gamma\). For example, the ellipse of a larger \(a/b\) aspect ratio can further align the cavity along the orientation that enables the maximum \({\chi }_{{eff}}^{(2)}\) (see Supplementary Note 13). However, the design tradeoff is reducing the bending radius of the high-curvature poles by the relation \({R}_{{pole}}=\frac{{b}^{2}}{a}\). To provide further elongation while avoiding a larger bending curvature, other non-circular microring configurations can also be explored, including racetracks with Euler bending49 and Bezier bending50 designs. However, special optimization of these bending structures may be required to reduce the straight-to-curve transition loss of the two different modes at the pump/signal wavelengths simultaneously. Nonlinear and quantum light sources based on the 4-bar QPM are possible due to the point-group symmetry of 3C-SiC.

Figure 1a schematically illustrates our elliptical microring resonator as a parametric down-conversion photon-pair source on an integrated 3C-SiCoI platform. We discuss our device design principles starting from classical nonlinearity based on DFG. The zinc-blende unit cell of 3C-SiC features tensor elements \({\chi }_{{zxy}}^{(2)}={\chi }_{{xyz}}^{(2)}={\chi }_{{yzx}}^{(2)} \,\approx \,34{pm}\,{V}^{-1},\)7\(.\) We adopt this theoretical value because experimental Maker-fringes measurements on bulk 3C-SiC is not available yet25,26,27. These elements mix three waves that are linearly polarized along three orthogonal crystal axes upon satisfying the energy conservation of \({\omega }_{p}={\omega }_{s}+{\omega }_{i}\), where \({\omega }_{p,s,i}\) are the angular frequencies of the pump, signal and idler. To minimize the number of waveguide eigenmodes involved in the nonlinear processes, we chose Type-I phase matching noting that 3C-SiC is non-birefringent. As shown in Fig. 1b, based on the (001) 3C-SiC film, we set the NIR input signal and the idler waves around 1550 nm to be transverse electric (TE)-polarized (parallel to the chip) with the x- and y-components of the fields, while the pump wave around 780 nm to be transverse magnetic (TM)-polarized with the z-component of the field. We must satisfy the phase-matching condition of \({\beta }_{p}={\beta }_{s}+{\beta }_{i}\), where \({\beta }_{p/s/i}\) are the propagation constants of the three waveguide modes.

Every skier and rider demands a different level of warmth from their gloves or mittens. Some people run cold and are always taking breaks to warm up their hands. Other people can ski all day wearing no more than leather work gloves. Skiers and riders in wetter climates, like the rainy Pacific Northwest or Atlantic Northeast, need gloves that will repel water and remain breathable on warmer days. In contrast, skiers in the drier, colder climates, like the Rocky Mountains, need a lot of warmth for below-zero temperatures.

Nonetheless, none of the crystalline SiC polytypes offers a large refractive index contrast with their native substrates. Photonic devices on SiC are thus often fabricated on suspended SiC films12,13,14,15 and on the SiCoI platforms11,16,17,18,19,20,21. Integrated SiCoI platforms rely on molecular bonding16,17,18,19,20,21 or anodic bonding11 to transfer the SiC films onto SiO2 substrates, which enables a better scalability for larger-scale integrated photonic circuits. The optical nonlinearity of SiC have been studied last decade13,15. Optical parametric oscillation and soliton generation are demonstrated based on high-quality-factor (high-Q) (\( > {10}^{6}\)) microresonators on a 4H-SiCoI platform17,18 while four-wave mixing is demonstrated on a suspended 3C-SiC platform with relatively lower Q factors (\(\sim 7400\))14. The demonstration of \({\chi }^{(2)}\) nonlinearity-based sources remains a challenge partly due to the difficulty to attain the phase-matching condition across an octave while engineering the waveguide dispersion. Recently, second-harmonic generation (SHG) with efficiencies of 360% W−1 and 3.91% W−1 were demonstrated in 4H-SiCoI using modal phase matching (MPM) and a suspended 4H-SiC microdisk19,20, respectively. A time-averaged efficiency of 15% W−1 using a pulsed laser was demonstrated by using a suspended 6H-SiC photonic-crystal cavity13. Moreover, Pockels-effect-based microring modulators have been demonstrated on both 4H- and 3C-SiCoI platforms21,22. To our knowledge, spontaneous parametric down conversion (SPDC)-based photon-pair sources have not been demonstrated on SiC platforms.

Kaneda, F., Suzuki, H., Shimizu, R. & Edamatsu, K. Direct generation of frequency-bin entangled photons via two-period quasi-phase-matched parametric down conversion. Opt. Express 27, 1416 (2019).

The silicon carbide (SiC) semiconductor industry is expanding rapidly driven by the growing needs for high-power electronics1. Meanwhile, integrated photonic platforms based on SiC polytypes are emerging in recent years, including hexagonal (4H-, 6H-) SiC and cubic (3C-) SiC. They offer a wide bandgap energy from 2.3 to 3.2 eV2, which enables transmissions of visible light and does not suffer from nonlinear two-photon absorption at the 1550/1310 nm telecommunications wavelengths. They also feature a high hardness for photon-phonon interactions3, a fast heat dissipation for high-speed directly modulated lasers4 and different color centers for single quantum emitters5,6. Owing to their non-centrosymmetric crystal lattices, SiC polytypes feature second-order nonlinear susceptibilities \({\chi }^{(2)}\). For example, 3C-SiC features \({\chi }_{{zxy}}^{(2)}\approx\) 34 pm V−1 (theoretical)7 while 4H-SiC features \({\chi }_{{zzz}}^{(2)}\approx\) −23.4 pm V−1 and \({\chi }_{{zxx}}^{(2)}\approx\) 13.0 pm V−1 8 This enables nonlinear and spontaneous quantum light sources based on \({\chi }^{(2)}\) optic processes on integrated SiC-on-insulator (SiCoI) platforms. Compared with the integrated lithium niobate-on-insulator (LNoI) platform, SiC offers process compatibility with the mature wafer-level complementary metal-oxide-semiconductor compatibility (CMOS) processes and an insignificant photorefractive effect9,10,11. Supplementary Table 1 (see Supplementary Note 1) summarizes and compares conventional integrated second-order nonlinear photonic platforms.

We measured durability based on our experiences with each model. We punished these products during the testing period with daily and prolonged use over multiple ski seasons when possible. We also utilized valuable input from dozens of other users and OutdoorGearLab friends.

Li, J. & Poon, A. W. Time-bin Entanglement Based on Integrated 3C-SiC-on-insulator Photon-pair Sources. In Proceedings of CLEO (San Jose, USA, 2023).

While other gloves provide an extensive set of features, these gloves have only a nose wipe and a keeper clip. While this might not seem like much, we found that these are the only features we really need in the backcountry. They are also surprisingly durable, given their soft leather construction. Usually, our professional testers burn through leather gloves quickly, but these gloves are still going strong after an extensive test period. If you're in the market for a highly dexterous glove that won't break the bank, check out the Hestra Ergo Grip Active.

Li, J., Zhang, Q., Wang, J. et al. An integrated 3C-silicon carbide-on-insulator photonic platform for nonlinear and quantum light sources. Commun Phys 7, 125 (2024). https://doi.org/10.1038/s42005-024-01620-x

Romijn, J. et al. Integrated Digital and Analog Circuit Blocks in a Scalable Silicon Carbide CMOS Technology. IEEE Trans. Electron Devices 69, 4–10 (2022).

The Fission SV and Rab Khroma Freeride are the most water-resistant gloves in our review. Their softshell exterior and sturdy leather easily repel water droplets, and their Gore-Tex membranes prevent any water from penetrating the interior of the glove. A large gauntlet and cinch cord further sealed out the elements. We were also impressed by the weather resistance of the Black Diamond Guide. The Montana and Mercury mitts also performed well during water resistance testing and kept water out completely.

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The major downside of mittens is that you can't use your individual fingers, and these mitts are not outliers here. The Mercury Mitts have the worst dexterity of any model we tested. When warmth is the main concern, dexterity might take a backseat, but these mitts are hard to use for even the most basic tasks, like zipping up a jacket or buckling boots. They don't come with a wrist leash, which means they can potentially be lost when taken off, which is bound to happen often due to their lack of dexterity. Still, most folks seek mittens because they find gloves too cold. If that's you, these are the best mittens we've ever tested. If you can tolerate less water resistance and want to save money, check out the The North Face Montana Ski Mitts below.

Scanning electron microscopy (SEM) images of (a) the device, (b) the zoom-in view of the sidewall, and of (c) the cross-sectional view of the waveguide end-facet. d Near-field image of the TM20 mode. e Corresponding lens-to-lens normalized transmission spectra of the device for 780 nm wavelengths (red) and 1550 nm wavelengths (black). f Zoom-in view of the aligned resonances with a Lorentzian resonance lineshape fitting of the NIR resonance. g Measured pump (black) and second-harmonic generation (SHG) (red) spectra. Inset: Top-view scattering of the SHG light. h Measured and fitted pump-to-SHG power dependence in a log-log scale.

Yamaoka, S. et al. Directly modulated membrane lasers with 108 GHz bandwidth on a high-thermal-conductivity silicon carbide substrate. Nat. Photonics 15, 28–35 (2021).

In general, the less expensive gloves have less of a focus on durability and dexterity in their materials and construction. When treated properly, real leather should last longer than synthetic fabrics, especially in high-use areas like the palms and fingertips. Genuine leather is also more expensive, which means you'll have to pay more for higher-quality gloves. Warmth is usually correlated with price, as more insulation makes a glove more expensive. Water resistance can be achieved without using expensive Gore-Tex or similar membranes, although, in general, Gore-Tex gloves proved more weatherproof in our tests than the less expensive alternatives.

While most ski gloves will have some level of waterproofing, deciding how much is necessary will largely depend on your climate and use on the hill. For those in wetter climates, a good pair of Gore-Tex style gloves becomes necessary, while someone in a drier climate may opt for more insulation than ultimate waterproofing. To narrow your choices, consider your climate and how much time you spend using your gloves in the snow, whether working or playing.

Ski gloves come in various natural and synthetic materials, the main idea being protection from the elements. Leather is great for its durability but takes more maintenance to keep its waterproofing. For those who work in their gloves, leather is a popular choice, but synthetics tend to offer more dexterity and can provide better breathability. Synthetic gloves are often cheaper than high-quality leather gloves but typically don't last as long. If you're having a hard time choosing between the two, consider how important the longevity of your gloves is and how often you plan on using them. Leather will work best as a daily driver, but synthetic is cheaper and can be just as waterproof in many cases.

Li, J. & Poon, A. W. A 3C-SiC-on-Insulator-Based Integrated Photonic Platform Using an Anodic Bonding Process with Glass Substrates. Micromachines 14, 399 (2023).

Yamada, S. et al. Second-harmonic generation in a silicon-carbide-based photonic crystal nanocavity. Opt. Lett. 39, 1768 (2014).

We have very few complaints about the Fission SV. It doesn't have an adjustable wrist cinch strap and has only an internal elastic wrist strap to keep the glove tight on the hand. Our testers also found that this glove runs slightly large, so unless you plan to wear a thin liner underneath, we recommend purchasing a size down from your regular glove size. The Fission SV is a great glove for most skiers and riders who demand the utmost weather resistance and dexterity. They are also perfect for snowshoeing and cold urban travel. The one metric they didn't blow us away with was warmth. If warmth is your main concern, check out the Outdoor Research Prevail Heated Gore-Tex Gloves. They have much lower dexterity than the Fission but are heated to keep your hands extra toasty.

Lukin, D. M. et al. 4H-silicon-carbide-on-insulator for integrated quantum and nonlinear photonics. Nat. Photonics 14, 330–334 (2020).

To find the best ski gloves and mitts available, we started by digging deep into the market. After extensive research of high-quality and popular gloves, we purchased the most intriguing models and sent them to our expert testers. Then we thoroughly used and evaluated each pair and scored them in key performance metrics. We tested warmth by riding chairlifts and skiing in the Cascades, Alps, Wasatch, British Columbia, Jackson Hole, and Northeast US, as well as working in the field with avalanche forecasting teams. We tested dexterity by buckling our boots, writing notes with the gloves on, tying boot laces, and unlocking car doors. We also tested water resistance by dunking the gloves in a bucket of water for two minutes and comparing the results. For more about our testing, see our How We Test article.

Severino, A. 3C-SiC epitaxial growth on large area silicon: Thin films. Silicon Carbide Epitaxy 37, 145–191 (2012).

Zielinski, M. et al. Structural Quality, Polishing and Thermal Stability of 3C-SiC/Si Templates. Mater. Sci. Forum 924, 306–309 (2018).

a Measured single-photon flux detected by the SNSPDs with different DWDM channels. SNSPDs: superconducting nanowire single-photon detectors. DWDM channels: dense wavelength-division multiplexed channels. FSR: free spectral range. b, c Measured histograms of the relative arrival times of the first adjacent resonances at 1569/1581 nm and of the second adjacent resonances at 1563/1588 nm, respectively. The histograms are measured multiple times to obtain the error bars for all the bins. Measured power dependence of: (d) the single-channel counts, (e) the photon-pair coincidence counts, (f) the estimated PGRs, and of (g) the estimated CARs. The error bars are the standard deviations of (b–e) the coincidence counts, (f) PGRs and of (g) CARs.

In this work, we adopted the 3C-SiC as this is the only polytype that is epitaxially grown on wafer-scale silicon substrates. This is promising for future large-scale integration and wafer-scale fabrication. Moreover, an epitaxially grown 3C-SiC layer features a well-controlled thickness, which minimizes the non-uniformity in the SiC film thickness and avoids the material waste during the grinding process which is unavoidable in the case of utilizing a bulk 4H-SiC substrate20. We demonstrate on our 3C-SiCoI platform through anodically bonding the 3C-SiC film onto a glass substrate (see Methods). We design a waveguide-coupled elliptical microring resonator using type-I (signal and idler are linearly polarized orthogonally to the pump) MPM for \({\chi }^{(2)}\)-based nonlinear and quantum light sources. We design for the conversion between 780 nm near-visible wavelengths and the 1550 nm near-infrared (NIR) wavelengths. We demonstrate an SHG conversion efficiency of 17.4 ± 0.2% W−1 and difference-frequency generation (DFG) with a non-degenerate signal-idler bandwidth of up to 97 nm. We observe DFG across a bandwidth of 9.5 nm around pumping in the 780 nm wavelengths. We demonstrate a SPDC source with a photon-pair generation rate (PGR) of 4.8 MHz and a coincidence-to-accidental ratio (CAR) of \(3361\pm 84\) at an on-chip pump power of 5 mW. At this pump power, we obtain a low heralded single-photon second-order coherence \({g}_{H}^{\left(2\right)}=0.0007\) with a confidence interval of (0.0001, 0.002) with 68% confidence level using these photon-pairs. We generate a time-bin entanglement with a visibility of \(86.0\pm 2.4 \%\) in a free-space Franson interferometer23 using our photon-pair source, which was reported recently24. Our work shows the feasibility of SiC-based on-chip nonlinear and quantum light sources based on \({\chi }^{(2)}\) nonlinearity.

We fabricate the devices on the same integrated 3C-SiCoI platform as described in9. We use the commercially available polished 4” (001) 3C-SiC-on-Si wafers from NOVASIC. Before the wafer bonding, we deposit a layer of plasma-enhanced chemical vapor deposition (PECVD) SiO2 with a thickness of 500 nm on the 3C-SiC-on-Si dies (1 × 1 cm) to serve as a high-quality under-cladding layer. The PECVD recipe features SiH4 and N2O gas flows of 15 and 1410 sccm, respectively. The chamber is heated to 300 °C and kept at a pressure of 900 mTorr. The coil power is 30 W. We use the Karl Suss SB6 wafer bonder for the anodic bonding process between the dies and the soda lime glass substrate. We attain the bonding under 380 °C in a vacuum environment and upon an applied voltage of 1000 V. We use the standard 25% tetramethylazanium hydroxide solution to completely remove the silicon substrate at 80 °C and to expose the 3C-SiC film. The thickness of the 3C-SiC film is 1.5 μm initially. We thin down the film to our targeted thickness of ~800 nm by deep reactive ion etching (DRIE) process. The etching chemistry adopts SF6 and O2 gases with flows of 25 and 5 sccm, respectively. We kept the chamber pressure at 10 mTorr. The coil power and the platen power are 800 and 250 W, respectively. We then deposit a layer of the PECVD SiO2 as the hard mask. We pattern it with electron-beam lithography and with a standard SiO2 dry etching process available in the cleanroom. This SiO2 hardmask etching recipe adopts C4F8 and H2 gases with gas flows of 12 and 8 sccm, respectively. We kept the chamber pressure at 4 mTorr. The coil power and the platen power are 925 and 130 W, respectively. Then, we use the same SF6-based etching chemistry as in the film thinning-down process to dry etch the 3C-SiC patterns. To attain a steep sidewall slope, we add 3 s of C4H8 passivation steps after 5 s of dry etching steps to protect the waveguide sidewalls. The gas flow of C4H8 is 40 sccm and the coil power is 200 W. We recorded an etching selectivity of 3C-SiC:SiO2 ≈ 1.45. Afterwards, we deposit a layer of PECVD SiO2 with a thickness of 500 nm as the upper-cladding layer. Finally, we cleave the chip to expose the waveguide end-facets for coupling using long-working-distance (LWD) objective lenses.

One of the biggest drawbacks of any mitten is lack of dexterity, and the Montana Ski Mitts are among the least dexterous models we've tested. Due to their design and relative bulk, you'll probably have to remove these mitts for virtually any tasks involving fine motor skills. That said, most folks seeking the warmth and comfort of a mitten are aware of this and willing to accept the tradeoff in dexterity for happy hands. Either way, these are a great pair of mittens that will keep your digits toasty on the coldest days without breaking the bank. If you're in the market for a basic version that's even more affordable than these, check out the Flylow Oven Mitt.

Luo, R. et al. Optical Parametric Generation in a Lithium Niobate Microring with Modal Phase Matching. Phys. Rev. Appl. 11, 1 (2019).

To demonstrate the potential of building a quantum system based on our 3C-SiCoI platform, we examine time-bin entanglement using our photon-pair sources. Entangled photon-pairs constitute many quantum-enabled technologies, including quantum computing and quantum cryptography42. Among various physical dimensions for entanglement, time-bin entanglement is more robust to perturbations when the photons propagate in fiber networks42,43,44,45.

This one was pretty easy to determine. We found the Black Diamond Mercury Mitt to be the top dog by a wide margin. The North Face Montana Mitt is nearly on par in terms of warmth with a similar overall design, lofty insulation, and cozy fleece lining. Both mitten options are warmer than most of the unheated glove options.

We demonstrated experimentally that our integrated 3C-SiCoI photonic platforms enable nonlinear and quantum light sources using waveguide-coupled elliptical microring cavities. We realized quantum interference systems, namely, time-bin entanglement using our photon-pair sources. By exploiting a wafer-scale bonding process, we envision the feasibility to fabricate on a chip large-scale-integrated cavities and on-chip interferometers. Our work thus paves the way toward future large-scale-integrated on-chip nonlinear and quantum photonic circuits based on this CMOS-compatible second-order nonlinear photonic platform. Besides, the recently demonstrated Pockels-effect-based 3C-SiC optical modulator21 can be integrated on the same quantum photonic chip to provide even more complex quantum state manipulation functionalities. Our measured SHG conversion and pair-generation generation efficiencies are, however, still below those state-of-the-art values from other on-chip second-order nonlinear photonic platforms, including LNoI38, GaAs36 and 4H-SiC19. The work reported in those platforms are based on resonators supporting loaded Q factors of \({10}^{5} \sim {10}^{6}\). We attribute our limited \({Q \sim 10}^{4}\) to our un-optimized fabrication process, where the waveguide sidewall roughness resulting from the dry etching causes significant scattering losses. Given our near-vertical waveguide sidewall slope of \(86^{\circ}\), we can fabricate thicker 3C-SiC devices with a wider waveguide width, which can increase the waveguide confinement and reduce the sidewall scattering loss. The scattering losses caused by the crystal lattice defects within the 3C-SiC film can limit the cavity Q factor as well. Those defects are generated during the epitaxial process because of the large (20%) lattice mismatch between the 3C-SiC and the Si substrates. We can mitigate this issue by adopting thicker epitaxial layers, which relax the crystal lattice defects due to the lattice mismatch gradually with the film thickness46,47,48, and by thinning down the films to the target thickness while removing the high-density crystal defects near the interface with the Si substrate.”

We must account for the \(\bar{4}3m\) crystal point-group symmetry of 3C-SiC32 for designing a microring cavity. When the three mixing fields propagate in an arbitrary direction within the (001) 3C-SiC film, the projection of the field of the TE-mode onto the x- and y-crystal axes results in an angle-dependent effective susceptibility \({\chi }_{{eff}}^{(2)}=\cos \varphi \,\sin \varphi \,{\chi }_{{zxy}}^{(2)}\)33. The \({\chi }_{{eff}}^{(2)}\) is optimized with the waves propagating in directions \(45^\circ /135^\circ\) between the x- and y-crystal axes. The nonlinear polarization of a \(\bar{4}3m\) crystal has a \(\pi\)-phase flip with the wave propagation directions rotated by \(90^\circ\). While we may leverage this characteristic property to attain \(\bar{4}\)-QPM, as theoretically studied and experimentally demonstrated in compound III-V material systems featuring the \(\bar{4}3m\) crystal symmetry34,35,36, this method typically imposes a few-micron cavity size for microdisk resonators which may limit the Q factor34,35. The design principle also involves careful alignment of resonances with a certain mode-order difference34,35,36. These impose an overall tight tolerance for device fabrication. Figure 1c schematically illustrates our mitigation of adopting an elliptical cavity. In our scheme, to attain efficiently phase-matched nonlinear processes within microring cavities, we designed an elliptical microring cavity, with a major-to-minor-axes aspect ratio of 2 to increase the MPM interaction length along the flat arc waveguide in one \(90^{\circ}\) rotation of the fields while decreasing the reverse conversion around the two high-curvature poles. We adopted a semi-major axis \(a=30\mu m\) and a semi-minor axis \(b=15\mu m\), which corresponds to a circumference \(L=145\mu m\), to enable a smaller mode volume compared with mm-sized cavities.

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Fiorentino, M. et al. Spontaneous parametric down-conversion in periodically poled KTP waveguides and bulk crystals. Opt. Express 15, 7479–7488 (2007).

Silicon carbide (SiC) polytypes are emerging for integrated nonlinear and quantum photonics due to their wide-bandgap energies, second-order optic nonlinearity and process compatibility with complementary metal-oxide-semiconductor technologies. Among polytypes, 3C-SiC is the only one epitaxially grown on wafer-scale silicon substrates. However, on-chip nonlinear and quantum light sources leveraging the second-order nonlinearity of 3C-SiC have not been reported to our knowledge. Here, we design and fabricate an elliptical microring on 3C-SiC. We demonstrate a nonlinear light source with a second-harmonic generation efficiency of \(17.4\pm 0.2 \% {W}^{-1}\) and difference-frequency generation with a signal-idler bandwidth of 97 nm. We demonstrate a spontaneous parametric down-conversion source with a photon-pair generation rate of 4.8 MHz and a coincidence-to-accidental ratio of \(3361\pm 84\). We measure a low heralded single-photon second-order coherence \({g}_{H}^{\left(2\right)}=0.0007\). We observe time-bin entanglement with a visibility of \(86.0\pm 2.4 \%\) using this source. Our work paves a way toward SiC-based on-chip nonlinear and quantum photonic circuits.

Are you seeking the best ski gloves for your snow adventures? We have tested 74 pairs in the last eleven years. For this update, we pit 22 top gloves and mittens for skiing and snowboarding against each other. Our experts took these models on snow for rigorous examination. The trial grounds are the same places you will use your gloves — ski resorts, backcountry laps, cross-country, on snowmobiles, and ski mountaineering missions spanning across the US, Canada, and Europe. We also put them through controlled temperature and water-resistance tests. Hands-on experience with each pair informs our assessments, focusing on the areas of performance you care about most.

where \({\epsilon }_{0}\) is the vacuum permittivity and \({\epsilon }_{1(2)}=6.55(6.81)\) is the relative permittivity of 3C-SiC at 1550 nm and 780 nm11, respectively (See Supplementary Note 8 for details). We estimate a nonlinear coupling of \(\gamma \,\approx \,7.6\times {10}^{5}{Hz}\). From (1), assuming a double-resonance condition, we assume \({\varDelta \omega }_{1(2)} \,\ll \,{\kappa }_{1,t}\). Given our measured loaded-Q factors at 1550 nm and 780 nm and assuming an external coupling \({\kappa }_{1(2),e} \,\approx \,{\kappa }_{1(2),t}/2\) we theoretically estimated \({\eta }_{{SHG}} \,\approx \,19 \% {W}^{-1}\), which is consistent with our experimental estimation.

Niedermeier, S., Schillinger, H., Sauerbrey, R., Adolph, B. & Bechstedt, F. Second-harmonic generation in silicon carbide polytypes. Appl. Phys. Lett. 75, 618–620 (1999).

where \({\omega }_{1(2)}\), \({\kappa }_{1(2),t}\), \({\kappa }_{1(2),e}\) and \({\varDelta \omega }_{1(2)}\) are the angular frequencies, the cavity total loss rates, the cavity external coupling rates and the angular frequency detuning from the cavity resonances of the 1575 nm pump (SHG) waves. The nonlinear coupling coefficient \(\gamma\) is given by:

We were disappointed in the Black Diamond Legend's durability, which has incredibly supple palm leather, but wore down and developed holes quickly. This was a bummer because if the leather were a bit more durable, the Legend would be a top contender.

We accumulate more than 6 h of data (40 Gb) and obtain only 1 triple coincidence count \({N}_{{s}_{1}{s}_{2}i}\) while collecting \({N}_{{s}_{1}i}={{{{\mathrm{1,949,638}}}}}\), \({N}_{{s}_{2}i}={{{{\mathrm{441,670}}}}}\) and \({N}_{i}={{{{\mathrm{610,078,920}}}}}\). Assuming a Poissonian distribution40 of the triple coincidence event, we estimate a low \({g}_{H}^{(2)}\) = 0.0007 and a confidence interval of (0.0001, 0.002) within approximately one standard deviation. This is one order of magnitude below recently reported work using second- and third-order SPDC processes38,39,40,41. Hence, our device can function as low-noise heralded single-photon sources.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Communications Physics thanks Florian Kaiser and the other anonymous, reviewer(s) for their contribution to the peer review of this work.

Many manufacturers now offer gloves that produce heat electronically instead of solely retaining your hand's natural warmth. We've tested several over the years, and the Outdoor Research Prevail Heated is our current favorite. These kinds of gloves usually have three heat settings. The lowest settings generally last all day on a full charge, while the highest setting usually drained the batteries within a couple of hours during our tests. Heated gloves are able to take our hands from numb to warm in a matter of minutes at the press of a button. Some of our testers preferred to blast the heater on high for a few minutes and then turn them off to save battery power.

The Hestra Ergo Grip Active easily wins the dexterity category with its thin fingers and nonexistent insulation. This glove is specific for backcountry users on the warmest days of the ski season. We also love the Black Diamond Tour for dexterity, which features excellent tailoring and soft leather for ideal grip. The Hestra Leather Fall Line also provides plenty of dexterity and slightly more insulation. We were impressed by the dexterity of the relatively warm Black Diamond Legend, but the supple leather on the fingers and palm wore out quickly. The Fission SV is close behind, with great dexterity and none of the aforementioned downsides. That balance is a significant reason why the Fission SV is our top choice overall.

Jiang, X., Wu, H. & Dai, D. Low-loss and low-crosstalk multimode waveguide bend on silicon. Opt. Express 26, 17680 (2018).

Wang, L. et al. Growth of 3C-SiC on 150-mm Si (100) substrates by alternating supply epitaxy at 1000 °C. Thin Solid Films 519, 6443–6446 (2011).

Wang, C. et al. High-Q microresonators on 4H-silicon-carbide-on-insulator platform for nonlinear photonics. Light Sci. Appl. 10, 139 (2021).

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a–f Measured difference-frequency generation (DFG) spectra with different input pump and signal resonances. Different colors represent various groups of pump, signal and generated idler wavelengths. g Scatter plot of the triple-resonance-enhanced DFG modes. The region between the two dashed lines corresponds to the simulated MPM zone in Fig. 2d. h Measured power-dependence of the DFG with varying pump and observed signal powers.

Phones are now baked into our daily lives, and the glove market has recognized that many people are using their phones on the slopes and have started providing touchscreen-compatible gloves. The liners of the Dakine Titan are touchscreen compatible. Many gloves claim to include sensitive pads on the tips of the forefingers, but in our tests, cold phone screens and even colder gloves had a hard time getting along.

Lady shredders, check out our review of the best women's ski gloves. Whether you're searching for the best snowboard or accessorizing with the best ski jacket, a new pair of ski goggles, the top-rated ski helmet, or a pair of the best skis on the market, our extensive reviews of ski and snow sports gear can help take the guesswork out of your purchases.

Martini, F. & Politi, A. Four wave mixing in 3C SiC ring resonators. Appl. Phys. Lett. 112, 1–5 (2018).

Aside from the fabric itself, water can also enter a glove through the wrist opening. Most gloves in our review feature a large wrist gauntlet with a drawstring closure that overlaps with a jacket's wrist cuff, making a formidable defense against water trying to enter the glove. This gauntlet, as seen on the Mercury Mitt, BD Guide, Fission SV, Rab Khroma, Swany X-Change, and OR Prevail, can be worn on the outside or the inside of a jacket sleeve.

Wu, I. J. & Guo, G. Y. Second-harmonic generation and linear electro-optical coefficients of SiC polytypes and nanotubes. Phys. Rev. B Condens. Matter Mater. Phys. 78, 1–10 (2008).

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