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Validation of aerosol backscatter profiles from Raman lidar and ceilometer using balloon-borne measurements 期刊论文
Atmospheric Chemistry and Physics, 2020
作者:  Simone Brunamonti, Giovanni Martucci, Gonzague Romanens, Yann Poltera, Frank G. Wienhold, Alexander Haefele, and Francisco Navas-Guzmán
收藏  |  浏览/下载:13/0  |  提交时间:2020/05/13
Massively parallel coherent laser ranging using a soliton microcomb 期刊论文
NATURE, 2020, 581 (7807) : 164-+
作者:  Casanova, Emmanuelle;  Knowles, Timothy D. J.;  Bayliss, Alex;  Dunne, Julie;  Baranski, Marek Z.;  Denaire, Anthony;  Lefranc, Philippe;  di Lernia, Savino;  Roffet-Salque, Melanie;  Smyth, Jessica;  Barclay, Alistair;  Gillard, Toby;  Classen, Erich;  Coles, Bryony;  Ilett, Michael;  Jeunesse, Christian;  Krueger, Marta;  Marciniak, Arkadiusz;  Minnitt, Steve;  Rotunno, Rocco;  van de Velde, Pieter;  van Wijk, Ivo;  Cotton, Jonathan;  Daykin, Andy;  Evershed, Richard P.
收藏  |  浏览/下载:46/0  |  提交时间:2020/07/03

Coherent ranging, also known as frequency-modulated continuous-wave (FMCW) laser-based light detection and ranging (lidar)(1) is used for long-range three-dimensional distance and velocimetry in autonomous driving(2,3). FMCW lidar maps distance to frequency(4,5) using frequency-chirped waveforms and simultaneously measures the Doppler shift of the reflected laser light, similar to sonar or radar(6,7) and coherent detection prevents interference from sunlight and other lidar systems. However, coherent ranging has a lower acquisition speed and requires precisely chirped(8) and highly coherent(5) laser sources, hindering widespread use of the lidar system and impeding parallelization, compared to modern time-of-flight ranging systems that use arrays of individual lasers. Here we demonstrate a massively parallel coherent lidar scheme using an ultra-low-loss photonic chip-based soliton microcomb(9). By fast chirping of the pump laser in the soliton existence range(10) of a microcomb with amplitudes of up to several gigahertz and a sweep rate of up to ten megahertz, a rapid frequency change occurs in the underlying carrier waveform of the soliton pulse stream, but the pulse-to-pulse repetition rate of the soliton pulse stream is retained. As a result, the chirp from a single narrow-linewidth pump laser is transferred to all spectral comb teeth of the soliton at once, thus enabling parallelism in the FMCW lidar. Using this approach we generate 30 distinct channels, demonstrating both parallel distance and velocity measurements at an equivalent rate of three megapixels per second, with the potential to improve sampling rates beyond 150 megapixels per second and to increase the image refresh rate of the FMCW lidar by up to two orders of magnitude without deterioration of eye safety. This approach, when combined with photonic phase arrays(11) based on nanophotonic gratings(12), provides a technological basis for compact, massively parallel and ultrahigh-frame-rate coherent lidar systems.


  
Observation of topologically enabled unidirectional guided resonances 期刊论文
NATURE, 2020, 580 (7804) : 467-+
作者:  Wang, Renjing;  Wang, Shengliu;  Dhar, Ankita;  Peralta, Christopher;  Pavletich, Nikola P.
收藏  |  浏览/下载:6/0  |  提交时间:2020/07/03

Unidirectional radiation is important for various optoelectronic applications, such as lasers, grating couplers and optical antennas. However, almost all existing unidirectional emitters rely on the use of materials or structures that forbid outgoing waves-that is, mirrors, which are often bulky, lossy and difficult to fabricate. Here we theoretically propose and experimentally demonstrate a class of resonances in photonic crystal slabs that radiate only towards one side of the slab, with no mirror placed on the other side. These resonances, which we name '  unidirectional guided resonances'  , are found to be topological in nature: they emerge when a pair of half-integer topological charges(1-3) in the polarization field bounce into each other in momentum space. We experimentally demonstrate unidirectional guided resonances in the telecommunication regime by achieving single-side radiative quality factors as high as 1.6 x 10(5). We further demonstrate their topological nature through far-field polarimetry measurements. Our work represents a characteristic example of applying topological principles(4,5) to control optical fields and could lead to energy-efficient grating couplers and antennas for light detection and ranging.


Unidirectional radiation is achieved in a photonic crystal slab without the use of mirrors by merging a pair of topological defects carrying half-integer charges.


  
Global satellite-observed daily vertical migrations of ocean animals 期刊论文
Nature, 2019, 576: 257-261
作者:  Michael J. Behrenfeld;  Peter Gaube;  Alice Della Penna;  Robert T. O鈥橫alley;  William J. Burt;  Yongxiang Hu;  Paula S. Bontempi;  Deborah K. Steinberg;  Emmanuel S. Boss;  David A. Siegel;  Chris A. Hostetler;  Philippe D. Tortell;  Scott C. Doney
收藏  |  浏览/下载:8/0  |  提交时间:2020/04/16
Interacting geomorphic and ecological response of step-pool streams after wildfire 期刊论文
GEOLOGICAL SOCIETY OF AMERICA BULLETIN, 2019, 131: 1480-1500
作者:  Chin, Anne;  39;Dowd, Alison P.
收藏  |  浏览/下载:0/0  |  提交时间:2019/11/27
Postglacial faulting near Crater Lake, Oregon, and its possible association with the Mazama caldera-forming eruption 期刊论文
GEOLOGICAL SOCIETY OF AMERICA BULLETIN, 2019, 131: 1440-1458
作者:  Bacons, Charles R.;  Robinson, Joel E.
收藏  |  浏览/下载:2/0  |  提交时间:2019/11/27
Spatiotemporal light control with frequency-gradient metasurfaces 期刊论文
SCIENCE, 2019, 365 (6451) : 374-+
作者:  Shaltout, Amr M.;  Lagoudakis, Konstantinos G.;  van de Groep, Jorik;  Kim, Soo Jin;  Vuckovic, Jelena;  Shalaev, Vladimir M.;  Brongersma, Mark L.
收藏  |  浏览/下载:6/0  |  提交时间:2019/11/27
Phase-only transmissive spatial light modulator based on tunable dielectric metasurface 期刊论文
SCIENCE, 2019, 364 (6445) : 1087-+
作者:  Li, Shi-Qiang;  Xu, Xuewu;  Veetil, Rasna Maruthiyodan;  Valuckas, Vytautas;  Paniagua-Dominguez, Ramon;  Kuznetsov, Arseniy I.
收藏  |  浏览/下载:3/0  |  提交时间:2019/11/27
Spatial patterning among savanna trees in high-resolution, spatially extensive data 期刊论文
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 2019, 116 (22) : 10681-10685
作者:  Staver, A. Carla;  Asner, Gregory P.;  Rodriguez-Iturbe, Ignacio;  Levin, Simon A.;  Smit, Izak P. J.
收藏  |  浏览/下载:8/0  |  提交时间:2019/11/27
savanna  spatial pattern  LiDAR  heterogeneity  
Morphodynamics of bedrock-influenced dryland rivers during extreme floods: Insights from the Kruger National Park, South Africa 期刊论文
GEOLOGICAL SOCIETY OF AMERICA BULLETIN, 2018, 130: 1825-1841
作者:  Milan, David;  Heritage, George;  Tooth, Stephen;  Entwistle, Neil
收藏  |  浏览/下载:6/0  |  提交时间:2019/04/09