A new aspheric surface pre-collimation lenses system for the optical antenna of three-dimensional （3D） imaging of lidar has been optimally designed and simulated by optical design software CODE-V.Four kinds of asphe...A new aspheric surface pre-collimation lenses system for the optical antenna of three-dimensional （3D） imaging of lidar has been optimally designed and simulated by optical design software CODE-V.Four kinds of aspheric surfaces spherical lenses including the sections of spherical,elliptical,hyperbola,and parabola have been researched.The optical system,including the elliptical cylinder lenses collimation and the optical antenna,can be realized less than 5 rad collimation angle for dot source semiconductor laser beam.展开更多
Optical antennas play a pivotal role in interfacing integrated photonic circuits with free-space systems.Designing antennas for optical phased arrays ideally requires achieving compact antenna apertures,wide radiation...Optical antennas play a pivotal role in interfacing integrated photonic circuits with free-space systems.Designing antennas for optical phased arrays ideally requires achieving compact antenna apertures,wide radiation angles,and high radiation efficiency all at once,which presents a significant challenge.Here,we experimentally demonstrate a novel ultra-compact silicon grating antenna,utilizing subwavelength grating nanostructures arranged in a transversally interleaved topology to control the antenna radiation pattern.Through near-field phase engineering,we increase the antenna’s far-field beam width beyond the Fraunhofer limit for a given aperture size.The antenna incorporates a single-etch grating and a Bragg reflector implemented on a 300-nm-thick silicon-oninsulator(SOI)platform.Experimental characterizations demonstrate a beam width of 44°×52°with−3.22 dB diffraction efficiency,for an aperture size of 3.4μm×1.78μm.Furthermore,to the best of our knowledge,a novel topology of a 2D antenna array is demonstrated for the first time,leveraging evanescently coupled architecture to yield a very compact antenna array.We validated the functionality of our antenna design through its integration into this new 2D array topology.Specifically,we demonstrate a small proof-of-concept two-dimensional optical phased array with 2×4 elements and a wide beam steering range of 19.3º×39.7º.A path towards scalability and larger-scale integration is also demonstrated on the antenna array of 8×20 elements with a transverse beam steering of 31.4º.展开更多
In this paper, an optical beam-former in receiving mode has been proposed and experimentally demonstrated. The requirement in system's hardware has been dramatically reduced using a hybrid approach between dispers...In this paper, an optical beam-former in receiving mode has been proposed and experimentally demonstrated. The requirement in system's hardware has been dramatically reduced using a hybrid approach between dispersive and non-dispersive delay. The proposed system is capable of supporting RF signals from L-band to X-band, with large coverage and strong robustness against the grating's group delay ripples.展开更多
Light detection and ranging(LiDAR)serves as one of the key components in the fields of autonomous driving,surveying mapping,and environment detection.Conventionally,dense points clouds are pursued by LiDAR systems to ...Light detection and ranging(LiDAR)serves as one of the key components in the fields of autonomous driving,surveying mapping,and environment detection.Conventionally,dense points clouds are pursued by LiDAR systems to provide high-definition 3D images.However,the LiDAR is typically used to produce abundant yet redundant data for scanning the homogeneous background of scenes,resulting in power waste and excessive processing time.Hence,it is highly desirable for a LiDAR system to“gaze”at the target of interest by dense scanning and rough sparse scans on the uninteresting areas.Here,we propose a LiDAR structure based on an optical phased array(OPA)with reconfigurable apertures to achieve such a gaze scanning function.By virtue of the cascaded optical switch integrated on the OPA chip,a 64-,128-,192-,or 256-channel antenna can be selected discretionarily to construct an aperture with variable size.The corresponding divergence angles for the far-field beam are 0.32°,0.15°,0.10°,and 0.08°,respectively.The reconfigurable-aperture OPA enables the LiDAR system to perform rough scans via the large beam spots prior to fine scans of the target by using the tiny beam spots.In this way,the OPA-based LiDAR can perform the“gaze”function and achieve full-range scanning efficiently.The scanning time and power consumption can be reduced by 1/4 while precise details of the target are maintained.Finally,we embed the OPA into a frequency-modulated continuous-wave(FMCW)system to demonstrate the“gaze”function in beam scanning.Experiment results show that the number of precise scanning points can be reduced by 2/3 yet can obtain the reasonable outline of the target.The reconfigurable-aperture OPA(RA-OPA)can be a promising candidate for the applications of rapid recognition,like car navigation and robot vision.展开更多
Optical antennas have received considerable attention in recent years due to their unique ability to convert localized energy to freely propagating radiation and vice versa.Sidelobe level(SLL)is one of the most crucia...Optical antennas have received considerable attention in recent years due to their unique ability to convert localized energy to freely propagating radiation and vice versa.Sidelobe level(SLL)is one of the most crucial parameters in antenna design.A low SLL is beneficial to minimize the antenna interference with other optical components.Here a plasmonic optical leaky-wave antenna with low SLL is reported.Shifting spatial frequency by periodically modulating the electric-field amplitude in a plasmonic gap waveguide enables a free-space coupled wave out of the antenna.At the same time,precise control of the aperture fields by the modulation depth allows for reducing SLL.Simulation results indicate that the proposed design can achieve a high directivity of 15.8 dB and a low SLL of-20 dB at the wavelength of 1550 nm.A low SLL below-15 dB is experimentally demonstrated within the wavelength range from 1527 to 1570 nm.In addition,the low-SLL property is further verified by comparing it with a uniformly modulated antenna.By modulating the guided waves in the plasmonic gap waveguide in different forms,the aperture fields can be flexibly arranged to achieve arbitrary wavefront shaping.It bridges the gap between guided and free-space waves and empowers plasmonic integrated devices to control free-space light,thus enabling various free-space functions.展开更多
Electric field is a powerful instrument in nanoscale engineering,providing wide functionalities for control in various optical and solid-state nanodevices.The development of a single optically resonant nanostructure o...Electric field is a powerful instrument in nanoscale engineering,providing wide functionalities for control in various optical and solid-state nanodevices.The development of a single optically resonant nanostructure operating with a charge-induced electrical field is challenging,but it could be extremely useful for novel nanophotonic horizons.Here,we show a resonant metal-semiconductor nanostructure with a static electric field created at the interface between its components by charge carriers generated via femtosecond laser irradiation.We study this field experimentally,probing it by second-harmonic generation signal,which,in our system,is time-dependent and has a non-quadratic signal/excitation power dependence.The developed numerical models reveal the influence of the optically induced static electric field on the second harmonic generation signal.We also show how metal work function and silicon surface defect density for different charge carrier concentrations affect the formation of this field.We estimate the value of optically-generated static electric field in this nanoantenna to achieve≈10^(8)V/m.These findings pave the way for the creation of nanoantenna-based optical memory,programmable logic and neuromorphic devices.展开更多
Long-distance light detection and ranging(LiDAR)applications require an aperture size in the order of 30 mm to project 200–300 m.To generate such collimated Gaussian beams from the surface of a chip,this work present...Long-distance light detection and ranging(LiDAR)applications require an aperture size in the order of 30 mm to project 200–300 m.To generate such collimated Gaussian beams from the surface of a chip,this work presents a novel waveguide antenna concept,which we call an“optical leaky fin antenna,”consisting of a tapered waveguide with a narrow vertical“fin”on top.The proposed structure(operating aroundλ=1.55μm)overcomes fundamental fabrication challenges encountered in weak apodized gratings,the conventional method to create an offchip wide Gaussian beam from a waveguide chip.We explore the design space of the antenna by scanning the relevant cross section parameters in a mode solver,and their sensitivity is examined.We also investigate the dispersion of the emission pattern and angle with the wavelength.The simulated design space is then used to construct and simulate an optical antenna to emit a collimated target intensity profile.Results show inherent robustness to crucial design parameters and indicate good scalability of the design.Possibilities and challenges to fabricate this device concept are also discussed.This novel antenna concept illustrates the possibility to integrate long optical antennas required for long-range solid-state LiDAR systems on a high-index contrast platform with a scalable fabrication method.展开更多
We have reported previously the ultrafast energy transfer process with a time constant of 0.8 ps from a monomeric to a dimeric subunit within a perylenetetracarboxylic diimide trimer, which was derived indirectly from...We have reported previously the ultrafast energy transfer process with a time constant of 0.8 ps from a monomeric to a dimeric subunit within a perylenetetracarboxylic diimide trimer, which was derived indirectly from a model fitting into the transient absorption experimental data. Here we present a direct ultrafast fluorescence quenching measurement by employing fs time-resolved transient fluorescence spectroscopy based on noncollinear optical parametric amplification technique. The rapid decay of the monomer＇s emission due to energy transfer was observed directly with a time constant of about 0.82 ps, in good agreement with the previous result.展开更多
An efficient hybrid method based on the method of moments （MOM） and physical optics （PO） for the analysis of radiation characteristics of an electrically large antenna-radome system is presented. Specifically, MOM...An efficient hybrid method based on the method of moments （MOM） and physical optics （PO） for the analysis of radiation characteristics of an electrically large antenna-radome system is presented. Specifically, MOM is first applied to the antenna to find the current on its surface, and then the equivalent PO currents produced by the antenna radiation are assumed on the radome wall. When the coupling of the PO currents and antenna current is considered, the coupling matrix is divided into a series of partial matrices, in order to deduce the memory requirement and accelerate the evaluation process. Numerical results indicate that the proposed hybrid PO-MOM method is accurate and efficient.展开更多
基金supported by Pre-research Foundation under Grant No. G020104PJ09DZ0246the National Natural Science Foundation of China under Grant No. 11004024
文摘A new aspheric surface pre-collimation lenses system for the optical antenna of three-dimensional （3D） imaging of lidar has been optimally designed and simulated by optical design software CODE-V.Four kinds of aspheric surfaces spherical lenses including the sections of spherical,elliptical,hyperbola,and parabola have been researched.The optical system,including the elliptical cylinder lenses collimation and the optical antenna,can be realized less than 5 rad collimation angle for dot source semiconductor laser beam.
基金National Research Council Canada((CSTIP),(HTSN 624)Technology and Innovation Program)Natural Sciences and Engineering Research Council of Canada.
文摘Optical antennas play a pivotal role in interfacing integrated photonic circuits with free-space systems.Designing antennas for optical phased arrays ideally requires achieving compact antenna apertures,wide radiation angles,and high radiation efficiency all at once,which presents a significant challenge.Here,we experimentally demonstrate a novel ultra-compact silicon grating antenna,utilizing subwavelength grating nanostructures arranged in a transversally interleaved topology to control the antenna radiation pattern.Through near-field phase engineering,we increase the antenna’s far-field beam width beyond the Fraunhofer limit for a given aperture size.The antenna incorporates a single-etch grating and a Bragg reflector implemented on a 300-nm-thick silicon-oninsulator(SOI)platform.Experimental characterizations demonstrate a beam width of 44°×52°with−3.22 dB diffraction efficiency,for an aperture size of 3.4μm×1.78μm.Furthermore,to the best of our knowledge,a novel topology of a 2D antenna array is demonstrated for the first time,leveraging evanescently coupled architecture to yield a very compact antenna array.We validated the functionality of our antenna design through its integration into this new 2D array topology.Specifically,we demonstrate a small proof-of-concept two-dimensional optical phased array with 2×4 elements and a wide beam steering range of 19.3º×39.7º.A path towards scalability and larger-scale integration is also demonstrated on the antenna array of 8×20 elements with a transverse beam steering of 31.4º.
文摘In this paper, an optical beam-former in receiving mode has been proposed and experimentally demonstrated. The requirement in system's hardware has been dramatically reduced using a hybrid approach between dispersive and non-dispersive delay. The proposed system is capable of supporting RF signals from L-band to X-band, with large coverage and strong robustness against the grating's group delay ripples.
基金Program for Jilin University Science and Technology Innovative Research Team(2021TD-39)Jilin Provincial Development and Reform Commission Project(2020C056)+2 种基金Major Scientific and Technological Program of Jilin Province(20210301014GX)National Natural Science Foundation of China(62105173,62105174,61934003,62090054)National Key Research and Development Program of China(2022YFB2804504)。
文摘Light detection and ranging(LiDAR)serves as one of the key components in the fields of autonomous driving,surveying mapping,and environment detection.Conventionally,dense points clouds are pursued by LiDAR systems to provide high-definition 3D images.However,the LiDAR is typically used to produce abundant yet redundant data for scanning the homogeneous background of scenes,resulting in power waste and excessive processing time.Hence,it is highly desirable for a LiDAR system to“gaze”at the target of interest by dense scanning and rough sparse scans on the uninteresting areas.Here,we propose a LiDAR structure based on an optical phased array(OPA)with reconfigurable apertures to achieve such a gaze scanning function.By virtue of the cascaded optical switch integrated on the OPA chip,a 64-,128-,192-,or 256-channel antenna can be selected discretionarily to construct an aperture with variable size.The corresponding divergence angles for the far-field beam are 0.32°,0.15°,0.10°,and 0.08°,respectively.The reconfigurable-aperture OPA enables the LiDAR system to perform rough scans via the large beam spots prior to fine scans of the target by using the tiny beam spots.In this way,the OPA-based LiDAR can perform the“gaze”function and achieve full-range scanning efficiently.The scanning time and power consumption can be reduced by 1/4 while precise details of the target are maintained.Finally,we embed the OPA into a frequency-modulated continuous-wave(FMCW)system to demonstrate the“gaze”function in beam scanning.Experiment results show that the number of precise scanning points can be reduced by 2/3 yet can obtain the reasonable outline of the target.The reconfigurable-aperture OPA(RA-OPA)can be a promising candidate for the applications of rapid recognition,like car navigation and robot vision.
基金National Natural Science Foundation of China(U20A20165)Fundamental Research Funds for the Central Universities(ZYGX2019Z005)City University of Hong Kong(CityU 11212121)。
文摘Optical antennas have received considerable attention in recent years due to their unique ability to convert localized energy to freely propagating radiation and vice versa.Sidelobe level(SLL)is one of the most crucial parameters in antenna design.A low SLL is beneficial to minimize the antenna interference with other optical components.Here a plasmonic optical leaky-wave antenna with low SLL is reported.Shifting spatial frequency by periodically modulating the electric-field amplitude in a plasmonic gap waveguide enables a free-space coupled wave out of the antenna.At the same time,precise control of the aperture fields by the modulation depth allows for reducing SLL.Simulation results indicate that the proposed design can achieve a high directivity of 15.8 dB and a low SLL of-20 dB at the wavelength of 1550 nm.A low SLL below-15 dB is experimentally demonstrated within the wavelength range from 1527 to 1570 nm.In addition,the low-SLL property is further verified by comparing it with a uniformly modulated antenna.By modulating the guided waves in the plasmonic gap waveguide in different forms,the aperture fields can be flexibly arranged to achieve arbitrary wavefront shaping.It bridges the gap between guided and free-space waves and empowers plasmonic integrated devices to control free-space light,thus enabling various free-space functions.
基金This research was supported by Priority 2030 Federal Academic Leadership Program,the lithography fabrication of the hybrid nanostructures,studies of linear and nonlinear optical properties were supported by the Russian Science Foundation(Project No.22-72-10035,https://rscf.ru/project/22-72-10035/)the studies of the metal-semiconductor interface of the nanoantenna were supported by the Ministry of Science and Higher Education of the Russian Federation(Project No.075‐15‐2021‐592).
文摘Electric field is a powerful instrument in nanoscale engineering,providing wide functionalities for control in various optical and solid-state nanodevices.The development of a single optically resonant nanostructure operating with a charge-induced electrical field is challenging,but it could be extremely useful for novel nanophotonic horizons.Here,we show a resonant metal-semiconductor nanostructure with a static electric field created at the interface between its components by charge carriers generated via femtosecond laser irradiation.We study this field experimentally,probing it by second-harmonic generation signal,which,in our system,is time-dependent and has a non-quadratic signal/excitation power dependence.The developed numerical models reveal the influence of the optically induced static electric field on the second harmonic generation signal.We also show how metal work function and silicon surface defect density for different charge carrier concentrations affect the formation of this field.We estimate the value of optically-generated static electric field in this nanoantenna to achieve≈10^(8)V/m.These findings pave the way for the creation of nanoantenna-based optical memory,programmable logic and neuromorphic devices.
基金European Research Council(725555,PhotonicSWARM)。
文摘Long-distance light detection and ranging(LiDAR)applications require an aperture size in the order of 30 mm to project 200–300 m.To generate such collimated Gaussian beams from the surface of a chip,this work presents a novel waveguide antenna concept,which we call an“optical leaky fin antenna,”consisting of a tapered waveguide with a narrow vertical“fin”on top.The proposed structure(operating aroundλ=1.55μm)overcomes fundamental fabrication challenges encountered in weak apodized gratings,the conventional method to create an offchip wide Gaussian beam from a waveguide chip.We explore the design space of the antenna by scanning the relevant cross section parameters in a mode solver,and their sensitivity is examined.We also investigate the dispersion of the emission pattern and angle with the wavelength.The simulated design space is then used to construct and simulate an optical antenna to emit a collimated target intensity profile.Results show inherent robustness to crucial design parameters and indicate good scalability of the design.Possibilities and challenges to fabricate this device concept are also discussed.This novel antenna concept illustrates the possibility to integrate long optical antennas required for long-range solid-state LiDAR systems on a high-index contrast platform with a scalable fabrication method.
基金This work was supported by the National Natural Science Foundation of China （No.20925313 and No.60438020）, the National Basic Research Program of China （No.2009CB929404）, and the Chinese Academy of Sciences Innovation Program （KJCX2-YW-W25）.
文摘We have reported previously the ultrafast energy transfer process with a time constant of 0.8 ps from a monomeric to a dimeric subunit within a perylenetetracarboxylic diimide trimer, which was derived indirectly from a model fitting into the transient absorption experimental data. Here we present a direct ultrafast fluorescence quenching measurement by employing fs time-resolved transient fluorescence spectroscopy based on noncollinear optical parametric amplification technique. The rapid decay of the monomer＇s emission due to energy transfer was observed directly with a time constant of about 0.82 ps, in good agreement with the previous result.
基金the National Natural Science Foundation of China (60471040)
文摘An efficient hybrid method based on the method of moments （MOM） and physical optics （PO） for the analysis of radiation characteristics of an electrically large antenna-radome system is presented. Specifically, MOM is first applied to the antenna to find the current on its surface, and then the equivalent PO currents produced by the antenna radiation are assumed on the radome wall. When the coupling of the PO currents and antenna current is considered, the coupling matrix is divided into a series of partial matrices, in order to deduce the memory requirement and accelerate the evaluation process. Numerical results indicate that the proposed hybrid PO-MOM method is accurate and efficient.
