Design and Realization of Phased Array Radar Optical Fiber Transmission System

One optical fiber transmission system is designed. The modularization optical fiber transmission adapters were utilized in the system, so the system structure could be flexibly sealable. The sub-array adapter and signal processor adapter were designed and realized utilizing the new field programmable gate array （FP- GA） which could drive the optical transceiver. The transmission agreement was designed based on the data stream. In order to solve the signal synchronization problem of the optical fiber transmitted phased array radar, a method named synchronous clock was designed. The fiber transmission error code rate of the system was zero with an experimental transmission velocity of 800 Mbit/s. The phased array radar system has detected the airplane target, thus validated the feasibility of the design method.

Beam Steering Analysis in Optically Phased Vertical Cavity Surface Emitting Laser Array

Beam steering in implant defined coherently coupled vertical cavity surface emitting laser （VCSEL） arrays is simulated using the FDTD solution software. Angular deflection dependent on relative phase differences among elements, inter-element spacing, element size and emitted wavelength is analyzed detailedly and systematically. We design and fabricate 1×2 implant defined VCSEL arrays for optimum beam steering performance. Electroni- cally controlled beam steering with a maximum deflection angle of 1.6° is successfully achieved in the 1 × 2 VCSEL arrays. The percentage of the power in the central lobe is above 39% when steering. The results show that the steering is controllable. Compared with other beam steering methods, the fabrication process is simple and of low cost.

Comparative Study on Beam Broadening in Optically Controlled and Conventional Phased Array

The bandwidth characteristic of phased array antenna can be represented by the extent of beam broadening as signal bandwidth is increased. By using two kinds of bandpass signals, the beam 3dB-width values for a variety of instantaneous bandwidths in conventional phased array and wide band optically phased array are respectively analyzed and simulated based on both of their models. And some corresponding curves are given.

High-power mode-programmable orbital angular momentum beam emitter with an internally sensed optical phased array

The high-power mode-programmable orbital angular momentum(OAM)beam has attracted significant attention in a wide range of applications,such as long-distance optical communication,nonlinear frequency conversion,and beam shaping.Coherent beam combining(CBC)of an optical phased array(OPA)can offer a promising solution for both generating the high-power OAM beam and rapidly switching the OAM modes.However,achieving real-time phase noise locking and formation of desired phase structures in a high-power CBC system faces significant challenges.Here,an internal phase-sensing technique was utilized to generate the high-power OAM beam,which effectively mitigated thermal effects and eliminated the need for large optical devices.An OPA with six elements was employed for experimental demonstration.The first effective generation of over 1.5 kW mode-programmable OAM beam in a continuous-wave domain was presented.Moreover,the results demonstrated that the generated OAM beam could be modulated with multiple dimensions.The topological charge can be switched in real time from-1 to-2.Notably,this OAM beam emitter could function as an OAM beam copier by easily transforming a single OAM beam into an OAM beam array.More importantly,a comprehensive analysis was conducted on power scaling,mode switching speed,and expansion of OAM modes.Additionally,the system’s compact design enabled it to function as a packageable OAM beam emitter.Owing to the advantages of having high power and programmable modes with multiple dimension modulation in phase structures and intensity distribution,this work can pave the way for producing high-power structured light beams and advancing their applications.

Independent dual beams generated by array element division in integrated optical phased arrays

Optical phased arrays(OPAs)have broad application prospects due to their advanced capability in beamforming and steering.In this work,we achieve independent dual beams in the far field by dividing the array elements of the OPA,with the maximum scanning range reaching 100°.Based on the working principle of OPAs,theoretical considerations of such multibeam generation are presented.A phase data allocation approach for OPAs in the presence of fabrication-induced random phase variation is developed.Simulations of large ensembles of OPAs with various levels of random residual phase errors have been conducted to help analyze the results.This approach can help OPAs realize multi-beams for light detection and ranging(LiDAR).

Hybrid Optical Beam-Former in Receiver Mode

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.

Intelligent Space All-Optical Network Technology

Microwave transmission in a space network is greatly restricted due to precious radio spectrum resources. To meet the demand for large-bandwidth, global seamless coverage and on-demanding access, the Space All-Optical Network(SAON) becomes a promising paradigm. In this paper, the related space optical communications and network programs around the world are first briefly introduced. Then the intelligent Space All-Optical Network(i-SAON), which can be deemed as an advanced SAON, is illustrated, with the emphasis on its features of high survivability, sensing and reconfiguration intelligence, and large capacity for all optical load and switching. Moreover, some key technologies for i-SAON are described, including the rapid adjustment and control of the laser beam direction, the deep learning-based multi-path anti-fault routing, the intelligent multi-fault diagnosis and switching selection mechanism, and the artificial intelligence-based spectrum sensing and situational forecasting.

Energy‑efcient integrated silicon optical phased array

An optical phased array(OPA)is a promising non-mechanical technique for beam steering in solid-state light detection and ranging systems.The performance of the OPA largely depends on the phase shifter,which afects power consumption,insertion loss,modulation speed,and footprint.However,for a thermo-optic phase shifter,achieving good performance in all aspects is challenging due to trade-ofs among these aspects.In this work,we propose and demonstrate two types of energy-efcient optical phase shifters that overcome these trade-ofs and achieve a well-balanced performance in all aspects.Additionally,the proposed round-spiral phase shifter is robust in fabrication and fully compatible with deep ultraviolet(DUV)processes,making it an ideal building block for large-scale photonic integrated circuits(PICs).Using the high-performance phase shifter,we propose a periodic OPA with low power consumption,whose maximum electric power consumption within the feld of view is only 0.33 W.Moreover,we designed Gaussian power distribution in both the azimuthal(ψ)and polar(θ)directions and experimentally achieved a large sidelobe suppression ratio of 15.1 and 25 dB,respectively.

Fast and deterministic optical phased array calibration via pointwise optimisation

Owing to the structural errors in the optical phased array,an initial random phase reduces the quality of the deflection beam.The most commonly applied approach to phase calibration is based on adaptive optics.However,adaptive optimisation approaches have slow convergence and low diffraction efficiency.We proposed a pointwise optimisation approach to achieve fast and accurate beam deflection.This approach conducts phase calibration,combining global traversal and local searches individually for each array element.We built a phase-calibration optical system containing a one-dimensional optical waveguide phase array for further verification and designed the relevant mechanics.The simulation and experimental results demonstrate that the pointwise optimisation approach accelerates the calibration process and improves the diffraction efficiency.

Photonic microwave true time delays for phased array antennas using a 49 GHz FSR integrated optical micro-comb source[Invited]

We demonstrate significantly improved performance of a microwave true time delay line based on an integrated optical frequency comb source. The broadband micro-comb(over 100 nm wide) features a record low free spectral range(FSR) of 49 GHz, resulting in an unprecedented record high channel number(81 over the C band)—the highest number of channels for an integrated comb source used for microwave signal processing. We theoretically analyze the performance of a phased array antenna and show that this large channel count results in a high angular resolution and wide beam-steering tunable range. This demonstrates the feasibility of our approach as a competitive solution toward implementing integrated photonic true time delays in radar and communications systems.

Optical true time-delay for two-dimensional phased array antennas using compact fiber grating prism

A two-dimensional(2D) optical true-time delay(TTD) beam-forming system using a compact fiber grating prism(FGP) for a planar phased array antenna(PAA) is proposed. The optical beam-forming system mainly consists of a TTD unit based on the same compact FGP, one tunable laser for elevation beam steering, and a controlled wavelength converter for azimuth beam steering. A planar PAA using such 2D optical TTD unit has advantages such as compactness, low bandwidth requirement for tunable laser sources, and potential for large-scale system implementations. The proof-of-concept experiment results demonstrate the feasibility of the proposed scheme.

Smith–Purcell radiation-like photoacoustic phased array

Relativistic electrons moving over a periodic metal grating can lead to an intriguing emission of light,known as Smith–Purcell radiation[SPR],the precursor of the free-electron laser.The speed of light plays a critical role in the far-field emission spectrum.Inspired by this photonic SPR,here we experimentally demonstrate a photoacoustic phased array using laser-induced shock waves.We observe acoustic radiation spectrum in the far field,perfectly predicted by a universal theory for the SPR.This scheme provides a tool to control the acoustic radiation in the near field,paving the way toward coherent acoustic wave generation and microstructure metrology.

10 Gb/s free space optical interconnect with broadcasting capability enabled by a silicon integrated optical phased array

We have proposed and experimentally demonstrated a reconfigurable free space optical interconnect with broadcasting capability based on an eight-channel silicon integrated optical phased array.By using the silicon integrated beam steering and broadcasting device,10 Gb/s on-off keying data is transmitted over 15 cm in free space for up to three receivers located in three different cards.The experimental results show that the optical phased array can be used with broadcasting capability provided to multi-receivers in the card to card optical interconnects,which can significantly reduce device size,system complexity,and total costs.

Optical True Time Delay for Phased Array Antennas Composed of 2×2 Optical MEMS Switches and Fiber Delay Lines

We proposed an optical true time delay (TTD) for phased array antennas (PAAs) composed of 2×2 optical MEMS switches, single-mode fiber delay lines, and a fixed wavelength laser diode. A 3-bit TTD for 10 GHz PAAs was implemented with a time delay error less than ± 0.2 ps.

Fabrication, Characterization and Optical Properties of TiO2 Nanotube Arrays on Boron-doped Diamond Film Through Liquid Phase Deposition

TiO2 nanotube（TiNT） arrays were deposited on boron-doped diamond films by a liquid-phase deposition method with ZnO nanorod arrays as the template.The different morphologies of TiNTs have been obtained by controlling the morphology of ZnO template.The X-ray diffraction and energy-dispersive X-ray analysis show that the ZnO nanorod array template has been removed in the TiNTs formation process.The crystalline quality of the TiNTs is improved by increasing the annealing temperature.The band gap of the TiNTs is about 3.25 eV estimated by the UV-Vis absorption spectroscopy,which is close to the value of bulk TiO2.In the photoluminescence spectrum,a broad visible emission in a range of ca.550-750 nm appears due to the surface oxygen vacancies and defects.

Optically controlled phase array antenna [Invited]

To overcome the beam squint in wide instantaneous frequency, we review a number of system-level optical controlled phase array antennas for beam forming. The optical delay network based on a fiber device in terms of topological structure of an N-bit optical switch, fiber grating, high-dispersion fiber, and vector-sum technology is discussed, respectively. Lastly, an integrated circuit is simply summarized.

Optimized optical design of thin-film transistor arrays for high transmittance and excellent chromaticity

Transmittance and chromaticity are essential requirements for optical performance of thin-film transistor(TFT)arrays.However,it is still a challenge to get high transmittance and excellent chromaticity at the same time.In this paper,optimized optical design by using antireflection film theory and optical phase modulation is demonstrated in low temperature poly-silicon(LTPS)TFT arrays.To realize high transmittance,the refractive index difference of adjacent films is modified by using silicon oxynitride(SiOxNy)with adjustable refractive index.To realize excellent chromaticity,the thicknesses of multilayer films are precisely regulated for antireflection of certain wavelength light.The results show that the transmittance and chromaticity have been improved by about 6%and 18‰,respectively,at the same time,which is a big step forward for high optical performance of TFT arrays.The device characteristics of the TFT arrays with the optimal design,such as threshold voltage and electron mobility,are comparable to those of conventional TFT arrays.The optimized optical design results in enhanced power-conversion efficiencies and perfects the multilayer film design on the basic theory,which has great practicability to be applied in TFT arrays.

Discovery of the low temperature phase barium metaborate (BBO) and its significance in the search for new type nonlinear optical materials

1 History of discovery of the low temperature phase barium metaborate （BBO）——an excel-lent new-type ultraviolet radiation frequency-doubling crystalline materialTHE first laser excitation in 1960 with ruby （α-Al2O3: Cr） as a laser crystal and the first dou-bling of frequency （347. 15 nm） in 1961 by irradiating quartz crystal （α-SiO2） with a 694. 3nm laser beam have laid the basis for the study of laser and nonlinear optical （NLO） crystals,

Silicon photonics for telecom and data‐com applications

In recent decades,silicon photonics has attracted much attention in telecom and data-com areas.Constituted of high refractive-index contrast waveguides on silicon-on-insulator(SOI),a variety of integrated photonic passive and active devices have been implemented supported by excellent optical properties of silicon in the mid-infrared spectrum.The main advantage of the silicon photonics is the ability to use complementary metal oxide semiconductor(CMOS)process-compatible fabrication technologies,resulting in high-volume production at low cost.On the other hand,explosively growing traffic in the telecom,data center and high-performance computer demands the data flow to have high speed,wide bandwidth,low cost,and high energy-efficiency,as well as the photonics and electronics to be integrated for ultra-fast data transfer in networks.In practical applications,silicon photonics started with optical interconnect transceivers in the data-com first,and has been now extended to innovative applications such as multi-port optical switches in the telecom network node and integrated optical phased arrays(OPAs)in light detection and ranging(LiDAR).This paper overviews the progresses of silicon photonics from four points reflecting the recent advances mentioned above.CMOS-based silicon photonic platform technologies,applications to optical transceiver in the data-com network,applications to multi-port optical switches in the telecom network and applications to OPA in LiDAR system.

Fourier domain optical coherence tomography with ultralong depth range

The depth ranges of typical implementations of Fourier domain optical coherence tomography （FDOCT）, including spectral domain OCT （SDOCT） and swept source OCT （SSOCT）, are limited to several millimeters. To extend the depth range of current OCT systems, two novel systems with ultralong depth range were developed in this study. One is the orthogonal dispersive SDOCT （OD-SDOCT）, and the other is the recirculated swept source （R-SS） interferometer/OCT. No compromise between depth range and depth resolution is required in both systems. The developed OD-SDOCT system realized the longest depth range （over 100 mm） ever achieved by SDOCT, which is ready to be modified for depth-encoded parallel imaging on multiple sites. The developed R-SS interferometer achieved submicron precision within a depth range of 30mm, holding potential in real-time contact-free on-axis metrology of complex optical sys- tems.