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.

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).

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.

一维硅基OPA光相位调控性能测试系统

为实现光学相控阵(OPA:Optical Phased Array)的光相位调控性能的快速测试,即快速测试OPA波束扫描角度对应的配置电压,设计了一个具有自反馈功能的闭环测试系统。由上位机控制64路驱动电源为OPA提供配置电压,通过远红外相机检测OPA出射光在成像屏上的光场分布,根据主瓣位置确定的波束扫描角度,以余弦相似度为指标与预置的扫描角度进行对比,进一步调整OPA的各路配置电压,最后得到设定的波束扫描角度对应的最佳实际配置电压。实验证明,该系统可以在16 min内实现OPA指定波束扫描角度对应的64路配置电压的快速测试,所得峰值旁瓣电平为-10 d B左右,且系统具有高稳定性,强抗干扰能力和快速测试等优点。

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.

Polarization-independent two-dimensional beam steering using liquid crystal optical phased arrays

A polarization-independent nonmechanical laser beam steering scheme is proposed to realize continuous two-dimensional（2 D） scanning with high efficiency, where the core components are two polarization-dependent devices, which are called liquid crystal optical phased arrays（LC-OPAs）. These two one-dimensional（1D） devices are orthogonally cascaded to work on the state of azimuthal and elevation steering, respectively. Properties of polarization independence as well as 2D beam steering are mathematically and experimentally verified with a good agreement. Based on the experimental setup, linearly polarized beams with different polarization angles are steered with high accuracy. The measured angular deviations are less than 5 μrad, which is on the same order of the accuracy of the measurement system. This polarization-independent 2 D laser beam steering scheme has potential application for nonmechanical laser communication, lidar, and other LC-based systems.

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.

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.

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.

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.

超短中红外参量放大过程的时空走离特性

计算了MgO:LiNbO3晶体中,共线与非共线相位匹配光参量放大产生超短中红外激光脉冲过程中的相位匹配曲线、有效非线性系数以及时间和空间走离情况。结果表明,采用非共线相位匹配方式,可以实现三波间群速度匹配;在抑制了泵浦光与信号光之间的空间走离的同时加大了泵浦光与闲频光之间的空间走离,但这种影响可以忽略;同时非共线角的引入使相位匹配角增大,提高了有效非线性系数。因此,非共线角的引入在不影响空间走离的情况下,有效补偿超短中红外参量放大过程中的时间走离,有利于参量放大转换效率的提高。

基于光纤光参量放大的光脉冲压窄技术的研究

在高重复频率的光窄脉冲源中,为了获得更窄的脉冲,需要增加泵浦功率;但泵浦功率的提高会使光放大器的增益趋于饱和,放大的自发辐射噪音增强,脉冲光信噪比下降.为此,提出了利用啁啾管理和光纤光参量放大相结合的脉冲压窄方案.将强度调制后的泵浦光通过相位调制引入线性负啁啾,由于经参量过程后在新的闲频光上啁啾会加倍,从而进一步增大了信号的谱宽,并通过色散补偿介质实现了光脉冲压缩.实验给出了10GHz速率下的结果,通过泵浦光的相位调制在0.5W平均泵浦光功率条件下得到了脉宽19ps的光脉冲,结果与理论分析基本吻合.

光子晶体光纤在1.4μm处光谱展宽的实验研究

采用输出波长为1.4 μm的光参量放大器(OPA)作为泵浦源,泵浦0.2m长的光子晶体光纤,观察到光谱展宽现象.实验得到的光谱宽度达58.4nm(1.3708～1.4292μm ),比OPA输出的光谱宽度(30.4nm)展宽28nm.

光学相控阵相位驱动电路的设计与实现

为了驱动光学相控阵(OPA:Optical Phased Array)实现全固态激光雷达的光束扫描,设计并实现了两种用于OPA相位控制的驱动电路,其中包括电流源驱动和电压源驱动两种驱动电路。采用PC(Phase Control)端的上位机软件控制连接到电流源或电压源的单片机,对OPA各路相位控制端的电流或电压进行调节,改变OPA远场光束主极大的位置,从而达到光束偏转的目的,实现光束扫描。分析了多通道、高功率、高精度、宽范围的电流源和电压源的驱动原理,完成了系统的软硬件设计与实现。最后进行了误差与线性度测试和OPA相位控制实验,结果证明了该驱动电路的可行性与正确性。提出的两种OPA相位控制电路原理简单、稳定性强、方便实用,在高精度OPA相位控制方面具有一定的应用价值。

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.