Optical Phased Array Technology Research Articles

Optical phased array output beam calibration method based on Adam algorithm

<sec>Optical phased array (OPA) technology, as a pivotal component of laser detection and ranging (LiDAR) systems, plays a crucial role in augmenting the application efficiency in fields such as autonomous driving, precision measurement, and remote sensing detection. With the escalating demands for high-resolution imaging, the array size of OPAs is continuously expanding, imposing higher requirements on the calibration precision and efficiency of the output beam. Existing calibration algorithms, such as the simultaneous perturbation stochastic gradient descent (SPGD) and the Gerchberg-Saxton (GS) algorithm, often face challenges of prolonging calibration times and insufficient precision when dealing with large-scale OPA systems.</sec><sec>In order to address this problem, our study introduces the Adam optimization algorithm, renowned for its adaptive learning rate feature, into the calibration process of OPA output beams. Through simulation modeling and experimental validation, this work comprehensively examines the differences in performance between the Adam algorithm and conventional SPGD and GS algorithms in beam calibration, especially under various OPA array configurations. For a 16×16 OPA array, the application of the Adam algorithm significantly enhances the peak side lobe ratio (PSLR) to over 15.98 dB, while notably reducing the number of iterations to less than 600, thereby shortening the calibration cycle and improving calibration precision effectively.</sec><sec>Furthermore, this work provides an in-depth analysis of parameter selection, convergence speed, and stability of the Adam algorithm in OPA calibration, offering detailed guidance for achieving more efficient and high-quality beam calibration. Through comparative analysis, this work not only demonstrates the substantial advantages of the Adam algorithm in enhancing OPA calibration efficiency, reducing calibration duration, and optimizing output beam quality but also emphasizes its critical role in advancing OPA technology.</sec><sec>The main contribution of this work lies in providing an innovative algorithmic approach for achieving efficient calibration of OPA output beams, which has important theoretical and practical significance for advancing the LiDAR technology, particularly in the field of high-precision beam control. Moreover, by applying optimized algorithms, this study not only improves the performance of OPA technology within existing domains but also paves new ways for its application in emerging fields such as optical communication, optical networking, and high-resolution imaging.</sec>

Outlook on Development of Laser Communication from Perspective of Optical Phased Array Technology (Invited)

Outlook on Development of Laser Communication from Perspective of Optical Phased Array Technology (Invited)

Research Progress on Liquid Crystal Optical Phased Array Technology for Laser Communication (Invited)

Research Progress on Liquid Crystal Optical Phased Array Technology for Laser Communication (Invited)

Design of high-efficiency and large-field silicon-based transceiver integrated optical phased array

With the rapid development of photonic integrated circuits, optical phased array (OPA) technology has attracted much attention in recent years because it can turn quickly without mechanical structure, and has been widely studied in the fields of light detection and ranging (LiDAR). However, the two-dimensional optical phased array antenna is still limited by the antenna spacing, and it is difficult to expand the scanning range. We propose a two-dimensional silicon-based optical phased array (OPA) transceiver with high efficiency and a large field of view. The structure adjusts the phase of the two dimensions of the antenna through the external waveguide phase shifter of the antenna array and further scans the two dimensions of the far field. We take an 8 × 8 array as an example, reasonably design the array structure, and optimize the performance of some functional devices. Finally, the scanning range of 14.9°×11.2° can be achieved. At the same time, we can realize the free switching of the OPA receiving and transmitting functions through an optical switch.

High-directionality SiN-assisted grating antenna for optical phased array

In the realm of consumer electronics, automotive, and robotics, lidar has proven to be a valuable technology. However, current lidar solutions such as mechanical, microelectromechanical, and flash lidar are associated with drawbacks such as high cost, low resolution, and a limited ranging distance. To address these issues, optical phased array (OPA) technology has been proposed as a promising solution due to its high resolution, rapid response times, long ranging distance, and low cost. Despite these advantages, OPA is still in the developmental stages and further optimization is required to address issues such as loss, field of view (FOV), and beam divergence. To address the FOV and beam divergence issues, SiN-assisted grating antenna has been used. However, the directionality of an SiN-assisted antenna is relatively low and may introduce additional loss for OPA. To overcome this limitation, this paper proposes a dual-layer SiN-assisted grating antenna with more than 94% directionality in 1550 nm. Moreover, the wavelength bandwidth of more than 90% directionality is over 80 nm, making it a promising solution for OPA devices.

Research of Non-mechanical Beam Scanning Technology

Laser beam scanning technology has been widely used in various fields such as LIDAR, photoelectric detection and space optical communication, etc. Mechanical scanning has problems such as inflexibility and low scanning rate. This paper introduces the basic principles of acoustic-optical scanning, electro-optical scanning, optical phased array and MEMS scanning, and analyses the advantages and disadvantages of several scanning methods and the main application scenarios, and finds that the current optical scanning technology is developing towards large scanning angle, high accuracy, fast response and miniaturization, among which the liquid crystal optical phased array and MEMS scanning technology are relatively mature. The scanning angle of the LCD optical phased array can reach ±10°, and the scanning angle of the MEMS can reach 6.6°*4.4°, which has a broad development prospect.

All-Solid-State Beam Steering via Integrated Optical Phased Array Technology.

Light detection and ranging (LiDAR), combining traditional radar technology with modern laser technology, has much potential for applications in navigation, mapping, and so on. Benefiting from the superior performance, an all-solid-state beam steering realized by integrated optical phased array (OPA) is one of the key components in the LiDAR system. In this review, we first introduce the basic principle of OPA for beam steering. Then, we briefly review the detailed advances of different solutions such as micro-electromechanical system OPA, liquid crystal OPA, and metasurface OPA, where our main focus was on the recent progress of OPA in photonic integrated chips. Finally, we summarize the different solutions and discuss the challenges and perspectives of all-solid-state beam steering for LiDAR.

Wide-steering-angle high-resolution optical phased array

Optical phased array (OPA) technology is considered a promising solution for solid-state beam steering to supersede the traditional mechanical beam steering. As a key component of the LIDAR system for long-range detection, OPAs featuring a wide steering angle and high resolution without beam aliasing are highly desired. However, a wide steering range requires a waveguide pitch less than half of the wavelength, which is easily subjected to cross talk. Besides, high resolution requires a large aperture, and it is normally achieved by a high count number of waveguides, which complicates the control system. To solve the mentioned issues, we design two high-performance 128-channel OPAs fabricated on a multilayered SiN-on-SOI platform. Attributed to the nonuniform antenna pitch, only 128 waveguides are used to achieve a 4 mm wide aperture. Besides, by virtue of innovative dual-level silicon nitride ( Si 3 N 4 ) waveguide grating antennas, the fishbone antenna OPA achieves a 100 ° × 19.4 ° field of view (FOV) with divergence of 0.021 ° × 0.029 ° , and the chain antenna OPA realizes a 140 ° × 19.23 ° FOV with divergence of 0.021 ° × 0.1 ° . To our best knowledge, 140° is the widest lateral steering range in two-dimensional OPA, and 0.029° is the smallest longitudinal divergence. Finally, we embed the OPA into a frequency-modulated continuous-wave system to achieve 100 m distance measurement. The reflected signal from 100 m distance is well detected with 26 dBm input transmitter power, which proves that OPA serves as a promising candidate for transceiving optical signal in a LIDAR system.

Conventional surface micromachining process for the fabrication of a linear optical phased array based on piston micromirrors

Micro electromechanical system (MEMS) based optical phased array (OPA) technology generally demands narrow and tightly spaced suspended microstructures with high-aspect-ratio in the lateral dimensions. This paper presents an one dimensional OPA system which is fabricated using the standard PolyMUMPs process, leading to a low-cost, simplified and commercially accessible surface micromachining technique for the OPA technology. The proposed OPA device utilizes an array of metal-coated silicon micromirrors with high-aspect-ratio structures which act as optical phase shifters. Each micromirror along the array is individually actuated by an electrostatic parallel plate micro-actuator made of a micro-cantilever beam positioned above a fixed electrode. The field of view obtained by the device is measured as 4.76° which is comparable to those by the previous MEMS based OPA devices fabricated using custom-run and complex surface micromachining processes. The OPA device has a response time of 6.5 µs and an out of plane actuation stroke of 0.16 µm at a bias voltage of 55 V. The magnitude of the out of plane displacement by the phase shifters is equal to one-quarter of the laser wavelength (650 nm) used which leads to the desired optical phase shift of radian.

On the performance of optical phased array technology for beam steering: effect of pixel limitations.

Optical phased arrays are of strong interest for beam steering in telecom and LIDAR applications. A phased array ideally requires that the field produced by each element in the array (a pixel) is fully controllable in phase and amplitude (ideally constant). This is needed to realize a phase gradient along a direction in the array, and thus beam steering in that direction. In practice, grating lobes appear if the pixel size is not sub-wavelength, which is an issue for many optical technologies. Furthermore, the phase performance of an optical pixel may not span the required 2π phase range or may not produce a constant amplitude over its phase range. These limitations result in imperfections in the phase gradient, which in turn introduce undesirable secondary lobes. We discuss the effects of non-ideal pixels on beam formation, in a general and technology-agnostic manner. By examining the strength of secondary lobes with respect to the main lobe, we quantify beam steering quality and make recommendations on the pixel performance required for beam steering within prescribed specifications. By applying appropriate compensation strategies, we show that it is possible to realize high-quality beam steering even when the pixel performance is non-ideal, with intensity of the secondary lobes two orders of magnitude smaller than the main lobe.

光学相控阵技术研究进展

光学相控阵技术研究进展

Optical multi-beam forming method based on a liquid crystal optical phased array

Three multi-beam forming methods based on optical phased array technology are presented in this paper. These methods can achieve simultaneous multiple-beam pointing in the optical band. The principles of these methods are introduced, the far-field pattern calculation formulas of the subaperture method and the array division multiplexing method are derived, and the algorithm flow of the iterative Fourier transform method is described in detail. Simulations and experiments have been conducted to verify the validity of these methods.

Two-dimensional beam steering using a thermo-optic silicon photonic optical phased array

Many components for free-space optical (FSO) communication systems have shrunken in size over the last decade. However, the steering systems have remained large and power hungry. Nonmechanical beam steering offers a path to reducing the size of these systems. Optical phased arrays can allow integrated beam steering elements. One of the most important aspects of an optical phased array technology is its scalability to a large number of elements. Silicon photonics can potentially offer this scalability using CMOS foundry techniques. A phased array that can steer in two dimensions using the thermo-optic effect is demonstrated. No wavelength tuning of the input laser is needed and the design allows a simple control system with only two inputs. A benchtop FSO link with the phased array in both transmit and receive mode is demonstrated.

Improvement for the steering performance of liquid crystal phased array

Optical phased array technology is introduced and the steering performances of liquid crystal phased array are discussed, several factors affecting the beam steering performances are analyzed completely, also simple models for some typical factors are developed. Then, a new method based on iterating and modifying the output phase pattern of liquid crystal phase shifters is proposed. Using this method, the modified voltages applied on electrodes of liquid crystal phase shifters can be obtained, after applying the voltages, the influence of factors can be compensated to some extent; the steering angle accuracy and efficiency with liquid crystal phased array can be improved. Through the simulation for the angle range from 0° to −1°, the error of steering angle can be reduced three orders of magnitude, and the efficiency can be increased almost 30% after several iterations.

基于电光材料的光学相控阵技术研究进展

基于电光材料的光学相控阵技术研究进展

Experimental investigation of optical beam deflection based on PLZT electro-optic ceramic

Based on the optical characteristics of PLZT (Lead Lanthanum Zirconate Titanate) electro-optic ceramic, two kinds of electro-optical deflectors, triangular electrode structure and optical phased array technology, are studied in detail by using transverse electro-optic effect. Theoretically, the electro-optic deflection characteristics and mechanisms of the deflectors are analyzed; experimentally, the optical characteristics of ceramic wafer, such as the phase modulation, the hysteresis and the electro-induced loss characteristics, are measured; a systematic experiment is designed to verify the theoretical results. The effect of temperature on the performance of deflector is also investigated. Comparing with both structure's deflectors, the optical phased array technology has a higher angle scanning resolution, however, it has a relative small deflection angle. OCIS codes: (230.2090) Electro-optical devices; (160.2100) Electro-optical materials; (060.5060) Phase modulation.

Ultra-fast speed, low grating lobe optical beam steering using unequally spaced phased array technique

In this paper, we present a low grating lobe optical beam steering technique using an unequally spaced phased array, in which the required spacings among the phase elements are quantitatively analyzed so that the grating lobe can be minimized by destructive interference. A large grating lobe is one of the major drawbacks of optical phased array technology because it limits the light efficiency and the quality of the light beam. Thus, the low grating lobe technique presented in this paper could substantially improve the light efficiency and the quality of light beam, and could potentially be used in a variety of applications such as fast speed ladar beam steering, large size high resolution displays, and wide bandwidth free space optics communications.

Phased Array of Phased Arrays (PAPA) Laser Systems Architecture

This paper introduces and analyzes revolutionary laser system architecture capable of dramatically reducing the complexity of laser systems while simultaneously increasing capability. The architecture includes three major subsystems. The first is a phased array of laser sources. In this article, we discuss diode-pumped fiber lasers as the elements of the phased array, although other waveguide lasers can also be considered. The second provides wavefront control and electronics beam steering, as described in an IEEE Proceedings article on “Optical Phased Array Technology” [1]. The third is subaperture receiver technology. Combining these three technologies into a new laser systems architecture results in a system that has graceful degradation, can steer to as wide an angle as individual optical phased array subapertures, and can be scaled to high power and large apertures through phasing of a number of subapertures.Diode-pumped fiber lasers are appealing as laser sources because they are electrically pumped, efficient, relatively simple, and scalable to significant power levels (over 100 Watts has been demonstrated from a single diode-pumped fiber laser) [2]. The fiber laser design also lends itself to integration into a phased array. Fiber lasers have been phased. Initial phasing demonstrations have been at low power and were conducted by taking a single source, dividing it into multiple fibers, then phasing them together. To develop this technology further we need to use independent fiber lasers or fiber amplifiers, seeded by a common source, and to increase laser power. As we increase laser power, we will have to learn to cope with nonlinearities in the laser amplifiers.Optical Phased Array technology has demonstrated steering over a 90-degree field of regard [4], although this approach used additional optical components. If we use straightforward optical phased array beam steering without additional optics we can steer with high efficiency to about one-third λ/d, where d is the smallest individually addressable element. The one-third factor depends on the efficiency threshold. For example, if we use 1.5 μm light, and 5 μm center-to-center spacing, we can steer with high efficiency to about ±6 degrees, or a field of regard of 12 degrees.Last, we need to develop a subaperture receive technology. This can be a pupil plane receiver, an image plane receiver, or some combination of the approaches. When we have matured each individual technology and combined them into new laser systems architectures, we will have the ability to build simpler and more capable laser systems. The vision for an integrated, phased array laser concept is to enable a new class of laser systems with significant advantages, including high-efficiency, all-electric laser source; all waveguide beam transport; wavefront control at the sub-aperture level (enabling wavefront compensation, conformal apertures, and wide-angle electronic beam steering); random access beam pointing over wide angles; multiple simultaneous beam generation and control; and graceful degradation.

Optical phased array technology

Optical phased arrays represent an enabling new technology that makes possible simple affordable, lightweight, optical sensors offering very precise stabilization, random-access pointing programmable multiple simultaneous beams, a dynamic focus/defocus capability, and moderate to excellent optical power handling capability. These new arrays steer or otherwise operate on an already formed beam. A phase profile is imposed on an optical beam as it is either transmitted through or reflected from the phase shifter array. The imposed phase profile steers, focuses, fans out, or corrects phase aberrations on the beam. The array of optical phase shifters is realized through lithographic patterning of an electrical addressing network on the superstrate of a liquid crystal waveplate. Refractive index changes sufficiently large to realize full-wave differential phase shifts can be effected using low (<10 V) voltages applied to the liquid crystal phase plate electrodes. High efficiency large-angle steering with phased arrays requires phase shifter spacing on the order of a wavelength or less; consequently addressing issues make 1-D optical arrays much more practical than 2-D arrays. Orthogonal oriented 1-D phased arrays are used to deflect a beam in both dimensions. Optical phased arrays with apertures on the order of 4 cm by 4 cm have been fabricated for steering green, red, 1.06 /spl mu/m, and 10.6 /spl mu/m radiation. System concepts that include a passive acquisition sensor as well as a laser radar are presented.