Optical Phased Array Research Articles

Precise beam control in optical phased arrays using the four steps rotating element electric field vector method

The integrated optical phase arrays (OPAs) possess the capability for rapid modulation and precise control of output beam deflection, making it widely applicable in fields such as three-dimensional terrain reconstruction, autonomous driving, and holographic imaging. However, the unknown initial phase introduced during the manufacturing and packaging processes of current OPAs results in low beam alignment quality and random output beam phases, significantly limiting the development and application of OPAs. To address these challenges, this paper proposes a precise control technology for OPA output beams, utilizing a beam calibration method we have developed, known as the Four Steps Rotating Element Electric Field Vector Method. This method enables rapid and accurate calibration, achieving precise phase control for each antenna on the OPA chip by calibrating the phase shift and controlling the voltage relationship. It overcomes the challenges of unknown phase distributions common in passive calibration methods, aligning the calibrated phase distribution more closely with theoretical expectations. The proposed method further enhances control over the OPA output beam. Based on this technology, we constructed an experimental platform to achieve a main lobe with a PSLR of 15.98 dB and successfully generated vortex beams using a 4×4 OPA. This innovation not only addresses the initial phase issues caused by manufacturing errors but also significantly enhances the precise control of OPA phases, expanding its applications in LiDAR systems.

Two dimensional integrated optical phased array with high fill-factor antennas

Two dimensional integrated optical phased array with high fill-factor antennas

Three-wavelengths integrated SiN optical phased array for LiDAR and FSO data link applications

We propose a scalable integrated silicon nitride optical phased array (OPA) enabling multi-beam emission and two-dimensional continuous beam steering for light detection and ranging (LiDAR), free-space optics (FSO), and data link applications. The emitters are optimized grating couplers for wavelengths of 800 nm, 850 nm, and 905 nm. We propose three OPAs, two with 8 emitters and one with 16 emitters. The OPAs are characterized at a wavelength of 850nm. The measured beam size of the OPAs are 0.96° ×0.12°, 0.69° ×5.42°, and 0.7° ×1.53°. A lateral beam steering of ±12.35° is measured. The proposed configuration of the thermo-optical phase shifters along the OPA tree provides a simple multi-level beam splitting resolution for each OPA. By enhancing the unwanted side lobes, a discrete angular selection resolution is achieved, improving from 6.1° to 0.082°. We proposed an array of heaters to suppress the unwanted side lobes of the radiation pattern, and its performance is measured and presented. We measured the modulated beam considering pulses with different duty cycles up to 5 MHz and data rates up to 6.25 Mb/s.

Vertical directional coupling based grating emission engineering for optical phased arrays: publisher’s note

Vertical directional coupling based grating emission engineering for optical phased arrays: publisher’s note

Half-wavelength-pitch silicon optical phased array with a 180° field of view, high sidelobe suppression ratio, and complex-pattern beamforming

Solid-state optical beam steering devices desire a large field of view (FOV), good beam quality, and reconfigurable beamforming of complex patterns, which are not available in a single system yet. Having not been demonstrated, an active beamformer using an optical phased array (OPA) could potentially fulfill these requirements simultaneously, because it can control both the wavefront and beam pattern. Half-wavelength-pitch OPAs theoretically can achieve the three requirements concurrently, but suffer from crosstalk. Most previous efforts focus on mitigating/avoiding crosstalk. Instead, here we appreciate its existence and propose/demonstrate a programmable architecture to compensate for it. Using a tree of composite variable splitters with a full splitting-ratio range, we achieve arbitrary amplitude/phase modulation to pre-correct scrambled phase/amplitude by crosstalk. With comprehensive stray-light minimization strategies, the sidelobe suppression ratio (SLSR) is significantly improved. Our design achieves a 180∘ FOV, a peak SLSR of 24 dB, and complex-pattern beamforming simultaneously in a half-wavelength-pitch 64-waveguide array. Within the ±60∘ range, a SLSR of >20dB is achieved. Our OPA demonstrates Bayliss difference, pulse-shaped, and asymmetric three-beam patterns with high SLSRs of >20dB, ∼10dB, and >18dB, respectively. These performance metrics are important for various applications in light detection and ranging, imaging, and communication.

Mid-infrared 2D nonredundant optical phased array of mirror emitters in an InGaAs/InP platform

The extension of photonic technologies such as lidar and free-space optical communications from the traditional visible and near-infrared wavelengths to longer wavelengths can improve performance in adverse environments such as haze, fog, smoke, or strong solar background. Non-mechanical beam steerers will be a critical component of the low size, weight, and power modules needed for the portable or unmanned systems deployed in these environments. In this work, we demonstrate the first 2D optical phased array for non-mechanical beam steering in the mid-infrared spectral region. We combine a total-internal-reflection mirror emitter with a nonredundant array of 30 elements to carry out 2D beam steering at a single wavelength of 4.6 µm. The experiment yielded ∼600 resolvable far-field points, with ∼2400 points over a 28° × 28° field of view calculated theoretically. Moreover, the device was fabricated in a passive InGaAs/InP platform, contributing another advance in the ongoing development of quantum cascade laser-based photonic integration.

Optical beam steering and distance measurement experiments through an optical phased array

Optical beam steering and distance measurement experiments through an optical phased array

Two dimensional beam forming and steering based on silicon nitride 1 × 32 optical phased array

Two dimensional beam forming and steering based on silicon nitride 1 × 32 optical phased array

Emitter design for efficient waveguide spectral lens

Abstract As an alternative to arrayed waveguide gratings (AWGs), the waveguide spectral lens (WSL) stands out with the ability to focus light in free space, thereby eliminating the need for relay optics between the chip and the camera. This becomes convenient in constructing a truly compact instrument for astronomical spectroscopic analysis. Besides dispersion and focusing, WSL offers another important function: the envelope of the diffraction orders can be manipulated via the output emitter, i.e., the waveguide array at the facet. Through careful emitter design, the diffraction efficiency can be largely improved because the side orders are well suppressed, and light is concentrated to the selected order. This feature, though particularly important for the photon-hungry astronomical application, has not been well explored in the previous works. Here, we come up with four emitter designs and evaluate their performance, including linear taper, parabolic taper, multimode interference (MMI), and slot MMI. A figure of merit (FoM) considering both diffraction efficiency and uniformity is introduced to identify the optimal structure. Experimental results agree well with the simulation and confirmed that the optimal parabolic taper can achieve a diffraction efficiency of 90.9%, making it the most attractive design. This work highlights the potential of WSLs for astronomical spectroscopy with an efficiency that rivals conventional blazed gratings. It may also inspire emitter designs for side-lobe suppression in optical phase array applications.

Visible-Light Uniform and Unidirectional Grating-Based Antennas for Integrated Optical Phased Arrays

Visible-Light Uniform and Unidirectional Grating-Based Antennas for Integrated Optical Phased Arrays

Inverse-Designed Ultra-Compact Passive Phase Shifters for High-Performance Beam Steering.

Ultra-compact passive phase shifters are inversely designed by the multi-objective particle swarm optimization algorithm. The wavelength-dependent phase difference between two output beams originates from the different distances of the input light passing through the 4 μm × 3.2 μm rectangular waveguide with random-distributed air-hole arrays. As the wavelength changes from 1535 to 1565 nm, a phase difference tuning range of 6.26 rad and 6.95 rad is obtained for TE and TM modes, respectively. Compared with the array waveguide grating counterpart, the phase shifters exhibit higher transmission with a much smaller footprint. By combining the inverse-designed phase shifter and random-grating emitter together, integrated beam-steering structures are built, which show a large scanning range of ±25.47° and ±27.85° in the lateral direction for TE and TM mode, respectively. This work may pave the way for the development of ultra-compact high-performance optical phased array LiDARs.

Phase-locked high-brightness interband cascade laser array with multimode interferometer couplers.

We report on the design, fabrication, and characterization of an interband cascade laser (ICL) array incorporating multimode interference (MMI) couplers for phase-locking emitters. The ICL array, emitting at 3-4 µm, was developed to address the challenges of heat dissipation and in-phase operation in mid-infrared lasers. The array features a 7.5-µm-wide ridge design for fundamental transverse mode propagation and employs MMI structures to realize an in-phase operation of multiple emitters. The far-field patterns, characterized by periodic and symmetrical interference fringes, confirm the coherent operation of the array and the efficacy of MMI couplers in achieving phase-locking. The single-ridge side of the array exhibits a single-lobe far-field profile, with higher-order transverse modes effectively suppressed, showcasing a nearly diffraction-limited beam quality (M2 ≈ 1.31) at high output powers (390 mW from the 1 × 4 array). The robust performance and scalable design of the ICL array, validated by experimental results and theoretical simulations, indicate its potential for high-power mid-infrared applications and as an optical phased array.

Silicon Optical Phased Array Hybrid Integrated with III–V Laser for Grating Lobe-Free Beam Steering

Silicon Optical Phased Array Hybrid Integrated with III–V Laser for Grating Lobe-Free Beam Steering

Retraction Note: Advancing chemical sensors synthesis and classification for the integration of mems optical phased array in polymer nanocomposites

Retraction Note: Advancing chemical sensors synthesis and classification for the integration of mems optical phased array in polymer nanocomposites

Retraction Note: Machine learning aided design and optimization of MEMS optical phased array with silicon micro mirrors for nanofabrication

Retraction Note: Machine learning aided design and optimization of MEMS optical phased array with silicon micro mirrors for nanofabrication

Multi-beam solid-state LiDAR using star-coupler-based optical phased arrays.

Solid-state light-detection-and-ranging (LiDAR) sensors based on integrated optical phased arrays (OPAs) have shown significant promise to reduce the cost, size, weight, and power consumption associated with LiDAR for autonomous systems. However, these OPA-based LiDAR systems typically operate by rastering a single beam, generating point clouds that constitute a significant amount of data and computational burden in the process. In this paper, we develop and experimentally demonstrate a novel multi-beam solid-state OPA-based LiDAR system capable of detecting and ranging multiple targets simultaneously, passively, and without rastering. Specifically, we develop the devices, subsystems, and system architectures to realize a solid-state frequency-modulated-continuous-wave (FMCW) LiDAR system that leverages a discrete-Fourier-transform star-coupler-based OPA as a receiver and a multi-beam splitter-tree-based OPA as a transmitter. Using this multi-beam LiDAR system, we demonstrate the simultaneous detection and ranging of two targets at two different cross-range positions without rastering. Through this work, we demonstrate a new spatially-adaptive sensing modality for solid-state LiDAR that enables improved spatial awareness and promises to reduce the data deluge associated with LiDAR in autonomous systems.

Design and analysis of single-electrode integrated lithium niobate optical phased array for two-dimensional beam steering

The realization of high-speed, low-power optical phased array (OPA) on thin-film lithium niobate on insulator (LNOI) is considered an ideal solution for the next generation of solid-state beam steering. Most reported on-chip two-dimensional optical phased arrays suffer from issues such as large antenna spacing, high power consumption and complex wiring due to independent control of array elements. To address these challenges while fully utilizing the benefits of the LNOI platform, we propose a two-dimensional beam-scanning OPA based on lithium niobate (LN) waveguides. We design a multi-layer cascaded domain engineering structure inside the LN waveguide, combined with wavelength tuning, to enable two-dimensional beam scanning with single electrode controlling the OPA. Through simulation, we achieve a 42°×9.2° two-dimensional beam steering. Compared to existing on-chip integrated OPAs, this work offers significant advantages in increasing integration, simplifying control units and reducing power consumption.

Optical tweezing of microparticles and cells using silicon-photonics-based optical phased arrays

Integrated optical tweezers have the potential to enable highly-compact, low-cost, mass-manufactured, and broadly-accessible optical manipulation when compared to standard bulk-optical tweezers. However, integrated demonstrations to date have been fundamentally limited to micron-scale standoff distances and, often, passive trapping functionality, making them incompatible with many existing applications and significantly limiting their utility, especially for biological studies. In this work, we demonstrate optical trapping and tweezing using an integrated OPA for the first time, increasing the standoff distance of integrated optical tweezers by over two orders of magnitude compared to prior demonstrations. First, we demonstrate trapping of polystyrene microspheres 5 mm above the surface of the chip and calibrate the trap force. Next, we show tweezing of polystyrene microspheres in one dimension by non-mechanically steering the trap by varying the input laser wavelength. Finally, we use the OPA tweezers to demonstrate, to the best of our knowledge, the first cell experiments using single-beam integrated optical tweezers, showing controlled deformation of mouse lymphoblast cells. This work introduces a new modality for integrated optical tweezers, significantly expanding their utility and compatibility with existing applications, especially for biological experiments.

Phase-controlled pattern-tunable optical traveling wave antenna array

An optical phased array is designed based on equally spaced identical Au waveguides serving as optical traveling wave antennas (OTWAs). Phased surface plasmon polaritons are fed through the Au waveguides and partly radiate out at the terminals. The simulation results indicate that the pattern maximum of a 7-element OTWA array can be dynamically steered over a range of up to 60.6° by changing the excitation phase differences between the elements, and the main lobe is narrowed compared to the single-element case. A theoretical analysis about the tunable pattern by the pattern multiplication principle is carried out, which is basically consistent with the simulations. Such an OTWA array should have potential applications in nano-optics due to its ability to steer the pattern without mechanical motion.

Dynamic response characteristics of optical beam deflection in liquid crystal optical phased array

The beam deflector based on liquid crystal optical phased array (LCOPA) is a crucial component of space laser communication systems. Understanding and mastering the beam deflection characteristics under the dynamic response of LCOPA is essential for achieving real-time acquisition and tracking in space laser communication. This paper thoroughly explores the beam deflection characteristics during the dynamic response process by analyzing the dynamic response and far-field diffraction models of LCOPA. It presents the far-field diffraction patterns under the dynamic response of LCOPA and validates the analysis through experiments. This study not only enhances the understanding of the dynamic performance of LCOPA but also provides a theoretical basis for its control in space laser communication systems.