Large-scale Optical Phased Array Research Articles

Ultra-Compact and Broadband Nano-Integration Optical Phased Array.

The on-chip nano-integration of large-scale optical phased arrays (OPAs) is a development trend. However, the current scale of integrated OPAs is not large because of the limitations imposed by the lateral dimensions of beam-splitting structures. Here, we propose an ultra-compact and broadband OPA beam-splitting scheme with a nano-inverse design. We employed a staged design to obtain a T-branch with a wavelength bandwidth of 500 nm (1300-1800 nm) and an insertion loss of -0.2 dB. Owing to the high scalability and width-preserving characteristics, the cascaded T-branch configuration can significantly reduce the lateral dimensions of an OPA, offering a potential solution for the on-chip integration of a large-scale OPA. Based on three-dimensional finite-difference time-domain (3D FDTD) simulations, we demonstrated a 1 × 16 OPA beam-splitter structure composed entirely of inverse-designed elements with a lateral dimension of only 27.3 μm. Additionally, based on the constructed grating couplers, we simulated the range of the diffraction angle θ for the OPA, which varied by 0.6°-41.6° within the wavelength range of 1370-1600 nm.

Compact and Low Power-Consumption Solid-State Two-Dimensional Beam Scanner Integrating a Passive Optical Phased Array and Hybrid Wavelength-Tunable Laser Diode

Large-scale optical phased arrays have attracted attention as devices for solid-state beam scanning employing light detection and ranging. However, conventional optical phased arrays using electro-optic phase shifters require active phase control for each antenna. Because the power consumption of the active phase shifters is proportional to the number of antennas, the total power consumption increases in a large-scale optical phased array with a narrow beam divergence. In this study, we propose a passive beam scanner that realizes two-dimensional beam scanning through the wavelength sweep of a laser light. Additionally, most studies on optical phased arrays use external laser diodes as light sources. This increases the size of the beam-scanning system. Therefore, there is a demand for integrating an optical phased array and a laser light source in a combined chip. In this study, we integrated a 64-channel passive optical phased array and a hybrid wavelength-tunable laser diode into a combined chip. The size of the device was 5 mm × 1.5 mm, and the power consumption for beam scanning was 49.3 mW. The field of view was 44.2° × 13.7°, and the full width at half maximum of the beam divergence was 0.517° × 3.67°. Compared with the device used in a previous study, our device was nine times smaller, and the total power consumption was only tens of milliwatts. This device consumes less power and achieves a fully integrated light detection and ranging.

Cascaded Internal Phase Control of All-Fiber Coherent Fiber Laser Array

Fiber lasers have been widely used in medical care, industries, and scientific research in recent years. The coherent beam combining of fiber lasers with an internal phase control has drawn many interests at present, which is a promising method to achieve a large-scale optical phased array. In this article, we presented a cascaded internal phase control method to expand the internal all-fiber phased array. The method distributes the phase measurements to a series of internal Mach–Zender interferometers. Then, the phase of each loop is locked by the gradient descent algorithm. The electric control method to compensate π-ambiguity between channels is proposed. Finally, the phases of the three fiber beams are locked experimentally to verify the feasibility of the method, and the residue phase error is better than λ/22.

Single-Pixel Imaging Using Carrier-Depletion Optical Phased Array With Reduced Phase Shift Requirement

The optical-phased array (OPA) has gained special interest in recent years as a high-speed and compact imaging device. While large-scale OPAs have been demonstrated in single-pixel imaging, the complexity of the driver circuit is becoming a crucial problem as the number of phase shifters increases. Here, we investigate the phase shift requirement of OPA for single-pixel imaging and demonstrate, for the first time, that full 2π phase shifts are not mandatory to generate a set of illumination patterns with a sufficient degree of randomness required to reconstruct the image. Using a silicon photonic OPA chip with 128 carrier-depletion-based phase shifters, we experimentally confirm this property by successfully retrieving an image under a maximum phase shift of only ∼1.5π without affecting the quality of the image. Consequently, the input voltage can be reduced significantly. Since the carrier-depletion phase shifters generally require high driving voltages, this finding paves the way to high-speed OPA-based imaging with a minimum device requirement.

An improved aperiodic OPA design based on large antenna spacing

In practical large-scale optical phased array (OPA) design, large antenna spacing is required to accommodate the device size and the routing area. Therefore, under the traditional uniform antenna arrangement, grating lobes result in very limited field of view (FOV). Fortunately, the grating lobes limiting the FOV can be suppressed by aperiodic OPA. Here, we analyze the performance of the aperiodic OPA with large spacing, and propose an improved aperiodic OPA design by proper antenna arrangement to increase the side mode suppression ratio (SMSR). For a 512-channel aperiodic OPA whose antenna spacing is larger than 10λ and smaller than15λ, >15dB SMSR is achieved.

Incoherent light imaging using an optical phased array

Recent advances in silicon photonics have enabled large-scale optical phased arrays for applications such as beam steering and directional light detection. However, to date, these results have only been applied to coherent light. Many applications, including passive imaging with natural illumination, require operation using incoherent and/or broadband light. Here, we implement an optical phased array designed for these applications using a planar, fractal, path length-matching architecture known as an “H-tree.” We demonstrate electronic beamsteering and natural light imaging using this flat, broadband, photonic-integrated device.

Large-scale optical phased array using a low-power multi-pass silicon photonic platform

Optical phased arrays are a promising beam-steering technology for ultra-small solid-state lidar and free-space communication systems. Long-range, high-performance arrays require a large beam emission area densely packed with thousands of actively phase-controlled, power-hungry light emitting elements. To date, such large-scale phased arrays have been impossible to realize since current demonstrated technologies would operate at untenable electrical power levels. Here we show a multi-pass photonic platform integrated into a large-scale phased array that lowers phase shifter power consumption by nearly 9 times. The multi-pass structure decreases the power consumption of a thermo-optic phase shifter to a P π of 1.7 m W / π without sacrificing speed or optical bandwidth. Using this platform, we demonstrate a silicon photonic phased array containing 512 actively controlled elements, consuming only 1.9 W of power while performing 2D beam steering over a 70 ∘ × 6 ∘ field of view. Our results demonstrate a path forward to building scalable phased arrays containing thousands of active elements.

A Monolithically Integrated Large-Scale Optical Phased Array in Silicon-on-Insulator CMOS

A large-scale monolithic silicon nanophotonic phased array on a chip creates and dynamically steers a high-resolution optical beam in free space, enabling emerging applications in sensing, imaging, and communication. The scalable architecture leverages sub-array structure, mitigating the impact of process variation on the phased array performance. In addition, sharing control electronics among multiple optical modulators in the scalable architecture reduces the number of digital-to-analog converters (DACs) required for an $N^{2}$ array from $\mathcal {O}(N^{2})$ to $\mathcal {O}(N)$ , allowing a small silicon footprint. An optical phased array for 1550-nm wavelength with 1024 uniformly spaced optical grating antennas, 1192 optical variable phase shifters, and 168 optical variable attenuators is integrated into a 5.7 mm $\times$ 6.4 mm chip in a commercial 180-nm silicon-on-insulator RF CMOS technology. The control signals for the optical variable phase shifters and attenuators are provided by 136 DACs with 14-bit nonuniform resolution using 2.5-V input-output transistors. The implemented phased array can create 0.03° narrow optical beams that can be steered unambiguously within ±22.5°.

Blueprint for Large-Scale Silicon Optical Phased Array Using Electro-Optical Micro-Ring Pixels

We propose a modularized architecture of a large-scale optical phased array (OPA) on a silicon on insulator (SOI) platform, using electro-optical (EO) pixels. Each pixel contains a directional coupler, a micro-ring phase shifter, and a grating optical antenna, on a compact configuration of area 50 μm × 50 μm, with optical and electrical interconnections. Moreover, we present an exemplary blueprint of an OPA consisting of 32 × 32 EO pixels, which sets the width of the main lobe as 0.04° × 0.04° and the field of view as 1.78°. By applying an over-coupled condition, the modulation efficiency and the accompanying intensity modulation are balanced, thus, the OPA performance is not severely degraded. The discussion on the fabrication tolerance shows that the proposed architecture is robust and feasible regarding the state-of-the-art fabrication process, and the performance of the main lobe width and field of view can be further optimized by a larger system size and smaller pixel size. Furthermore, the complexity of interconnections linearly depends on the number of rows and columns, making it highly scalable.

Large-Scale Silicon Photonic Circuits for Optical Phased Arrays

We review recent advances in integrated large-scale optical phased arrays. The design and fabrication of large-scale optical phased arrays using silicon photonic circuits are discussed from device designs including the directional couplers, thermo-optic phase shifters, and optical nanoantennas, to system studies including phased array synthesis and noise analysis. By taking advantage of the well-developed silicon complementary metal-oxide-semiconductor (CMOS) fabrication technology, several large-scale integrated silicon photonic phased arrays are demonstrated, including two passive-phased arrays (64 × 64 and 32 × 32) with the ability to generate complex holographic images, an 8 × 8 active phased array for dynamic optical beamforming, and an 8 × 8 active antenna array with amplitude apodization. These optical phased array demonstrations, with up to 12 000 integrated optical elements, represent the largest and densest silicon photonic circuits demonstrated to date.