Long-Range LiDAR and Free-Space Data Communication With High-Performance Optical Phased Arrays
TL;DR: In this paper, high-performance integrated optical phased arrays along with first-of-their-kind light detection and ranging (LiDAR) and free-space data communication demonstrators are presented.
Abstract: We present high-performance integrated optical phased arrays along with first-of-their-kind light detection and ranging (LiDAR) and free-space data communication demonstrators. First, record-performance optical phased array components are shown with low-power phase shifters and high-directionality waveguide grating antennas. Then, one-dimensional (1-D) 512-element optical phased arrays are demonstrated with record low-power operation ( $ 1 mW total), large steering ranges, and high-speed two-dimensional (2-D) beam steering ( $ 30 $\mu$ s phase shifter time constant). Next, by utilizing optical phased arrays, we show coherent 2-D solid-state LiDAR on diffusive targets with simultaneous velocity extraction at a range of nearly 200 m. In addition, the first demonstration of 3-D coherent LiDAR with optical phased arrays is presented with raster-scanning arrays. Finally, lens-free chip-to-chip free-space optical communication links up to 50 m are shown, including a demonstration of a steerable transmitter to multiple optical phased array receivers at a 1 Gb/s data rate. This paper shows the most advanced silicon photonics solid-state beam steering to date with relevant demonstrators in practical applications.
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20 Jan 2020
TL;DR: In this paper, a multi-pass photonic platform is integrated into a large-scale phased array that reduces phase shifter power consumption by nearly 9 times, without sacrificing speed or optical bandwidth.
Abstract: 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 ${{\rm P}_\pi }$Pπ of ${1.7}\;{\rm mW/}\pi $1.7mW/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}^\circ \times {6}^\circ $70∘×6∘ field of view. Our results demonstrate a path forward to building scalable phased arrays containing thousands of active elements.
202 citations
TL;DR: This result paves the way for the development and proliferation of low-cost, compact and high-performance 3D imaging cameras that could be used in applications from robotics and autonomous navigation to augmented reality and healthcare.
Abstract: Accurate three-dimensional (3D) imaging is essential for machines to map and interact with the physical world1,2 Although numerous 3D imaging technologies exist, each addressing niche applications with varying degrees of success, none has achieved the breadth of applicability and impact that digital image sensors have in the two-dimensional imaging world3–10 A large-scale two-dimensional array of coherent detector pixels operating as a light detection and ranging system could serve as a universal 3D imaging platform Such a system would offer high depth accuracy and immunity to interference from sunlight, as well as the ability to measure the velocity of moving objects directly11 Owing to difficulties in providing electrical and photonic connections to every pixel, previous systems have been restricted to fewer than 20 pixels12–15 Here we demonstrate the operation of a large-scale coherent detector array, consisting of 512 pixels, in a 3D imaging system Leveraging recent advances in the monolithic integration of photonic and electronic circuits, a dense array of optical heterodyne detectors is combined with an integrated electronic readout architecture, enabling straightforward scaling to arbitrarily large arrays Two-axis solid-state beam steering eliminates any trade-off between field of view and range Operating at the quantum noise limit16,17, our system achieves an accuracy of 31 millimetres at a distance of 75 metres when using only 4 milliwatts of light, an order of magnitude more accurate than existing solid-state systems at such ranges Future reductions of pixel size using state-of-the-art components could yield resolutions in excess of 20 megapixels for arrays the size of a consumer camera sensor This result paves the way for the development and proliferation of low-cost, compact and high-performance 3D imaging cameras that could be used in applications from robotics and autonomous navigation to augmented reality and healthcare A compact, high-performance silicon photonics-based light detection and ranging system for three-dimensional imaging is developed that should be amenable to low-cost mass manufacturing
118 citations
TL;DR: Current AV sensor challenges are highlighted, and the strengths and weaknesses of the perception sensor currently deployed are analyzed, and current factors hindering the affirmation of silicon photonics OPAs and their future research directions are discussed.
Abstract: This paper aims to review the state of the art of Light Detection and Ranging (LiDAR) sensors for automotive applications, and particularly for automated vehicles, focusing on recent advances in the field of integrated LiDAR, and one of its key components: the Optical Phased Array (OPA). LiDAR is still a sensor that divides the automotive community, with several automotive companies investing in it, and some companies stating that LiDAR is a ‘useless appendix’. However, currently there is not a single sensor technology able to robustly and completely support automated navigation. Therefore, LiDAR, with its capability to map in 3 dimensions (3D) the vehicle surroundings, is a strong candidate to support Automated Vehicles (AVs). This manuscript highlights current AV sensor challenges, and it analyses the strengths and weaknesses of the perception sensor currently deployed. Then, the manuscript discusses the main LiDAR technologies emerging in automotive, and focuses on integrated LiDAR, challenges associated with light beam steering on a chip, the use of Optical Phased Arrays, finally discussing current factors hindering the affirmation of silicon photonics OPAs and their future research directions.
101 citations
Cites background from "Long-Range LiDAR and Free-Space Dat..."
...Achievable range (not in Table II): this important LiDAR KPI is not always discussed into published works, but 200 m range is reported in [104], and 150 m in [134]....
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...beam key performance indicators (KPIs), as discussed below, for 26 SiPho OPAs proposed in the last 11 years [98]–[99], [101], [104], [110]–[131]....
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...7c-d); the antennas themselves, usually in the form of gratings or edge or end-fire couplers [103]–[104]....
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TL;DR: The serpentine optical phased array (SOPA) as mentioned in this paper is based on a serially interconnected array of low-loss grating waveguides and supports fully passive, 2D wavelength-controlled beam steering.
Abstract: Optical phased arrays (OPAs) implemented in integrated photonic circuits could enable a variety of 3D sensing, imaging, illumination, and ranging applications, and their convergence in new LIDAR technology. However, current integrated OPA approaches do not scale - in control complexity, power consumption, and optical efficiency - to the large aperture sizes needed to support medium to long range LIDAR. We present the serpentine optical phased array (SOPA), a new OPA concept that addresses these fundamental challenges and enables architectures that scale up to large apertures. The SOPA is based on a serially interconnected array of low-loss grating waveguides and supports fully passive, two-dimensional (2D) wavelength-controlled beam steering. A fundamentally space-efficient design that folds the feed network into the aperture also enables scalable tiling of SOPAs into large apertures with a high fill-factor. We experimentally demonstrate the first SOPA, using a 1450 - 1650 nm wavelength sweep to produce 16,500 addressable spots in a 27x610 array. We also demonstrate, for the first time, far-field interference of beams from two separate OPAs on a single silicon photonic chip, as an initial step towards long-range computational imaging LIDAR based on novel active aperture synthesis schemes.
86 citations
TL;DR: This article introduces a single-chip OPA realized through wafer-scale 3-D integration of silicon photonics and CMOS, and achieves wide-range 2-D steering over 18.25° beamwidth while consuming 20 mW/element average power.
Abstract: With the growing demand for automotive LiDAR and the maturation of silicon photonics platforms, optical phased arrays (OPAs) have emerged as a key technology for solid-state optical beam-steering. In order to meet realistic automotive specifications with OPAs, >500 antenna elements should work reliably under tight power and cost budgets. Existing multi-chip solutions necessitate expensive packaging and assembly to achieve high interconnect density. Even with 2-D monolithic integration, high-voltage drivers to deliver sufficient power to resistive phase shifters typically result in significant overhead in die area and limited power efficiency. In this article, we introduce a single-chip OPA realized through wafer-scale 3-D integration of silicon photonics and CMOS. Flexible and ultra-dense connections with through-oxide vias (TOVs) in our platform resolve the I/O density issue. Moreover, low-voltage L-shaped phase shifters and compact, efficient switch-mode drivers, connected vertically using TOVs, remove wiring/placement overhead and achieve a large active array aperture within a compact die. Our OPA prototype achieves wide-range 2-D steering over 18.5 $^\circ \times $ 16° by leveraging wavelength tuning and phase control, and array scaling up to 125 elements with a large aperture size of $0.5\,\mathrm {mm}\times 0.5\,\mathrm {mm}$ and 0.15 $^\circ \times $ 0.25° beamwidth while consuming 20 mW/element average power. Since our system supports per-element independent phase control, increased sensitivity to process variations in L-shaped shifters is fully compensated by a simple calibration process.
86 citations
References
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TL;DR: This work demonstrates that a robust design, together with state-of-the-art complementary metal-oxide–semiconductor technology, allows large-scale NPAs to be implemented on compact and inexpensive nanophotonic chips and therefore extends the functionalities of phased arrays beyond conventional beam focusing and steering, opening up possibilities for large- scale deployment.
Abstract: A large-scale silicon nanophotonic phased array with more than 4,000 antennas is demonstrated using a state-of-the-art complementary metal-oxide–semiconductor (CMOS) process, enabling arbitrary holograms with tunability, which brings phased arrays to many new technological territories. Nanophotonic approaches allow the construction of chip-scale arrays of optical nanoantennas capable of producing radiation patterns in the far field. This could be useful for a range of applications in communications, LADAR (laser detection and ranging) and three-dimensional holography. Until now this technology has been restricted to one-dimensional or small two-dimensional arrays. This paper reports the construction of a large-scale silicon nanophotonic phased array containing 4,096 optical nanoantennas balanced in power and aligned in phase. The array was used to generate a complex radiation pattern—the MIT logo—in the far field. The authors show that this type of nanophotonic phased array can be actively tuned, and in some cases the beam is steerable. Electromagnetic phased arrays at radio frequencies are well known and have enabled applications ranging from communications to radar, broadcasting and astronomy1. The ability to generate arbitrary radiation patterns with large-scale phased arrays has long been pursued. Although it is extremely expensive and cumbersome to deploy large-scale radiofrequency phased arrays2, optical phased arrays have a unique advantage in that the much shorter optical wavelength holds promise for large-scale integration3. However, the short optical wavelength also imposes stringent requirements on fabrication. As a consequence, although optical phased arrays have been studied with various platforms4,5,6,7,8 and recently with chip-scale nanophotonics9,10,11,12, all of the demonstrations so far are restricted to one-dimensional or small-scale two-dimensional arrays. Here we report the demonstration of a large-scale two-dimensional nanophotonic phased array (NPA), in which 64 × 64 (4,096) optical nanoantennas are densely integrated on a silicon chip within a footprint of 576 μm × 576 μm with all of the nanoantennas precisely balanced in power and aligned in phase to generate a designed, sophisticated radiation pattern in the far field. We also show that active phase tunability can be realized in the proposed NPA by demonstrating dynamic beam steering and shaping with an 8 × 8 array. This work demonstrates that a robust design, together with state-of-the-art complementary metal-oxide–semiconductor technology, allows large-scale NPAs to be implemented on compact and inexpensive nanophotonic chips. In turn, this enables arbitrary radiation pattern generation using NPAs and therefore extends the functionalities of phased arrays beyond conventional beam focusing and steering, opening up possibilities for large-scale deployment in applications such as communication, laser detection and ranging, three-dimensional holography and biomedical sciences, to name just a few.
1,065 citations
TL;DR: With recent successes of laboratory, inatmosphere, and space demonstrations of free-space optical communications, there is no doubt that the technology is ready for operational deployment and significant reduction in system costs can be realized.
Abstract: With recent successes of laboratory, inatmosphere, and space demonstrations of free-space optical communications, there is no doubt that the technology is ready for operational deployment. While these successes have shown that there are no laws of physics against such systems, their estimated system costs are still much too high for serious considerations. Two types of development can reduce the cost dramatically. The first is via the improvement of physical-link communication efficiency by an order of magnitude using photon-counting receivers for vacuum channels, system complexity, weight, and power for space systems can be greatly reduced. The second is through the use of coherent systems in links where clear-air turbulence impairs communication efficiency, and in multiple access applications where coherent processing can reduce the level of interference, significant reduction in system costs can be realized
775 citations
"Long-Range LiDAR and Free-Space Dat..." refers background in this paper
...range direct line-of-sight applications in terrestrial and atmospheric settings [39]....
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TL;DR: This first demonstration of coherent solid-state light detection and ranging (LIDAR) using optical phased arrays in a silicon photonics platform is presented and paves the way for disruptive low-cost and compact LIDAR on-chip technology.
Abstract: We present, to the best of our knowledge, the first demonstration of coherent solid-state light detection and ranging (LIDAR) using optical phased arrays in a silicon photonics platform. An integrated transmitting and receiving frequency-modulated continuous-wave circuit was initially developed and tested to confirm on-chip ranging. Simultaneous distance and velocity measurements were performed using triangular frequency modulation. Transmitting and receiving optical phased arrays were added to the system for on-chip beam collimation, and solid-state beam steering and ranging measurements using this system are shown. A cascaded optical phase shifter architecture with multiple groups was used to simplify system control and allow for a compact packaged device. This system was fabricated within a 300 mm wafer CMOS-compatible platform and paves the way for disruptive low-cost and compact LIDAR on-chip technology.
492 citations
"Long-Range LiDAR and Free-Space Dat..." refers background or methods in this paper
...rect applications ranging from light detection and ranging (LiDAR) [18], free-space data communication [19]–[23], cameras [24]–[27], and image projection [28], [29]....
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...utilizes architectures such as cascaded phase shifters [18], [31] or row-column-based phase shifters [15]....
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20 Aug 2016
TL;DR: In this paper, a two-axis steerable optical phased array with over 500 resolvable spots and 80° steering in the phased array axis (measurement limited) and a record small divergence in both axes (0.14°).
Abstract: Many applications, including laser (LIDAR) mapping, free-space optical communications, and spatially resolved optical sensors, demand compact, robust solutions to steering an optical beam. Fine target addressability (high steering resolution) in these systems requires simultaneously achieving a wide steering angle and a small beam divergence, but this is difficult due to the fundamental trade-offs between resolution and steering range. So far, to our knowledge, chip-based two-axis optical phased arrays have achieved a resolution of no more than 23 resolvable spots in the phased-array axis. Here we report, using non-uniform emitter spacing on a large-scale emitter array, a dramatically higher-performance two-axis steerable optical phased array fabricated in a 300 mm CMOS facility with over 500 resolvable spots and 80° steering in the phased-array axis (measurement limited) and a record small divergence in both axes (0.14°). Including the demonstrated steering range in the other (wavelength-controlled) axis, this amounts to two-dimensional beam steering to more than 60,000 resolvable points.
396 citations
"Long-Range LiDAR and Free-Space Dat..." refers background in this paper
...such as planar lenses [1], reflective optical microelectromechanical systems (MEMS) [2], and integrated optical phased arrays (OPA) [3]....
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...Using an aperiodic pitch can increase the steering range at the cost of an increased background noise and lower main beam efficiency [3], [37]....
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TL;DR: An integrated approach is followed in which a 1D optical phased array is fabricated on silicon-on-insulator in which continuous thermo-optical steering of 2.3 degrees and wavelength steering of 14.1 degrees is reported.
Abstract: Optical phased arrays are versatile components enabling rapid and precise beam steering. An integrated approach is followed in which a 1D optical phased array is fabricated on silicon-on-insulator. The optical phased array consists of 16 parallel grating couplers spaced 2 mum apart. Steering in one direction is done thermo-optically by means of a titanium electrode on top of the structure using the phased array principle, while steering in the other direction is accomplished by wavelength tuning. At a wavelength of 1550 nm, continuous thermo-optical steering of 2.3 degrees and wavelength steering of 14.1 degrees is reported.
299 citations
"Long-Range LiDAR and Free-Space Dat..." refers background in this paper
...in 2009 [5]–[7], OPAs saw tremendous progress in scale,...
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