High-resolution aliasing-free optical beam steering
20 Aug 2016-Vol. 3, Iss: 8, pp 887-890
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.
Citations
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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
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.
326 citations
Cites background from "High-resolution aliasing-free optic..."
...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: Using the same silicon nitride platform and phased array architecture, it is demonstrated that the first large-aperture visible nanophotonic phased array at 635 nm with an aperture size of 0.064°×0.074° is demonstrated, to the best of the authors' knowledge.
Abstract: We demonstrate passive large-scale nanophotonic phased arrays in a CMOS-compatible silicon photonic platform. Silicon nitride waveguides are used to allow for higher input power and lower phase variation compared to a silicon-based distribution network. A phased array at an infrared wavelength of 1550 nm is demonstrated with an ultra-large aperture size of 4 mm×4 mm, achieving a record small and near diffraction-limited spot size of 0.021°×0.021° with a side lobe suppression of 10 dB. A main beam power of 400 mW is observed. Using the same silicon nitride platform and phased array architecture, we also demonstrate, to the best of our knowledge, the first large-aperture visible nanophotonic phased array at 635 nm with an aperture size of 0.5 mm×0.5 mm and a spot size of 0.064°×0.074°.
244 citations
TL;DR: 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.
Abstract: 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°.
217 citations
Cites background from "High-resolution aliasing-free optic..."
...At optical frequencies, electronically controlled solid-state optical phased arrays [10]–[21] have been demonstrated since 1990s with less than 128 array elements by either heterogeneous or monolithic integration....
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...The largest tunable optical phased array reported to date [21] has only 128 array elements....
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...2 visualizes the tradeoff between beam-steering range and beamwidth for the largest value of κ N/d from [21],...
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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
References
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TL;DR: In this paper, a 16 element one-dimensional optical phased array on silicon-on-insulator with a field-of-view of 23.5 degrees of freedom was investigated.
Abstract: Optical beam steering can find applications in several domains such as laser scanning, LiDAR (Light Detection And Ranging), wireless data transfer and optical switches and interconnects. As present beam steering approaches use mechanical motion such as moving mirrors or MEMS (MicroElectroMechanical Systems) or molecular movement using liquid crystals, they are usually limited in speed and/or performance. Therefore we have studied the possibilities of the integrated silicon photonics platform in beam steering applications. In this paper, we have investigated a 16 element one-dimensional optical phased array on silicon-on-insulator with a field-of-view of 23. Using thermo-optic phase tuners, we have shown beam steering over the complete field-of-view. By programming the phase tuners as a lens, we have also shown the focusing capabilities of this one-dimensional optical phased array. The field-of-view can easily be increased by decreasing the width of the waveguides. This clearly shows the potential of silicon photonics in beam steering and scanning applications.
49 citations
TL;DR: A pseudo-random, two-dimensional optical phased array (OPA) concept based on tandem injection locking of 64-element vertical cavity surface emitting laser (VCSEL) arrays, providing large OPA scaling potential.
Abstract: We demonstrate, both theoretically and experimentally, a pseudo-random, two-dimensional optical phased array (OPA) concept based on tandem injection locking of 64-element vertical cavity surface emitting laser (VCSEL) arrays. A low cavity-Q VCSEL design resulted in an injection locking optical power of less than 1 μW per VCSEL, providing large OPA scaling potential. Tandem injection locking of two VCSEL arrays resulted in measured controllable optical phase change of 0-1.6π. A high quality beam formed with suppressed grating lobes due to the pseudo-random array design was demonstrated with performance close to simulated results. A preliminary 2.2° x 1.2° beam steering example using the tandem arrays was also demonstrated.
38 citations
TL;DR: In this paper, a corrugated waveguide was used as a free space grating coupler for use in optical phased arrays for large angle optical beam steering, achieving 15° of steering with wavelength tuning, with an average longitudinal beam width of 0.3°.
Abstract: We present the corrugated waveguide as a free space grating coupler for use in optical phased arrays for large angle optical beam steering. Compared with conventional shallow etched gratings, the corrugated waveguide requires only a single patterning step while achieving lithographically defined index contrast. We achieve 15° of steering with wavelength tuning, with an average longitudinal beam width of 0.3°. To prevent optical crosstalk from grating-assisted coupling in a corrugated waveguide array with small element spacing, the photonic bandgap of a 2D photonic crystal is used to optically isolate each array element in a 16 element array.
35 citations
TL;DR: The first tunable laser is directly modulated in burst mode for upstream transmission over up to 25 km of standard single mode fiber and error free transmission over 4 channels across the C-band is demonstrated.
Abstract: We propose and demonstrate asymmetric 10 Gbit/s upstream--100 Gbit/s downstream per wavelength colorless WDM/TDM PON using a novel hybrid-silicon chip integrating two tunable lasers. The first laser is directly modulated in burst mode for upstream transmission over up to 25 km of standard single mode fiber and error free transmission over 4 channels across the C-band is demonstrated. The second tunable laser is successfully used as local oscillator in a coherent receiver across the C-band simultaneously operating with the presence of 80 downstream co-channels.
24 citations
TL;DR: It is found that the thermo-optic phase tuning departs the expected quadratic dependence and is well characterised by a quartic dependence upon heater current or voltage.
Abstract: The ability to steer optical beams, crucial to the operation of high-speed optical wireless links may be achieved using optical phased array antennas which have significant potential in this application. The beam formed by the phased array antennas is steered by tuning the relative phase difference between the adjacent antenna elements which may be achieved nonmechanically. In this paper, the characteristics and behaviour of two dimensional optical phased arrays with a structure composed of 2 × 2, 4 × 4, and 16 × 16 antenna elements in beam steering are verified. The wavelength beam steering of −0.16°/nm is measured along the θ direction with a required steering range (between main lobes) of 1.97° within a −3 dB envelop of 5° extent in the θ direction and 7° extent in the Φ direction. To achieve two-dimensional beam steering, thermo-optic beam steering can be used in Φ direction. It is found that the thermo-optic phase tuning departs the expected quadratic dependence and is well characterised by a quartic dependence upon heater current or voltage.
14 citations