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.
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Posted Content•
TL;DR: In this paper, a modified rotating element electric field vector (modified REV) method was proposed to calibrate the antenna array initial condition of an optical phased array (OPA) device.
Abstract: This paper presents a modified rotating element electric field vector (modified REV) method to calibrate the antenna array initial condition of an optical phased array (OPA) device. The new method follows a similar sequential individual antenna phase calibration process while it modifies the algorithm to avoid possible {\pi} phase error in traditional REV when large initial phase distribution and finite optical power measurement accuracy present. We show that the method produces statistically more accurate and predictable calibration result which is highly desired in practice.
6 citations
Cites background from "High-resolution aliasing-free optic..."
...[14-17] can provide fairly good calibration in some cases however they generally cannot avoid local extremum uncertainty (which is a severe issue for most OPA with larger-than-wavelength-spaced antennae) and are not scaled well with the size of the antenna array....
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01 Mar 2022
TL;DR: In this article , the waveguide liquid claddings were replaced with a 2D beam steering of an optical phased array, achieving a maximum steering angle of 10° with RI from 1.0 to 1.63 at 940 nm.
Abstract: We present the replacing of waveguide liquid claddings to implement 2D beam steering of an optical phased array. A maximum steering angle of> 10° was achieved with RI from 1.0 to 1.63 at 940 nm. © 2022 The Author(s).
6 citations
TL;DR: In this paper , the authors combine all-optical encoders with wavelength-division multiplexing devices to implement spectro-temporal encoding on the illumination light for parallel detection and fast spectral scanning with only one laser and one single photodetector.
Abstract: Light detection and ranging (LiDAR) with scanning beam has been widely used in autonomous driving and large-scale manufacturing, where the fast-changing scene is of great interest. However, the acquisition rate of current LiDAR is limited by beam steering speed and the round-trip delay, hindering the development of video-rate LiDAR. Here, we uniquely combine all-optical encoders with wavelength-division multiplexing devices to implement spectro-temporal encoding on the illumination light. Parallel detection and fast spectral scanning can be achieved with only one laser and one single photodetector. Our result shows the fastest single-pixel LiDAR to date, and the detection speed can be multiplied with scalability. We demonstrate 3.56-fold improvement of speed for a maximum of 75 m detection range compared with a serial LiDAR. A record acquisition rate of 21.38 MHz for a maximum of 25 m detection range is obtained. This approach has the potential to break the limitation on current ultrafast single-pixel LiDAR and opens a new paradigm for ultrafast-frame-rate imaging systems.
6 citations
TL;DR: In this article, a backward-emitting SiN optical phased arrays (OPAs) incorporating a reinforced grating vector is proposed, which provides efficient wavelength-tuned beam steering along the longitudinal direction.
Abstract: Silicon nitride (SiN) optical phased arrays (OPAs) have emerged as a potential alternative to their silicon counterparts, due to their potential use in enhanced solid-state light detection and ranging. Grating antennas based on a SiN waveguide suffer from a limited beam steering efficiency, owing to the relatively lower effective refractive index of the waveguide. To mitigate this limitation, we propose and demonstrate a backward-emitting SiN OPA incorporating a reinforced grating vector, which provides efficient wavelength-tuned beam steering along the longitudinal direction. Two backward-emitting OPAs were primarily characterized by their steering efficiency and the spectral emission for the main lobe, and they were compared with a forward-emitting device using a weakened grating vector. The results indicated that strengthening the grating vector for the antenna improved the beam steering efficiency but adversely affected the dependence of its directionality on the wavelength. The directionality was particularly inspected, with respect to major design parameters for the grating antennas, including the pitch and etch depth of a SiN grating, as well as the thickness of a buried oxide and SiN core layer. The proposed backward-emitting OPA scheme is expected to significantly promote its feasibility as an advanced beam scanning device.
6 citations
Cites background from "High-resolution aliasing-free optic..."
...While several studies attempted to develop the emission behavior in the lateral direction [5], [19], [20], the waveguide gratings constituting the antenna have not been suitably designed for beam steering efficiency in the longitudinal direction....
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Dissertation•
01 Jan 2016
TL;DR: In this article, the design and experimental results of an integrated chip-scale frequency-modulated continuous-wave LIDAR system with optical phased arrays have been presented, which has the capability of measuring both distance and velocity simultaneously with a 20 mm resolution and a 2 m range.
Abstract: Light detection and ranging (LIDAR) has become an ubiquitous ranging technology. LIDAR systems are integral to almost all autonomous vehicles and robotics. Most LIDAR systems today use discrete free-space optical components and utilize a mechanical apparatus for beam steering. Apart from the relative high cost of the system, this mechanical apparatus limits the scan rate of the LIDAR system while increasing both size and complexity. This leads to concerns about long-term reliability, especially in harsh environments. In this thesis, the design and experimental results of an integrated chip-scale frequency-modulated continuous-wave LIDAR system are presented. This system has the capability of measuring both distance and velocity simultaneously with a 20 mm resolution and a 2 m range. Its functionality is then extended by utilizing optical phased arrays as a transmitter and receiver for solid-state beam steering. The phased array utilized has a grouped cascaded phase shifter architecture and is shown to have a steering range of 46∘×36∘. This is the first integrated coherent LIDAR system based on optical phased arrays. In order to have a viable LIDAR system with optical phased arrays, high beam powers and large aperture sizes are needed. A silicon nitride distribution network is used to enable high on-chip power because of the low material nonlinearities. An ultra-high main beam power of 520 mW is reported. A phased array is demonstrated with an ultra-large aperture size of 4×4 mm2, achieving a record-small and near diffraction limited spot size of 0.021∘×0.021∘ with a side lobe suppression of 10 dB. This is the largest optical phased array to date by an order of magnitude and shows the scalability of optical phased arrays. Finally, an optical phased array at a visible wavelength of 635 nm is shown with an aperture size of 0.5×0.5 mm2 and a spot size of 0.064∘×0.074∘. This demonstration moves large-scale integrated photonics into the visible spectrum and has potential applications in bathymetric LIDAR. Thesis Supervisor: Michael R. Watts Title: Associate Professor 3
6 citations
Cites background or methods from "High-resolution aliasing-free optic..."
...This was demonstrated in [21] to achieve a steering range of 80∘....
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...This ultra-small spot size is over an order of magnitude smaller in area than the previous demonstration in [21] and allows for a long-range propagation....
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...The far field of the array was measured with an InGaAs IR camera and a two-lens imaging system [21], and is shown in Fig....
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...14∘ [21], which we estimate to be a ∼500×500μm2 effective aperture....
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...Finally, ultra-large-angle beam steering of has been achieved with a small spot size [21]....
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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
01 Aug 1998
TL;DR: The digital display engine (DDE) as discussed by the authors is based on a single DMD device having array dimensions of 800/spl times/600 elements, illuminated by a metal halide arc lamp through a compact optics train.
Abstract: A period of rapid growth and change in the display industry has recently given rise to many new display technologies. One such technology, the Digital Micromirror Device/sup TM/ (DMD), developed at Texas Instruments, represents a unique application of microelectromechanical systems to the area of projection displays. In this paper, we describe a representative example of a DMD-based projection display engine, the digital display engine (DDE). The DDE is based on a single-DMD device having array dimensions of 800/spl times/600 elements, illuminated by a metal halide arc lamp through a compact optics train. The engine is designed for portable and fixed conference-room graphics and video display applications, and many design decisions were made to tailor the engine for its intended venue. The design of the projection engine optics and electronics is discussed, along with the basic operation, manufacture, and reliability of the DMD itself.
642 citations
TL;DR: A 16-channel, independently tuned waveguide surface grating optical phased array in silicon for two dimensional beam steering with a total field of view of 20° x 14° and full-window background peak suppression of 10 dB is demonstrated.
Abstract: We demonstrate a 16-channel, independently tuned waveguide surface grating optical phased array in silicon for two dimensional beam steering with a total field of view of 20° x 14°, beam width of 0.6° x 1.6°, and full-window background peak suppression of 10 dB.
373 citations
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
TL;DR: The photonic integrated circuit (PIC) consists of 164 optical components including lasers, amplifiers, photodiodes, phase tuners, grating couplers, splitters, and a photonic crystal lens and exhibited steering over 23° x 3.6°.
Abstract: In this work we present the first fully-integrated free-space beam-steering chip using the hybrid silicon platform. The photonic integrated circuit (PIC) consists of 164 optical components including lasers, amplifiers, photodiodes, phase tuners, grating couplers, splitters, and a photonic crystal lens. The PIC exhibited steering over 23° x 3.6° with beam widths of 1° x 0.6°.
283 citations