Spatial optical beam steering with an AlGaAs integrated phased array

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 m 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. In this Letter, an integrated approach on siliconon-insulator (SOI) is taken where the phase differences are introduced on a photonic integrated circuit and the light is subsequently coupled off chip. Phase control is done here using the thermo-optic effect in silicon. Silicon has a relatively large thermo-optic coefficient being ‫ץ‬n / ‫ץ‬T = 1.86ϫ 10 −4 K −1 at a wavelength of 1550 nm resulting in an easy, low-cost, and stable way of achieving phase modulation [4].In [5] a similar approach is used with an AlGaAs integrated waveguide array. A continuous deflection over an angle of 0 . 41°at a wavelength of 900 nm with a FWHM divergence of 0 . 09°is reported. The phase modulation was done electro-optically with indium tin oxide/AlGaAs Schottky junctions. The array spacing is much larger than the spacing achievable with the present fabrication technologies on SOI, making the latter attractive for beam steering.A schematic of the component can be found in Fig. 1. The component was fabricated on SOI with an oxide thickness of 2 m and a silicon thickness of 220 nm using standard complementary metal-oxide semiconductor (CMOS) processes in the Interuniversity MicroElectronics Center (IMEC) [6]. Two etching steps are used: one of 220 nm for etching the waveguides and the multimode interference (MMI) splitters and the second of 70 nm to etch the grating couplers. The structure is excited with transverseelectric (TE) polarized light through a lensed fiber via the facet of a 3-m-wide integrated access waveguide. This waveguide is tapered to a width of 500 nm and then split with a MMI-splitter tree into sixteen 800 nm wide parallel waveguides, spaced 2 m apart. On top of each waveguide a second-order diffraction grating intended for light outcoupling is shallow etched, characterized by a period of 630 nm and a duty cycle of 0.5 for efficient outcoupling of the TE polarized light. The grating coupler consists of 50 periods. After approximately 35 periods the measured outcoupled light has decayed by a factor of 1/e 2 . Since transverse-magnetic (TM) polarized light will not be coupled out efficiently by the grating couplers owing to the difference in effective index, the component is highly polarization dependent. Afterward a benzocyclobutene (BCB) layer of approximately 1 m is spun on top and a titanium electrode is sputtered with a thickness of approximately 100 nm. While the BCB does not allow for a very efficient heat transfer to the optical waveguide, this technique requires a minimum of processing to demonstrate the beam steeri...

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“…In [5] a similar approach is used with an AlGaAs integrated waveguide array. A continuous deflection over an angle of 0 .…”

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confidence: 99%

Off-chip beam steering with a one-dimensional optical phased array on silicon-on-insulator

et al. 2009

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“…Several free-space optical beam steering devices have been proposed in literature. These include micro-electromechanical mirrors [20,23], acousto-optic deflectors [38], on-chip grating modules [39][40][41][42] and liquid crystals [43]. However, these devices have drawbacks such as the need for local powering, slow steering speed, small steering angles and separate communication channels.…”

Section: Optical Beam Steering Principlementioning

confidence: 99%

Free-space transmission with passive 2D beam steering for multi-gigabit-per-second per-beam indoor optical wireless networks

Cao

Tangdiongga

et al. 2016

Opt. Express

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“…Meanwhile, some LPA systems based on fiber, 3 waveguide, 4 Lanthanum-modified Lead ZirconateTitanate, 5 and liquid crystal 6 were provided theoretically. However, it is difficult to obtain a good performance practically because the performance of the LPA system is affected by many factors.…”

Section: Introductionmentioning

confidence: 99%

Laser-phased-array beam steering controlled by lithium niobate waveguides

Yang

Wang

2013

Opt. Eng

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Abstract. A laser steering system based on the Ti-diffusion lithium niobate (LiNbO 3 ) waveguides is presented. A phase shifter based on the LiNbO 3 waveguide is designed. This waveguide can provide a continuous phase shift for laser-phased-array (LPA) by changing the voltage loaded on it. The theory of irregular LPA based on the Ti-diffusion LiNbO 3 waveguide phase shifter is studied numerically and experimentally. Beam steering with an angle of 1.37 deg is gained by a 1 × 3 array setup that agrees well with the theory.

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Spatial optical beam steering with an AlGaAs integrated phased array

Cited by 58 publications

References 15 publications

Off-chip beam steering with a one-dimensional optical phased array on silicon-on-insulator

Off-chip beam steering with a one-dimensional optical phased array on silicon-on-insulator

Free-space transmission with passive 2D beam steering for multi-gigabit-per-second per-beam indoor optical wireless networks

Laser-phased-array beam steering controlled by lithium niobate waveguides

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