Ultra-wide Two-dimensional Beam Steering By Silicon Integrated Optical Phased Array

Phased arrays is an array system which can achieve beam steering by the phase control of each array element.Compared to the traditional mechanical optical beam scanners,phased arrays performs better in response speed,resolution,directivity.Optical phased arrays(OPA)works in optical spectrum,which could be widely used in light detection and ranging(LiDAR),optical communications,holography,and laser printing.With the development of the CMOS-compatible silicon photonic technology,silicon integrated optical phased array holds the promise of achieving low-cost,compact,robust and energy-efficient beam scanning technology.We propose an alternative approach to realize ultra-wide two-dimensional beam steering by silicon integrated OPA.A dot matrix scanning method,using the phase control and grating emitters with different periods,is conceived to design the OPA device without the requirement of tunable lasers.Firstly,this paper investigated the research status of OPA.Two-dimensional(2D)beam steering by silicon integrated OPA is mainly realized with two methods.One employs phase control in one direction and tunable laser in the other direction,the other method is using phase control in both directions.However,they require tunable laser sources or large numbers of array elements.The large amount of array elements brings a big challenge to manufacture,power consumption,and control electronics,and the tunable laser is expensive,and in particular its tuning range limits the steering range of OPA.Next,the principle of the slab waveguide and the waveguide grating coupler based on silicon substrate is introduced in this thesis,guiding the design of the waveguide grating.The far-field imaging principle of optical phased array is analyzed through the physical model of multi-slit Fraunhofer diffraction.The finite-difference time-domain(FDTD)algorithm is researched to guide the design and simulation of the OPA device.Then,the whole design scheme of the OPA system is presented,and the devices used in the system are designed and simulated.The ridge waveguide with a slab height of 100 nm and a width of 1?m is patterned in the SOI substrate.The grating antennas with a etch depth of 90 nm are etched at the end of the ridge waveguide,with a coupling efficiency of 0.48.Based on MMI structure,the optical switch array and splitter array are designed with high transmission and small size,which are convenient for integration.Finally,the concrete steps to achieve the ultra-wide two-dimensional beam steering is introduced in detail.After optimizing the OPA with irregular spacing,the result of ultra-wide two-dimensional beam steering is obtained by FDTD algorithm.Then the result is compared to the performances of reported researchs.Simulations demonstrate an ultra-wide steering range up to 120°×100°,together with over 16×400 resolvable points using just single-wavelength laser.Moreover,our designed OPA device demands only a part of active elements working simultaneously,which benefits to reduce the electrical power consumption.Our approach provides a promising solution for wide-angle,low-cost,and low-power consumption 2D beam steering devices,especially suitable for solid-state light detection and ranging(LiDAR)systems.