Optical Phased Array Design Based On 2 μm Waveband

Optical Phased Array(OPA)is a directly beam scanning technology.In the antenna array,the specific phase difference between adjacent antennas can make the light constructive interference in a certain direction that diffracted by antenna,thereby produce a specific direction beam.By adjusting the phase difference between adjacent units,the beam can be achieved scanning.OPA uses laser light as the incident light source.In the optical frequency band,the laser light source has a smaller wavelength than the traditional microwave band,which can make OPA form a smaller spot and have higher scanning accuracy.In addition,compared with the traditional mechanical control beam scanning technology,optical phased array technology has many advantages such as faster scanning speed,higher spatial resolution,and more stable structure.At the same time,with the development of on-chip optical device integration,especially when silicon-based photonics technology is combined with traditional semiconductor CMOS,with the help of mature CMOS technology,large-scale optoelectronic integration can be achieved,which makes silicon-based optical phased arrays integrated in Optical chip,improve performance and reduce volume.This research direction is a hotspot in recent years.The current silicon-based phased array is designed based on the 1550 nm band,but it has a large Two-photon Absorption(TPA)effect in this band,so it greatly limits the output of optical power.In addition,how to form a large-scale effective emission aperture to make the obtained beam quality light spot smaller is also a valuable research direction.This paper analyzes and discusses the difference of the non-linear effects of the power loss of the laser propagating in the silicon waveguide between 2 μm and 1550 nm bands.The analysis shows that the 2 μm band has smaller two-photon absorption,less nonlinear loss,and greater saturation power when propagating in the waveguide.Therefore,an optical phased array antenna structure will be designed based on the 2 μm band.First,we analyze the working principle of the optical phased array,and compare and summarize the phase shifter and beam splitter of each design scheme.Then,based on 3D FDTD simulation,we simulate and design the grating antenna,beam splitter and phase shifter.Finally,we design a large-aperture optical phased array with CMOS compatible technology.Based on the analysis of the effect of the effective optical aperture on the size of the diffraction spot,we found that a larger effective emission aperture can form a smaller far-field spot.Therefore,it is necessary to design a large-diameter optical phased array.Compared with the currently reported silicon-based optical phased array antenna design,the dissipation of the 2 μm band laser in the silicon-based waveguide is smaller than that in 1550 nm band.The design based on the 2 μm band in this paper has smaller non-linear loss,and the large-aperture optical phased array designed under the full etching process can obtain smaller spot size and better beam quality.