Research On Broadband Silicon-Based Power Splitter And Polarizer Based On Subwavelength Structure

Photonic integrated circuit(PIC)is widely used in communication systems because of its high precision,small size and large amount of transmitted information.With the advent of the post-Moore era,the performance of photonic integrated devices has been subject to higher requirements.Compared with cascaded conventional non-integrated devices,photonic integrated devices can be integrated under the same chip,which is crucial to reduce insertion loss and improve accuracy in a limited volume.The performance of widely used basic photonic integrated devices such as optical power splitters,polarizers,polarization beam splitters,directional couplers,and micro-ring resonant cavities still need to be further improved and their size still needs to be further reduced.To address this problem,this paper focuses on the new design of broadband optical power splitter and broadband polarizer by introducing subwavelength structure,optimizing the device structure size and considering the influence of processing tolerance to achieve larger bandwidth and smaller size than the traditional optical power splitter and polarizer,which can be applied as basic devices in the field of optical communication.First,using the finite time domain differential algorithm,the effects of coupling length and gap,sub-wavelength grating(SWG)structure period and duty cycle,and adiabatic cone length on the silicon-based optical power splitter proposed in this paper were studied,and a 3d B power splitter with a low loss of less than 0.45 d B in the O,E,S,C,L,and U bands(1.26μm ～ 1.675 μm)was realized,and the length of the spectroscopic region was only 5 μm.By continuing to optimize the duty cycle distribution trend,the duty cycle decreases in the spectroscopic direction,and a 3 d B power splitter with a loss of less than 0.45 d B in the 1.25μm ～ 2.04 μm band,that is,790 nm ultra-large bandwidth,is obtained.Secondly,the effects of curved sub-wavelength grating structure and double adiabatic cone structure on the performance of silicon-based polarizer were analyzed by using finite time domain differential algorithm,and the effects of duty cycle distribution,maximum duty cycle of grating strips in curved sub-wavelength grating,number of grating strips,coupling gap and double adiabatic cone length on silicon-based polarizer were studied,and a high-performance silicon-based polarizer with a polarization extinction ratio of more than 39 d B,a loss of less than 1 d B and a bandwidth of more than 228 nm was realized under a footprint of only 6 μm × 10 μm.Finally,the research content of this paper is summarized in a general way,and the application prospects of the two silicon-based passive devices designed are prospected,and the photonic integrated chip used in the field of miniaturized interferometric fiber gyroscopes can be built by using the broadband silicon-based power splitter and polarizer based on the sub-wavelength structure proposed in this paper.