Research On Suspended Coupler Based On SiN Nanowire Waveguide

The silicon photon mode size converter is an important device for connecting a very small device in a silicon-based integrated chip to an externally transmitted signal fiber.It has an indispensable position in the application of an integrated optical path,it can couple the optical signal from the single-mode fiber to the small-sized optical waveguide device with large coupling efficiency and low polarization loss at the output end of the fiber,At the same time,it can also be used to couple the optical signal in the waveguide chip.Output.The device is mated with a single-mode fiber at one end with a fiber-matched mode size;the other end has a mode size that matches the nanowire silicon-based optical waveguide,so the use of the structure can reduce Optical coupling loss between standard single-mode fiber and nanowire silicon-based optical waveguides.In this paper,the converter based on SiN nanowire waveguide is designed and studied.The converter has a working band of about 800 nm.Its core structure is supported by SiO ₂ beams and the bottom is hollowed out.By continuously simulating the design optimization and adjusting the parameters of the structure,high coupling efficiency and low polarization loss are obtained.In this paper,the structure of the converter is designed with two kinds of cases:cone-covered on the top and no cone-cover.The two structures are compared and found that the performance of the two is similar,but a layer of cone is deposited on the top.The shape of the waveguide requires a layer of reticle,so only the converter structure without the tapered cover is fabricated.The calculated coupling efficiency of the TE mode is 87%?coupling loss is-0.6 dB/facet?,TM is 81%?coupling loss is-0.9 dB/facet?,polarization is less sensitive,1-dB bandwidth is 34 nm and 32 nm,respectively,1-dB alignment tolerances are±0.8?m both horizontally and vertically.The TE and TM modes have a coupling efficiency of 85%?coupling loss of-0.7 dB/facet?with a tapered structure stack,1-dB bandwidth is 37 nm,a low polarization loss,and 1-dB alignment tolerances of TE and TM modes about±1?m both horizontally and vertically.The experimental data obtained is in TE mode,when the wavelength is 810 nm,the transmission loss of the SiN waveguide is-0.07 dB/mm,and the coupling loss of the tapered fiber and the nano-taper is-3.06 dB/facet;in the TM mode.The transmission loss of the SiN waveguide is-0.06 dB/mm,and the coupling loss of the tapered fiber to the nano-taper is-3.67 dB/facet.The coupling loss between the flat-head fiber and the SiN cantilever type single converter is-2.50 dB/facet?coupling efficiency is about 56%?and TM mode coupling loss is about-8 dB/facet?coupled efficiency?when the mode is TE mode.Approximately 15%)The 1 dB coupling alignment tolerance of the flat-head fiber to the SiN cantilevered mode size converter is greater than 1.25?m on both the X and Y axes.