Research On Properties Of Silicon-based On-chip Devices For Infrared Modulation

Silicon-based optical chips techniques can be compatible with modern semiconductor wafer processing.It provides the possibility of low-cost,miniaturization,and large-scale integration for systems such as optical spectroscopy,detection,communications,and computing systems.Silicon has a very low absorption loss and a large refractive index in the infrared region,and infrared wave has unique advantages in areas such as communications and material detection.Therefore,the scientific and industrial communities in various countries have continuously invested in the theory and application of various infrared optical systems based on siliconbased optical chips in recent years.Admittedly,with the development of semiconductor technology,silicon-based optical chips have been rapidly developed in recent years.Due to material and volume limitations,many of the infrared components used in free space cannot be effectively transplanted to silicon-based chips,with the problems such as large insertion loss and low efficiency.Therefore,in this thesis,utilizing low absorption losses and high refractive index of silicon,we study several novel infrared devices on silicon-based chips.First,a silicon-based subwavelength grating reflector is studied.The influence of internal mode coupling of high-contrast gratings on infrared light transmission was analyzed.Through introducing guided modes into the high-contrast gratings,an ultrabroadband,high-reflectivity sub-wavelength grating reflector is realized,due to the coupling of the Fabry–Pérot mode,the waveguide mode,and the grating mode.The ratio of the high reflection frequency range to the center frequency is up to 30%,and the high reflection angle range is more than 40 degrees.The effects of different substrate and the dispersion characteristics of the multimode coupled reflector were studied.Second,a sub-wavelengh silicon-based on-chip filter is studied.The effect of asymmetrical structures on the bound state optical modes in grating structures such as waveguide mode and grating mode is studied.By breaking the symmetry of the grating structure,a normal incidence Fano resonance filter on an optical chip is realized.The effects of different coupling modes on the performance of the filter's resonant frequency and quality factors are studied.The effect of different coupling modes and different processing conditions on the performance of the filter is analyzed.Then,a on-chip silicon-based polarization rotator is studied.The evolution of modes in a silicon-based rectangular waveguide is studied,and an inverse-taper waveguide coupler that can effectively improve the free-space-to-silicon waveguide coupling efficiency is designed.Based on simulation,a two-layer waveguide rotator is fabricated.The insertion loss,extinction ratio,rotation angle and other properties are studied.Finally,based on the polarization rotator,on-chip controlled NOT gates and swap gates that can be used for quantum computation on are studied.Using the onchip polarization rotator and on-chip polarization splitters,path controlled NOT gates and polarization controlled-not gates were studied.On-chip swap gates are designed using paths and polarization controlled NOT gates.The insertion loss and operation matrix of the quantum gates are measured.