Study On The Cascaded Double-ring Enhanced Fourier Transform Chip Spectrometer

On-chip spectrometer is important for on-chip spectral analysis in applications such as chemical and biological sensors,etc.Different on-chip spectrometers are developed by using arrayed waveguide gratings,echelle diffraction grating,photonic crystal,ring resonator array and on-chip Fourier transform(FT)spectrometer.However,they suffer with very limited bandwidth in order to achieve high spectral resolution.To solve this problem,a cascaded double-ring enhanced FT on-chip spectrometer is proposed in this article.This spectrometer is based on silicon on insulator(SOI).By cascaded double tunable high Q ring resonators to produce Vernier Effect,a narrow bandwidth filter with a wide tunable range was formed in order to improve the spectral resolution of the spectrometer.The high-resolution and large-bandwidth on-chip spectrometer is comprised of this tunable filter and a FT spectrometer.The on-chip spectrometer has the advantages of a large bandwidth(1500-1600nm),a high spectral resolution(0.3nm),portability,compatibility with CMOS process,low cost and easily integrated with other silicon-based optical waveguide devices.In this paper,the electromagnetic field theory analysis of the optical waveguide used in the chip spectrometer is carried out,the principle and performance parameters of the micro-ring resonator are analyzed and introduced,the transfer function of the cascaded double-ring resonator is derived using the transfer matrix method,and the vernier effect is introduced.Finally,the MZI structure was analyzed theoretically and the transmission spectrum formula were derived.The chip spectrometer was simulated,the radius of the ring resonator and the MZI parameters were determined,a retrieved algorithm considering dispersion was proposed,combined with the double-ring transmission spectrum,the input spectrum was successfully retrieved,and the manufacturing process of the spectrometer chip was briefly introduced,and the physical image of the chip and Electron micrograph of the corresponding structure.Two coupling methods of chip and optical fiber are introduced,the package of chip and light array is completed,and two test systems based on wavelength detection and power detection are built.The chip spectrometer is tested,and the modified method is obtained by studying and discussing the results.