Design Of Monolithic Integrated Adaptive Two-Wave Mixing Photorefractive Interferometer

With the increasing demands of society and technology to acquire,transmit,process and store information,the information network system composed of traditional discrete devices is becoming more and more complex and requires more and more energy consumption.In the traditional optical signal sensing and processing system,the two-wave mixing interferometry of photorefractive crystal,which can monitor dynamic strain,has attracted extensive attention of scholars because it can provide multi-channel dynamic sensing and does not need electronic feedback to actively compensate for any quasi-static drift.However,its system configuration has disadvantages such as large occupied space,various types of optical components,complex optical path structure,difficult optical alignment and sensitivity to vibration.These shortcomings are surmountable under laboratory conditions,but difficult to handle for real-life applications.Thanks to the rapid development of photonic integrated circuits,monolithic integration can effectively solve these shortcomings.Based on the above background,a monolithic integrated adaptive two-wave mixing photorefractive interferometer is designed.The structure consists of semiconductor optical amplifier,curved waveguide,directional coupler,unbalanced Mach-Zender structure,crossed waveguide,electrode sheet and photodetector.The main work of this paper is as follows:(1)Through the study of the two-wave mixing transmission characteristics based on photorefractive crystals and the understanding of the sensing demodulation principle of fiber Bragg gratings,the experimental research of two-wave mixing demodulation system based on In P:Fe is carried out.The fiber Bragg gratings sensor with a center wavelength of1549.89 nm and a bandwidth of 0.2 nm is pasted on a piezoelectric ceramic plate,a dynamic signal with a frequency of 1 k Hz and a strain of 4 ?? is applied to the fiber Bragg gratings sensor by driving the piezoelectric ceramic plate with a function generator to simulate the received dynamic strain for system demodulation research.The experimental results show that the applied dynamic strain is effectively demodulated,and the two-wave mixing demodulation system based on In P:Fe is feasible.(2)Based on the simulation principle of the finite element numerical analysis software,the unbalanced Mach-Zender structure used in the In P:Fe two-wave mixing demodulation system is numerically analyzed based on photon integrated circuit,and two Mach-Zender modulator structures based on photon integrated circuit are optimized.The transmission demodulation characteristics of balanced and unbalanced Mach-Zender modulators are analyzed.The results show that in the Mach-Zender structure,the waveguide transmission changes sinusoidally,and the optical power output switches between the two output ports alternately according to the variation of the applied voltage and the difference of different waveguide lengths.Changing the length difference can result in a certain initial phase difference between two waveguide transmissions.(3)For two commonly used fiber Bragg gratings sensors with 0.1 nm and 0.2 nm linewidths,combining the analyzed two wave mixing transmission modulation principle and the fiber Bragg gratings wavelength demodulation principle,the optimized design of monolithic integrated adaptive two-wave mixing photorefractive interferometer structure is performed using finite element numerical analysis software: A reasonable optical waveguide model is constructed,the curvature radius of the curved waveguide is optimized,the appropriate length of the directional coupler is selected,the unbalanced Mach-Zender structure is designed,and the optimal incident angle of the two-wave mixing is determined.The feasibility of the optimized structure was verified by numerical analysis,and the demodulation theoretical curve of the transmitted signal light with time was obtained.The research results lay the foundation for the miniaturization of the two-wave mixing demodulation system based on In P:Fe.