Research On Optical Signal Processing Chip Based On Thin-film Lithium Niobate

With the development of optical communication technology,the tunable all-optical network is becoming a research hotspot,and the optical signal processing chip that can modulate the signal in the all-optical network synchronously become the key optoelectronic device.The traditional optical spatial mode control technology based on liquid crystal spatial light modulator has the disadvantages of slow control speed and small control range.In this thesis,an optical signal processing chip based on array waveguide grating(AWG)is studied,and the optical signal processing chip is designed and tested on a thin-film lithium niobate platform.The main research contents are as follows(1)An AWG-based optical signal processing chip is proposed.The chip monolithically integrates AWG,modulator array and reflector array on thin-film lithium niobate,and can control the amplitude and phase of each frequency component of the input optical signal seperately.By processing the incident light signal in the frequency domain,functions such as optical filters and arbitrary waveform generators can be realized.(2)An AWG-based optical signal processing chip is designed.The basic principle of AWG is introduced and the theoretical model of AWG is established based on Fourier diffraction theory.The AWG has the center wavelength of 1550 nm and the wavelength interval of 50 pm is designed on thin-film lithium niobate.The AWG has 100 channels.The basic principle of multimode interferometer(MMI)is expounded,and the 1×2MMI,2×2MMI and S-bend structures are simulated and optimized.The Mach-Zehnder Modulator(MZM)and reflector are designed based on MMI.(3)The fabrication process of the optical signal processing chip is introduced,the layout of the optical signal processing chip is designed,and a test system for the optical signal processing chip with polarization control is developed.The fabricated optical signal processing chip is characterized using this test system.The measured results show that the channel spacing of the AWG is 50 pm and the half wave voltage of the MZ modulator is about 2.5 V with the response time less than 0.5μs,which preliminarily verified the proposed optical signal processing chip scheme.(4)The optical signal processing chip is optimized.Shallow etching is used in the array waveguide area with TE mode,and the length difference of the array waveguide is shortened.Therefore,the phase error accumulated in the arrayed waveguide can be reduced,and the insertion loss of the device together with the crosstalk between channels can be reduced.The simulation results show that the insertion loss of AWG is about 3 d B,and the crosstalk is less than 20d B.At the same time,the MMI structure is optimized,and the coplanar electrode structure is implemented for the MZ modulator array.The V_πL of the MZ modulator is about 8.76V·cm by simulation.In conclusion,this thesis proposes an optical signal processing chip based on thin-film lithium niobate,and manufactures and tests it,which preliminarily verifies the feasibility of the scheme,and further optimizes it according to the test results.