Optical Performance Reasearch And Process Improvement Of Lithium Niobate Modulator

High speed electro-optic modulators are the part in large capacity optical fibertransmission network and high speed photo-electronic information process system. It istherefore urgent to develop high speed electro-optic modulators.In this thesis, we focus on the key technologies in the design and fabrication ofLithium Niobate (LiNbO3) electro-optic modulators. We review the devices’development and application around the world. Finite difference beam propagationmethod (FD-BPM) is utilized to simulate the loss of Y-branch optical waveguide andthe optimal parameters of waveguide are acquired.Three main loss characteristics of the modulator, i.e., the optical fiber-waveguidecoupling loss, the Y-branch waveguide loss, and loss by shape deformation induced bytemperature fluctuation. Firstly, we compare the loss of different types of Y-branchstructure, with varying branch angle, branch interval and then optimize the structure ofY-branch waveguide. The optimized design of Y-branch waveguide can reduce bendingloss of the modulator effectively. By calculating coupling loss of opticalfiber-waveguide, we can confirm the reference control range of optical fiber-waveguidecoupling alignment. We then measure the modulator performances under differenttemperatures and use ANSYS to simulate the coupling structure of Lithium Niobatemodulator when it’s subjected to temperature variations. According to the stressdistribution of fiber-waveguide coupling position, elastic displacement, we analyses thecauses of loss, in view of which we put forward to use low temperature glass solders toreplace the high-temperature UV adhesive.Furthermore, we design several schemes and optimum proposals based on differentcauses of loss. Under the scheme suggested by this thesis, we design some parts of itsinternal structure construct the whole package and, test the modulator performance. Wefinally give some suggestions to improve the reliability of the device.