Research On The Characteristic Matrix And Sidelobe Of Acousto-Optical Tunable Filter

The dissertation mainly has three components as follows:1. The characteristic matrix analysis of acousto-optic tunable filterThe acousto-optic tunable filter is high-speed optical splitting device. AOTF has been basic light-splitting device for spectral monitoring as they offer fast tuning speed, broad filtering bandwidth,large angular aperture. In this part, through the analysis of AOTF, we use a matrix to sum up the characteristics of AOTF. Based on the matrix, we get the orthogonal polarizing method in the Near-infrared spectral monitoring and verify it in experiment. The characteristic matrix is very important to the design and analysis of optical path system with AOTF.2. The sidelobe reduction of acousto-optic tunable filterFeeble information was picked up from spectrum in the Near-infrared spectral monitoring system, so spectral measurement device must have high spectral resolution and signal-to-noise ratio, then the characteristic of AOTF as the core of light-splitting system is very important. Sidelobe is an important parameter to AOTF, and has a direct effect on the spectral purity, so research about the sidelobe of AOTF is very significant for the near-infrared spectral monitoring requesting high spectral purity. Large research indicates changing transducer geometry leads to change of the acoustic intensity distribution, then sidelobe will be changed. In this section, we calculated the acoustic intensity distribution of different transducers, and designed acousto-optic tunable filter(AOTF) based on different transducers. Through the experiment, we find sidelobe can be reduced by changing the transducer geometry.3. Finite Element - Artificial Transmitting Boundary Method It is very important to the calculation of the waveguide field in the integrated optics, the finite element method (FEM) and beam propagation method (BPM) is newly formulated for the analysis of the waveguide field, but they can not deal with the boundary well. In this part we introduce the transmiting boundary to deal with the boundary and combine it with FEM. we call it Finite Element-Artificial Transmitting Boundary Method, and calculate the 2-D acoustical intensity distribution on the substrate region of tapered acoustical directional couplers to test the validity of the method.