Study On The Light Utilization Efficiency Of Waveguide Array Electro-optical Scanning System

A novel laser scanner, Waveguide Array Electro-optical Scanner(WAEOS),is studied. WAEOS has a lot of advantages, in particular its large scanning area, high scanning frequency, low drive voltage and small bulk. Therefore, it has numerous military and civil applications including, laser radar, optical communications, laser-guided and laser display etc. In this paper, theory and experiment have been used to study the light utilization efficiency of waveguide array electro-optical system. The author’s major contributions are outlined as follows:1. An experimental platform for measuring the light utilization efficiency of WAEOS is established. It is found that the light utilization efficiency of Optical Waveguide Array(OWA) as well as the coupling efficiency between Single Mode Fiber(SMF) and OWA are the main factors on the light utilization efficiency of WAEOS.2. The optical coupling system of SMF-OWA is studied. Its coupling loss and several normal coupling ways are introduced. Then, four coupling modes are simulated by using a specialized design and analysis software. The results show that the coupling ways of butt fiber and self-focusing lens are better than the others.3. Two of the principal factors on the light utilization efficiency of OWA are discussed, namely, the leakage loss and absorption loss. To reduce the leakage loss, an isolation layer with low refractive index growing between substrate and OWA is put forward. The simulation results show that by adopting the isolation layer its leakage loss is reduced to 2% from 38% of the total input power.4. The absorption loss of OWA is studied. Based on the theoretical simulation and the experiment results, extinction coefficients of different parts of OWA are estimated. Then, to reduce absorption loss, a method of growing transition layers between the cladding and core layers is presented. Simulation results show that by using transition layers the light utilization efficiency of OWA is 1.78 times its original structure.5. The far-field intensity distribution of different OWA is also studied. A method of growing absorption layers with higher extinction coefficient between substrate and OWA is proposed. Simulation results show that absorption layers are able to improve the scanning field and to reduce the intensity of scanning sidelobes.