Spectral Study on the Effects of Angle-Tuned Filter Wedge Angle Parameter to Reflecting Characteristics
YU Kan1, HUANG De-xiu1, 2, YIN Juan-juan1, BAO Jia-qi1
1. Wenhua College, Huazhong University of Science and Technology, Wuhan 430074, China 2. Wuhan National Laboratory for Optoelectronics, Wuhan 430074, China
Abstract：Three-port tunable optical filter is a key device in the all-optic intelligent switching network and dense wavelength division multiplexing system. The characteristics of the reflecting spectrum, especially the reflectivity and the isolation degree are very important to the three-port filter. Angle-tuned thin film filter is widely used as a three-port tunable filter for its high rectangular degree and good temperature stability. The characteristics of the reflecting spectrum are greatly influenced not only by the incident angle, but also by the wedge angle parameter of the non-paralleled wedge thin film filter. In the present paper, the influences of the wedge angle parameter to the reflectivity and the half bandwidth are analyzed, and the reflecting spectrum characterstics are simulationed in different wedge angle parameter and polarity. The wedge angle-tuned thin film filter with 0.8° wedge angle parameter is fabricated. The experimental results show that keeping the wedge angle the same orientation to the incident angle will worsen the reflectivity and the rectangular degree of the reflecting spectrum. However, keeping the wedge angle orientation reverse to the incident angle will enhance the reflectivity and decrease the bandwidth, which will give higher reflectivity and isolation degree to the three-port filter than that of high parallel degree angle-tuned thin film filter.
Key words：Thin film filter;Wedge angle;Angle-tuned;Reflecting spectrum;Isolation degree
