Hun Yong PARK, Chung-Hun PARK, Byung-Chul HWANG¹, Seung Gol LEE, Beom-Hoan O, El-Hang LEE and Se-Geun PARK^*

Micro-Photonics Advanced Research Center, School of Information and Communication Engineering, Inha University, #253 Yonghyun-Dong, Nam-Gu, Incheon 402-751, Korea
¹OLED Production Department, SKC Co., Ltd., #460 Chonhung-Ri, Chonan, Chungnam 330-836, Korea

(Received September 29, 2004; Accepted September 28, 2005; Revised September 9, 2005)

A wavelength tunable thermo-optic filter has been designed and fabricated for 1550 nm transmission. It has a Fabry–Perot resonator at the center with two sets of distributed Bragg reflector mirrors at both ends. The filter is fabricated as a free-standing membrane of alternating poly-Si and SiO₂ films surrounded by a thick silicon frame. The membrane is buckled due to the residual stress. Because of the buckling effect, high tuning efficiency of more than 0.17 nm/°C is observed. When the filter has a buckled surface, the incident light normal to the filter should have a range of non-zero angle of incidence to the membrane, which is dependent on the degree of buckling that depends again on the temperature. The transmittance calculations which integrate each incoming ray from a different incident angle show good qualitative agreement with the temperature dependence of the center wavelength and bandwidth.

Key words: thermo-optic filter, tunable filter, membrane, buckling, Fabry–Perot resonator

^*Corresponding author. E-mail address: sgpark@inha.ac.kr