Zhang De-Long, Kang Jian, Wong Wing-Han, Yu Dao-Yin, Pun Edwin Yue-Bun
Opt Lett. 2015 Oct 15;40(20):4715-8. doi: 10.1364/OL.40.004715.
We report an electro-optically tunable optical filter based on a parallel structure of two long period gratings in the two same Ti:LiNbO3 strip waveguides: one 675-μm-pitch grating in one waveguide and another 880-μm-pitch grating in the other waveguide. The stop-band is observed in the 1.1-1.3 (1.4-1.6) μm spectral region for the grating pitch 675 (880) μm. Its contrast increases linearly to ∼30 dB as the voltage is increased to 300 V, and the linearity is similar for the two cases of 675 and 880 μm pitches. Higher than 300 V, the contrast decreases due to photorefractive (PR) effect and/or over-coupling. Accompanying the contrast modulation, the resonant wavelength is simultaneously linearly tuned by making use of the PR effect. For the 675 (880) μm pitch, the tuning range is 160 (200) nm for the 400 (300) V voltage change range. With the two gratings, one can realize >360 nm super-broadband filtering.
我们报道了一种基于两个相同的钛酸锂铌（Ti:LiNbO3）条形波导中两个长周期光栅平行结构的电光可调谐光学滤波器：一个波导中有一个节距为675μm的光栅，另一个波导中有一个节距为880μm的光栅。对于节距为675（880）μm的光栅，在1.1 - 1.3（1.4 - 1.6）μm光谱区域观察到阻带。当电压增加到300V时，其对比度线性增加到约30dB，对于675μm和880μm节距的两种情况，线性度相似。高于300V时，由于光折变（PR）效应和/或过耦合，对比度降低。伴随着对比度调制，利用PR效应同时对谐振波长进行线性调谐。对于675（880）μm节距，在400（300）V电压变化范围内，调谐范围为160（200）nm。利用这两个光栅，可以实现大于360nm的超宽带滤波。
