Temperature-Insensitive Dual-Comb Filter Based on Multimode Interference Ti : LiNbO $_{3}$ Waveguide

A temperature-insensitive dual-comb filter has been demonstrated for the first time by multimode interference based on a Ti : LiNbO$_{3}$ channel waveguide. The phase difference between comb filters was about 180 $^{\circ}$. We only observed less than ${\pm}$0.125-nm variation of the center wavelength of the filter during temperature change from 20 $^{\circ}$C to 50 $^{\circ}$C. The measured extinction ratio and channel spacing of the comb filter were about ${-}$25 dB and 3.2 THz, respectively.