Design and fabrication of the GaAs integrated optical chip for fiber optical gyroscope

An integrated optical chip for fiber optical gyroscope (FOG) is designed and fabricated on GaAs. To achieve a high modulation efficiency and a small chip size, a deeply etched waveguide structure is employed, and accordingly a multimode interference (MMI) coupler is used as the 1 × 2 power splitter. The size of the chip is about 8.5 mm × 0.5 mm, which is much smaller than that of LiNbO₃-based chips. The experimental results show that the extinction ratio (ER) of the TE mode to the TM mode is over 26 dB and the value of V _π·L of the phase modulators is 18 V · cm. The method to further lower V _π is discussed.