Abstract: An equation of the modulator optical transmittance and the optical axis orientation of the quarter-wave plate is derived according to the principle of LiNbO3 crystal electro-optic modulation. The output characteristic of the crystal electro-optic modulation based on the quarter-wave plate is analyzed by numerical calculation. The result shows that whenever the quarter-wave plate rotates an angle of π/4, the linear modulation, non-frequency doubling modulation or frequency doubling modulation periodically occurs in turn, and this is in agreement with the experimental result.

Key words: electro-optic modulation, LiNbO3 crystal, quarter-wave plate