▎ 摘　　要

We numerically analyzed a graphene optical phase modulator with a Si or Ge waveguide operating at a mid-infrared wavelength. We found that the change in operating wavelength from a near-infrared wavelength to a mid-infrared wavelength enables phase modulation with a significantly small optical loss at a realistic bias voltage. We analyzed the wavelength dependence of the modulation characteristics in the wavelength range from 1.55 to 10 mu m, which revealed that the minimum insertion of 4 dB with 1 dB optical loss change during phase modulation can be achieved at a wavelength of 4 mu m. The phase modulation efficiency was expected to be 0.045 V.cm. Thus, we can obtain a practical graphene optical phase modulator at a wavelength of 4 mu m, which will be useful for optical communication and sensing. (c) 2018 The Japan Society of Applied Physics.