Experimental Investigation on the Characteristics of All-Optical Modulation of Optical Microfiber Coupler

In this paper, we investigate the characteristics of all-optical modulation via thermo-optic effects of an optical microfiber coupler (OMC) and the theoretical analysis and experimental results are shown. The intensity modulation and the phase modulation efficiency are proportional to the length of the OMC' waist region, the pump light intensity, etc. We experimentally characterize the OMC, presenting that stable intensity and phase modulation can be realized by pumps at microwatts level. For OMC' intensity modulation, the modulation bandwidth is measured to be 50 kHz under 1.7 mW pump light intensity. We also demonstrate OMC's phase modulation function, and the frequency response characteristics of the OMC phase modulator shows similar properties with the OMC's intensity modulation, which mainly depends on the waveguide structures of the OMC' waist region and the heat conduction property of the waveguide materials. These results are valuable for the development of all-optical modulators and all-optical tunable filters based on subwavelength scales optical fiber, and hold great potential in laser and optical sensing applications.