[6a-C14-1~14] 3.13 Semiconductor optical devices

[6a-C14-8] Effect of longitudinal mode changes for the self light mixing in multi mode semiconductor laser

〇Chinami Takagi¹, Kei Sassa¹, Keizi Kuroda¹, Yuzo Yoshikuni¹ (1.Kitasato Univ.)

Keywords:Self light mixing, Doppler measurements

In the Doppler measurement by self light mixing, the signal intensity strongly depends on the distance between the laser and the sample. Although strong peaks appear at integral multiples of the equivalent resonator length of the laser, weak peaks are observed in the middle of strong peaks. In this research, we focus on weak peaks and investigate the reason why weak peaks appear by observing signal waveforms.When comparing the signal waveforms in the strong peak and the weak peak, a periodic waveform of higher frequency is observed in the weak peak, and the frequency is almost double the strong peak. Around the strong peak, the threshold gain of the adjacent modes changes inversely at the phase of the returning light and the even and odd order longitudinal modes alternately oscillate, so it is considered that the instantaneous mode spacing is doubled.