[OPTICAL REVIEW Vol. 7, No. 6 (2000) 550-554]

Effect of Linewidth Enhancement Factor on Doppler Beat WaveformObtained from a Self-Mixing Laser Diode

Sahin Kaya ÖZDEMIR,1,2 Shigenobu SHINOHARA1 and Hirofumi YOSHIDA1

1Faculty of Engineering, Shizuoka University, 3-5-1, Johoku, Hamamatsu, 432-8561 Japan

(Received June 22, 2000; Accepted August 10, 2000)

The asymmetry and fringe inclination of the sawtooth-like waveform observed in the self-mixing signal obtained from a semiconductor laser with optical feedback enable the direction discrimination of line-of-sight motion of external target surfaces. We investigated the effects of linewidth enhancement factor and feedback strength on the asymmetry and the direction of fringe inclination of the signal by numerical simulations. For the first time, we show that direction of the fringe inclination is determined not only by the direction of the target motion but also by the value of the linewidth enhancement factor.

Key words : self-mixing effect, linewidth enhancement factor, optical feedback, Doppler beat waveform, fringe inclination