We observed a periodic intensity-noise variation in the output of a Mach–Zehnder interferometer as we changed the arm-length difference in the range of several millimeters. We found that the period of the variation coincided with that expected for the longitudinal-mode separation of the semiconductor laser. The origin of the huge excess noise of a bright fringe (approximately 30 dB above the shot-noise level) was the longitudinal-mode-partition noise that was due to the selective destructive interference of side modes.
© 1997 Optical Society of America
Shuichiro Inoue and Yoshihisa Yamamoto, "Longitudinal-mode-partition noise in a semiconductor-laser-based interferometer," Opt. Lett. 22, 328-330 (1997)