Elimination of a back-reflected TE mode traveling in a TM-mode optical isolator was investigated. The optical isolator had a Mach-Zehnder interferometer that included a polarization-dependent reciprocal phase shifter in one of the arms. The reciprocal phase shift was achieved by an optical path difference between the two arms. By adjustment of the length of the reciprocal phase shifter, the interferometer prevented the back-reflected TE mode from coupling into an input port of the isolator. An extinction ratio of more than 18 dB was obtained against the back-reflected TE mode at a wavelength of 1.55 µm.
© 2002 Optical Society of America
Original Manuscript: April 25, 2002
Revised Manuscript: August 19, 2002
Published: November 20, 2002
Hideki Yokoi, Tetsuya Mizumoto, Shinpei Kuroda, Takafumi Ohtsuka, and Yoshiaki Nakano, "Elimination of a back-reflected TE mode in a TM-mode optical isolator with a Mach–Zehnder interferometer," Appl. Opt. 41, 7045-7051 (2002)