We theoretically investigate an all-optical isolator under arbitrary linearly polarized fundamental wave (FW) input in an optical superlattice (OSL). The scheme is based on simultaneously phase matching the first-order Type I (oo-e) quasi-phase-matching (QPM) second-harmonic generation (SHG) process and higher-order Type 0 (ee-e) QPM SHG process in an OSL with a defect inserted in an asymmetrical position. Simulation results show that the contrast ratio of the all-optical isolator can maintain close to 1 under arbitrary linearly polarized FW. Thus, an all-optical isolator based on an OSL that is not sensitive to the direction of linear polarization can be realized. We also show that, with the defect in a strong asymmetry position, the length of the defect can be designed flexibly to maintain a high contrast ratio. Additionally, if the length of the OSL is longer, the nonreciprocal response can be realized for low optical intensities.
© 2011 Optical Society of America
Original Manuscript: July 21, 2011
Revised Manuscript: September 2, 2011
Manuscript Accepted: September 14, 2011
Published: November 23, 2011
Liang Yuan, Jianhong Shi, and Xianfeng Chen, "All-optical isolator under arbitrary linearly polarized fundamental wave in an optical superlattice," Appl. Opt. 50, 6352-6357 (2011)