Optical Bistability From Domain Formation in Terahertz Quantum Cascade Lasers

摘要

Novel transverse-mode behavior and bistability are observed in spectral and far-field measurements of terahertz-distributed feedback quantum cascade lasers. Prior to onset of negative differential resistance (NDR) at the maximum superlattice current, lasing is exclusive to a single (TM00) transverse mode. Precisely at NDR, lasing switches to a distinct (TM01) transverse mode. The spatial redistribution of optical power in the NDR regime is explained in terms of formation of bias domains localized to the lateral edges of the waveguide. As the bias voltage is reduced below NDR, hysteresis is observed as continued lasing on the TM01 mode. Photon-assisted current transport is proposed as the dominant mechanism for the bistability.