Frequency-induced polarization switching and bistability in a 1550 nm VCSEL subject to parallel optical injection

Abstract

We experimentally investigate frequency-induced polarization switching (PS) and bistability (PB) characteristics in a 1550 nm vertical-cavity surface-emitting laser (1550 nm VCSEL) subject to parallel optical injection, for which the polarization direction of the injection light is along with the direction of dominant polarization mode in the solitary 1550 nm VCSEL. The results show that, for a 1550 nm VCSEL under parallel optical injection with frequency detuning ∆ν (= νinj − ν0, where νinj is the frequency of injection light and ν0 is the frequency of dominant polarization mode of the solitary 1550 nm VCSEL), type I PS (the dominant polarization mode switches from Y-polarization mode with a shorter wavelength to X-polarization mode with a longer wavelength) and type II PS (the dominant polarization mode switches from X-polarization mode to Y-polarization mode) can be observed through continuously scanning the frequency of injection light. Moreover, the values of ∆ν required for generating PSs are dependent on the variation route, namely frequency-induced PB phenomenon occurs. In the region with negative ∆ν, there exist two hysteresis loops, whose widths are seriously influenced by the injection power and the biased current.