Experimental Investigations on Polarization Switching and Bistability in a 1550 nm VCSEL Subject to Orthogonal Optical Injection With Time-Varying Injection Power

Polarization switching (PS) and polarization bistability (PB) characteristics of a 1550 nm vertical-cavity surface-emitting laser (VCSEL) subject to orthogonal optical injection (OOI) with time-varying injection power are experimentally investigated for the first time. To implement the optical injection, a Mach-Zehnder modulator (MZM) modulated by a triangular radio wave is adopted, and the influences of some typical parameters on the performances of PS and PB are analyzed. Under suitable operation conditions, PB in the VCSEL subject to OOI with time-varying injection power can be observed only for the input power P
₀
of MZM locating within a determined range, and the width of hysteresis loop gradually decreases with the increase of P
₀
from the minimum P
_0,min
to the maximum P
_0,max
. Under different frequency detuning Δ
_ν
between the injection light and the X polarization mode of the VCSEL, the determined ranges of P
₀
required for PB are different. With the variation of Δ
_ν
from a negative value to a positive value, both P
_0,min
and P0,max present a trend of decrease first and then increase. Additionally, with the increase of the modulation frequency, the hysteresis loop width firstly increases rapidly and then gradually tends saturation.