Theoretical and Numerical Investigations of Wavelength Bi/Multistability in Semiconductor Ring Lasers

Wavelength bi/multistability in semiconductor ring lasers is studied both theoretically and numerically based on a multimode model with nonlinear effects arising from carrier density pulsation, carrier heating, spectral hole-burning, and four-wave mixing included. Wavelength bi/multistability is explained theoretically, and conditions required for wavelength bi/multi-stable operation are derived analytically. It shows the dependence of wavelength bi/multistability on device size and other device and material properties. Radius range within which the device is wavelength bi/multistable is calculated based on the derived expressions. Both the theory and calculations are verified by numerical simulations and supported by previously reported experimental observations on wavelength bi/multistable semiconductor ring lasers. The results indicate that semiconductor microring/microdisk lasers with radius down to 10 μm could still support wavelength bi/multistable operation.