Phase response characterization of semiconductor saturable absorber for applications in nonlinear optical signal processing and phase-modulated signals regeneration

The phase response of a commercial saturable absorber based on semiconductor quantum wells embedded in a resonant cavity is investigated. The nonlinear absorption change is accompanied by a variation of the spectral phase characteristic. Also, a nonlinear change in the refractive index of the material, induced by the modified carrier density, produces a weak shift in the resonant wavelength of the cavity. These effects can be exploited to realize an optically-controllable phase shifter. Simulations based on a nonlinear model are also carried out in order to investigate the effect of the various cavity parameters and phase response of the device under different operating conditions. The results from this characterization and numerical analysis show that such device can have the potential for practical applications in telecom systems, including dynamic dispersion compensation, tunable nonlinear effects compensation, and nonlinear signal processing and all-optical regeneration of phase-modulated optical signals.