Intracavity frequency doubling of an InGaAs diode laser passivelyQ-switched with GaAs saturable absorber

Abstract

A mathematical model describing the dynamic emission of the intracavity frequency doubling (IFD) of a Q-switched InGaAs/KTP diode laser with a GaAs saturable absorber has been developed. The suggested model describes the temporal behavior of the diode laser system, GaAs saturable absorber and the KTP crystal. This model allows studying the impact of the variations of the input pumping diode laser parameters on the characteristics of the IFD of a passive Q-switched InGaAs/KTP output pulse. The simulation shows that the effect of the two-photon absorption plays an important role in the formation of the output laser pulse. Moreover, the nonlinear losses in the GaAs wafer can limit the obtainable pulse power. The numerical calculations show that the Q-switching process eliminates the tail of the original diode laser pulse and gives single peak picosecond output pulses. A method for deduction of the rate equation parameters is presented. The rate equations can be resolved analytically using small-signal measurements. Moreover, a reduction of the unknown parameters has been described based on the treatment of the threshold of the steady-state and small-signal response methodology.