InGaAs/GaAs saturable absorber for diode-pumped passively Q-switched dual-wavelength Tm:YAP lasers

We demonstrate the first use of InGaAs/GaAs as a saturable absorber in the Q-switching of a diode pumped Tm(3+) doped laser operating at the wavelengths of 1940 nm and 1986 nm. The influence of the semiconductor saturable absorber's (SESA) position and thermal lens effect on the Q-switch characteristics was investigated. With a pump power of 35 W, the maximum pulse energy of 28.1 microJ with a pulse width of 447 ns at the pulse repetition frequency (PRF) of 43.7 kHz was obtained by selecting the appropriate position of the SESA.