Multiple quantum well passive mode-locking of a NaCl color center laser

Using multiple quantum well (MQW) saturable absorbers, we passively mode locked a NaCl color center laser to produce transform‐limited, pedestal‐free pulses with τ as short as 275 fs and peak power as high as 3.7 kW. Because of exciton ionization with a 200±30 fs time constant, the MQW shows a fast absorption recovery that is comparable to our pulse widths. This fast component plays a major role in pulse shaping and may limit the pulse width. We also show that the wavelength for the short pulses can be tuned from 1.59 to 1.7 μm by choosing MQWs with different band gaps.