Systems and methods for spectrally broadening seed pulses with a single pass laser amplifier are disclosed. A bulk TM:II-VI polycrystalline material with combined gain and nonlinear characteristic provides passive (cold) spectral broadening of high power seed pulses. Continuous pumping provides more significant spectral broadening. In particular, pulsed pumping of TM:II-VI polycrystalline material (e.g. Cr2+:ZnS, Cr2+:ZnSe, and Cr2+:CdSe) is shown to provide significant spectral broadening to the super continuum generation SCG level. Pulse picking, pump sources, master oscillators and various optical components are described.