Spectral shaping filter for broadband amplifiers

We present the design and implementation of a high-damage threshold spectral shaping filter that can be used to counteract gain narrowing in broadband laser amplifier systems. In contrast to earlier approaches to this problem, the filter has a wide range of tunability in both reflectivity and center wavelength. The shape of the reflectivity curve enables the production of an apodized output spectrum with a clean transform limit. We demonstrate the use of this filter in both regenerative and multipass Ti:Sapphire amplifier systems, yielding super-Gaussian amplified spectra of 70-80 nm width.