ASE suppression in a high energy Titanium sapphire amplifier.

The energy required to generate ultrashort pulses with petawatt peak power from a Ti:sapphire laser system is a few tens of joules. To achieve this, the final amplifier must have a gain region of around 5 cm diameter that is uniformly pumped at high fluence. The high level of amplified spontaneous emission (ASE) in such an amplifier will seriously degrade its performance unless care is taken to minimise the transverse gain and the internal reflections from the crystal edges.