High efficient transmission- and reflection gratings for femtosecond pulse compression applications

The invention of Chirped Pulse Amplification (CPA)1 has opened up a wide range of applications for pulsed lasers with picosecond to femtosecond pulse lengths. This technique uses the large bandwidth of short pulse lasers for temporally stretching, amplification and subsequent re-compression of the laser pulse. For the compression almost exclusively gratings are used. For this particular application dielectric gratings have clear advantages concerning efficiency and high damage threshold. Here, we report on the fabrication of high efficient, large area pulse compression gratings operating in transmission or reflection mode with efficiencies of more than 97%. Highly efficient dielectric reflection gratings for 1030 nm and 1057 nm wavelength with a groove density of 1740 lines per mm were developed. These gratings consist of a stack of alternating SiO2/Ta2O5 double layers and show efficiencies of more than 97% over an area of 70x25 mm2. In addition to the reflection gratings we present large area efficiency enhanced pulse compression gratings (transmission e2PCGs). Typical transmission gratings for high groove densities of > 1480 lines per mm and wavelength > 1000 nm suffer from high reflection losses due to the desired Littrow-configuration.