Highly dispersive 100%-efficiency transmission gratings without reflection losses

Due to the rapid progress in high-power laser systems, there is an increasing demand for highly efficient damage resistant components. One decisive role in the power limitation of such systems, e.g. chirped pulse amplification setups (Strickland and Mourou, 1985), is played by the grating pair, which is used to recompress the amplified optical pulses. In order to achieve pulse peak powers in the megawatts range, these gratings have to be dielectric, where they can be optimized either for reflection or transmission. Up to now, one of the main disadvantages of transmission gratings was the problem of significant reflection losses in the case of high dispersion and grazing incidence. These losses are typically in the range above 10% for grating periods near half of the wavelength. However, we have developed a simple grating layout, which can be optimized to avoid any reflection losses, thus achieving theoretically 100% diffraction efficiency in the highly-dispersive -1st diffraction order, when the grating is illuminated in Littrow-mounting. In this layout a rectangular surface relief grating is etched into a fused silica substrate and afterwards covered by a second silica substrate. By optimizing the geometrical parameters of this embedded grating, the reflection can be suppressed completely, while simultaneously all the transmitted light is deflected to the -1st order.