Gratings for tunable lasers: using multidielectric coatings to improve their efficiency.

The first results of a theoretical and experimental study are presented showing that a significant enhancement of the efficiency of gratings used as wavelength selectors for cw tunable lasers may be achieved with adequate dielectric coatings. It is found that, in some cases, the energy absorbed by the grating surface can be reduced by a factor >2. The output power of a cw Rh640 dye laser was practically multiplied by the same factor. It seems that holographic gratings are more adaptable than are ruled gratings to this utilization.