Abstract
The tolerances in manufacturing of fully dielectric diffraction gratings based on the leaky-mode resonance in the st diffraction order can be challenging, especially if the grating design exhibits high diffraction efficiency (DE) only within a comparatively narrow spectral bandwidth. To gain improved control on the spectral bandwidth exhibiting high DE, we implemented a two-step etching approach within the fabrication process of the grating. First, a dry and anisotropic etching step was used for pre-shaping the grating, followed by iterative isotropic wet-etching steps using an alkaline solution (KOH) at a temperature of 90°C to adjust the maximum efficiency around the desired wavelength with high precision. This straightforward method gave us very good control on tailoring the DE as a function of the wavelength and led to the demonstration of DEs as high as in the st diffraction order at a wavelength of 1030 nm and of in the wavelength range between 1020 and 1070 nm. The gratings were used as cavity end mirrors of an Yb:YAG thin-disk laser, generating an output power of 145 W in fundamental mode operation ().
© 2018 Optical Society of America
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