Stabilization Of The Exposing Interference Pattern In Holographic Grating Production

When fabricating holographic gratings the exposing interference pattern must be stationary. Normally this is achieved by working in a very stable interferometric environment where special care has been taken regarding low dependence of temperature, stable mechanical and optical components. Despite considerable precautions in these respects, reproducible results are difficult to achieve, especially considering the fabrication of multiple exposure gratings i.e. Fourier synthesis gratings. In our laboratory we have developed a technique for fabrication of holographic gratings by using a reference grating and a servosystem to keep the interference pattern stationary. The reference grating monitors both frequency and phase errors. This method allows us to achieve a high outcome in fabrication without utilizing replicas. It is also possible to reproducibly make Fourier synthesized gratings with selectable phase between the different harmonics.