Imaging gratings with modulated blaze realized by a combination of holography and reactive ion beam etching

In a wealth of applications the requirement of high spectral resolution is accompanied by low light energy arriving from the objects under investigation. Typically high and constant diffraction efficiency would be beneficial in the whole spectral range of interest. A way to enhance the dynamic of a spectrometer is the adaptation of the spectral efficiency characteristic of the diffraction grating to the spectral properties of the remaining parts, in particular the sensor and the light source. For surface relief gratings the saw tooth like or so called ‘blazed’ gratings achieve maximal diffraction efficiency. However, on a conventional blaze grating the physical boundary conditions lead to a spectral efficiency dependency with a quite narrow maximum. In the majority of spectral sensor applications a different efficiency characteristics would improve the device performance considerably. We present a new method to tune the spectral characteristic of blazed gratings by a combination of interference lithography and successive reactive ion beam etching employing special masks. Measuring data of the resulting spectrometer system with the modified grating type will be presented.