Imaging gratings for multiorder microspectrometers realized by interference lithography using supplementary holograms

The strong demand for rugged and miniaturized spectrometers is driven by applications such as in-line process control in pharmacy or in agri-food business. In this contribution we present the concept and the realization of a miniaturized optical spectrometer working in a multi-order principle. The basic principle allows high optical performance while simultaneously the necessary construction space shrinks drastically. Employing this concept, we developed an imaging micro spectrometer with an optical volume of 11x6x5mm³. The detectable bandwidth covers a spectral range from UV to NIR and the spectral resolution reaches up to 2.3 nm for the UV/VIS-range. Additionally, unlike to the majority of competing miniaturization concepts the numerical aperture of 0.2 permits an adequate energetic efficiency. The most decisive element of the micro spectrometer is the concave imaging grating. To manufacture the element in high quality we developed a sophisticated interference lithographic configuration. Especially the implementation of supplementary holograms offers the possibility to generate high quality wave fronts on an advancing small-sized scale.