Nico Correns

Microspectrometer based on holographically recorded diffractive elements using supplementary holograms

The conception and realization of an imaging microspectrometer, limited to an optical volume of 11 x 6 x 5 mm(3), is presented. The spectrometer is based on a multi-order concept and offers an overall spectral bandwidth of 400-1030 nm with better than 2.5 nm resolution in the visible range. The numerical aperture of NA = 0.2 allows an appropriate energy efficiency. As the most essential element of the microspectrometer, a concave diffraction grating with a diameter of 5 mm and an image distance of f = 8.6 mm was manufactured in a holographic recording process. For the recording process the specifications of the concave grating require two diffraction limited point sources in very close proximity. To provide a point source distance below 1 mm a recording concept based on the introduction of a supplementary hologram was employed.