| A space-variant variable-dispersion micro-spectrometer has been designed, fabricated, and tested. This spectrometer allows the dispersion to be varied on a pixel-by-pixel basis across the one-dimensional entrance slit. Micro-electro-mechanical mirrors are located at the entrance slit and direct light to one of three different diffraction gratings. A standard grating spectrometer geometry is used to achieve diffraction-limited performance across the 500–1000 nm wavelength range. Spectral resolutions ranging from 5 to 20 nanometers are achieved.; Micro-optics fabrication techniques are employed to fabricate the spectrometer. Grayscale optical lithography using a custom high-energy beam-sensitive (HEBS) photomask was used to fabricate the spectrometer mirrors in photoresist. High-frequency noise inherent to the HEBS process was smoothed with a reflow technique to obtain smooth surface profiles.; Blazed gratings were written using direct-write electron-beam lithography in SU-8. It is shown that SU-8, which has traditionally been used as a very thick resist for micro-electro-mechanical systems (MEMS) applications, is suitable for fabricating both diffractive and refractive optical elements.; The spectrometer was tested with a variety of optical sources. These include a variety of lasers and elemental discharge tubes. The optical performance of the fabricated spectrometer closely matches the design specifications. |
