Improving the spectral resolution of wedged etalons and linear variable filters with incidence angle.
Compact spectrometers fabricated by placing a wedged etalon or a linear variable filter in front of a linear photodiode array typically do not exhibit the spectral resolution of a parallel filter of the same finesse. A theoretical analysis of the beam emerging from a wedged etalon is shown to predict a comalike aberration, explaining the loss in resolution. This analysis also predicts a focused beam waist whose axial position depends on the incidence angle, indicating that resolution can be improved by placing this waist on the detector. These results are experimentally confirmed in a multicavity linear variable filter to achieve 0.09 nm spectral resolution at 1550 nm.
McLeod
Robert R
RR
Department of Electrical and Computer Engineering, University of Colorado, Campus Box 425, Boulder, Colorado 80309, USA. mcleod@colorado.edu
Honda
Tokuyuki
T