Fresnel diffraction effects in Fourier-transform arrayed waveguide grating spectrometer
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2007
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The Optical Society Of America
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Abstract
We present an analysis of Fourier-transform arrayed waveguide gratings in the Fresnel diffraction regime. We report a distinct spatial modulation of the interference pattern referred to as the Moire-Talbot effect. The effect and its influence in a FT AWG device is explained by deriving an original analytical expression for the modulated field, and is also confirmed by numerical simulations using the angular spectrum method to solve the Fresnel diffraction integral. We illustrate the retrieval of spectral information in a waveguide Fourier-transform spectrometer in the presence of the Moire-Talbot effect. The simulated device comprises two interleaved waveguide arrays each with 180 waveguides and the interference order of 40. It is designed with a Rayleigh spectral resolution of 0.1 nm and 8 nm bandwidth at wavelength λ~1.5 µm. We also demonstrate by numerical simulations that the spectrometer crosstalk is reduced from -20 dB to -40 dB by Gaussian apodization.
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© 2007 Optical Society of America.
The financial support of the Spanish Ministry of Education and Science under project TEC2005-02180 and ”Slab Waveguide Spatial Heterodyne Spetrometer project”, Contract 9F028-064201/007/MTB, Space Technology Development Program, Canada Space Agency are acknowledged.