Spatial beam splitting for fully integrated MEMS interferometer

Abstract

In this paper a novel approach for optical beam splitting for MEMS based Fourier transform spectrometer is proposed. This approach is mainly based on spatial truncation of the input Gaussian beam into two symmetric Semi- Gaussian beams using V shape mirror and hence eliminating the use of a beam splitter and allowing the integration of optical spectrometers. It can be used over wide spectral range including infrared and visible region. Unlike the traditional Michelson interferometers which return half of the optical power to the source, the reflected power is negligible. This enables the use of multiple reflecting mirrors increasing the optical path difference by a factor of four. The analytical model describing the beams propagation and interference is derived using Fourier optics techniques and verified using Finite Difference time domain method. Mechanical model providing the mirror displacement to produce the optical pass difference is conducted and verified using finite element method. Mechanical displacement of 160 <i>&mu;m</i> is achieved which is multiplied by a factor of four, resulting is a resolution of 9 <i>nm</i> at wavelength 1.55 <i>&mu;m</i>. Finally, the effect of different design parameters on the interference pattern, interferogram and resolution are demonstrated.