Compact spectrometer modelling based on wavelength-scale stationary wave Fourier transform in integrated optic

摘要

Recently, a new generation of high-resolution ultra-compact spectrometers (SWIFTS) has been investigated in integrated optics. Its principle consists of sampling an interferogram obtained by a stationary waves in an optical waveguide without moving parts. Then a Fourier transform of the interference pattern gives the spectral response of the optical source under test. The sampling is obtained thanks to metallic nanowires set upon the surface of the waveguide. Only a small part of the light, proportional to the light under the metallic element is scattered outside. Then this radiated part is detected on a camera through an optical lens. In this paper, this device is modelized using an Aperiodic Fourier Modal Method allowing simulation of a long SOI waveguide composed of very small metallic elements described by a complex refractive index. We demonstrate the possibility of obtaining the spectral response with this method. Instead of using a classical lens associated to a camera, we also modelize an entire compact device composed of a linear photo-detector array above the waveguide separated by a peculiar gap. This gap is chosen in order to image the interferogram without damaging the initial interferogram. Spectral resolution close to 4 nm is obtained with 1 mm waveguide length.