Wavelength-dispersive device based on a Fourier-transform Michelson-type arrayed waveguide grating

Abstract

We propose a new type of arrayed waveguide grating (AWG) device that operates as a Fourier-transform (FT) spectrometer without the need of scanning elements. The large input aperture size typical of a FT spectrometer eliminates the requirement for a narrow single-mode input waveguide while still achieving high spectral resolution with a markedly increased light-gathering capability (etendue). An example of the device with a resolution of 0.07 nm (approximately 10 GHz) and designed for a silicon-on-insulator platform is presented. The calculated spectra show no noticeable deterioration for aperture widths as large as 40 microm, yielding more than a 50-fold increase in aperture size compared with conventional AWG or echelle grating based devices at the equivalent resolution.

Fresnel diffraction effects in Fourier-transform arrayed waveguide grating spectrometer

“…where λ L is the Littrow wavelength, n g is the group index of the arrayed waveguides, n 0 is the fundamental waveguide mode effective index, n e f f is the effective index in the combiner region, and d is the AWG pitch [5]. The scalar field distribution in proximity of the waveguide array can be obtained by solving the diffraction problem in the Fresnel regime for the periodic waveguide grating structure.…”

“…In order to exploit theétendue benefit of a Michelson interferometer, we proposed the first Fourier-transform Michelson-type arrayed waveguide grating (AWG) spectrometer [5]. This device further develops the concept by Harlander et al who proposed replacing the mirrors in a Michelson interferometer by bulk optics diffraction gratings [6].…”

High-resolution Fourier-transform spectrometer chip with microphotonic silicon spiral waveguides

“…The phase and amplitude errors arising from fabrication imperfections are compensated using a transformation matrix spectral retrieval algorithm. In a typical configuration, a waveguide array of MachZehnder interferometers (MZIs) with increasing path differences are used to implement the SHS concept [9,10]. For such a geometry, the source power spectrum and the output interferogram are related by the cosine FT. A similar MZI array geometry, including phase-correction circuits using independent heaters for each MZI, has also been demonstrated [13].…”

“…Étendue is of critical importance for spectroscopy applications, especially when spatially extended and incoherent sources are analyzed. This limitation can be overcome with planar waveguide Fouriertransform (FT) spectrometers [9,10] based on the principle of spatial heterodyne spectroscopy (SHS) [11]. SHS benefits from the intrinsically large étendue of the Michelson interferometer [12] and replaces the moving mirrors by stationary diffraction gratings [11].…”

“…SHS benefits from the intrinsically large étendue of the Michelson interferometer [12] and replaces the moving mirrors by stationary diffraction gratings [11]. In a planar waveguide SHS FT spectrometer, all the outputs of the device, corresponding to different optical path lengths of the interferometer array, are monitored simultaneously in a single measurement of the output spatial interferogram [9,10]. The source spectrum can be retrieved by mathematical analysis of the interferogram.…”