Planar integrated photonics spectrograph on silicon-nitride-on-insulator: densely integrated systems for astrophotonics and spectroscopy

摘要

A conventional Arrayed Waveguide Grating (AWG) has been modified, without output receiver waveguides, for nonconventionalapplications such as Astrophotonics and spectroscopy sensing where the input signal can have informationover the entire band and a continuum of light/spectrum. The material system chosen for the AWG design is siliconnitride/SiOsub2/sub/Si (Sisub3/subNsub4/sub-SiOsub2/sub-Si) for its relatively high refractive index, which for a given channel spacing allowing amore compact device than Silicon-on-Silica. Further, CMOS compatibility and the presence of high non-liner opticalcoefficient would be an added advantage to design and fabricate densely integrated photonic sub-systems, such ascalibration source and AWG, for astrophotonics and spectroscopy. The proposed AWG utilizes a flat image planeoptimized for minimal aberration. An analytical calculation, based on Gaussian beam approximation, was used todetermine the optimal flat plane position where the non-uniformity in 1/e electric field widths is minimal. This plane canbe used as the dicing plane to re-image the entire output of the AWG onto a detector array to sample the entire spectrum.Tailored AWG, with flat image-plane, designed to resolve 48 spectral channels with 0.4nm (50GHz) resolution andadjacent channel cross-talk level within a 0.2nm window (ITU-grid) ~ -28dB. Calculated insertion loss non-uniformity isclose to 3dB. The foot-print of high index contrast (Δn=23%) IPS is ~ 12x8.5 mmsup2/sup. The modelled mean spectralresolving power, R, at the flat image-plane is ~ 7,600. The design principle could be utilised for devices using othermaterial systems with different parameters.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.