Integrated spectrometers on the basis of AWGs and photonic Echelle gratings are important instruments for airborne and spaceborne spectroscopic surveys, where low weight, small dimensions and mechanical robustness are essential features.
At innoFSPEC, spectrometers based on planar lightwave circuits (PLC) are being developed. The device, “arrayed waveguide grating (AWG)”, was originally introduced in optical communications as wavelength (de)multiplexers. For astronomical applications such devices have to be improved to an unprecedented level. Cooperation with established foundry has yielded a device with the state-of-the-art performance: high spectral resolution, high throughput, broad free spectral range, high polarization immunity and high temperature stability.
Other key components such as filter elements, combiners / splitters, interferometers and high-Q resonators can be integrated on the same chip for light-path routing, amplitude / phase mixing and wavelength self-referencing. The concept “astronomy-on-chip” may spark a paradigm shift in the astronomical instrumentation as the light-weight PLC-based devices can provide simultaneously superior functionalities and greater robustness. A packaged module further allows efficient thermal management and shielding against external disturbances. The plug-and-play deployment may tremendously reduce the system maintenance cost, a “dream instrument” for observational astronomers.
The first generation of fabricated AWGs have very high throughputs, an important feature for “astronomy-on-chip” and do not require any post-processing. Currently a compact spectrometer is being developed incorporating the AWGs. Further research is being conducted on photonic Echelle grating designs which are optimized specifically for spectroscopic applications.