Ultrafast laser-inscribed mid-infrared transmission gratings in IG2: modelling and high-resolution spectral characterization

The ultrafast laser inscription technique was used to fabricate mid-infrared volume gratings in the bulk of chalcogenide glass IG2 (Ge33As12Se55). These gratings are spectrally characterized using a Fourier transform infrared spectrometer, by measuring the transmission spectrum over the entire transmission band of the IG2 substrate. The gratings exhibit first order diffraction across the entire 2-5 mu m spectral band, with the specific transmission band tuned by changing the angle of incidence. Higher diffraction orders are also observed. High-resolution spectral data is presented alongside detailed modelling and analysis. This work provides the basis for future design of mid-infrared transmission gratings; ULI provides a low-cost, robust alternative to mid-infrared reflection gratings, with the added capability to engineer the grating response to a specific application. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License.