Due to their high efficiency and broad operational bandwidths, volume phase holographic gratings (VPHGs) are often the grating technology of choice for astronomical instruments, but current VPHGs exhibit a number of drawbacks including limits on their size, function and durability due to the manufacturing process. VPHGs are also generally made using a dichromated gelatine substrate, which exhibits reduced transmission at wavelengths longer than similar to 2.2 mu m, limiting their ability to operate further into the mid-infrared.
An emerging alternative method of manufacturing volume gratings is ultrafast laser inscription (ULI). This technique uses focused ultrashort laser pulses to induce a localised refractive index modification inside the bulk of a substrate material. We have recently demonstrated that ULI can be used to create volume gratings for operation in the visible, near-infrared and mid-infrared regions by inscribing volume gratings in a chalcogenide glass. The direct-write nature of ULI may then facilitate the fabrication of gratings which are not restricted in terms of their size and grating profile, as is currently the case with gelatine based VPHGs.
In this paper, we present our work on the manufacture of volume gratings in gallium lanthanum sulphide (GLS) chalcogenide glass. The gratings are aimed at efficient operation at wavelengths around 1 mu m, and the effect of applying an anti-reflection coating to the substrate to reduce Fresnel reflections is studied.
|Title of host publication||Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation|
|Editors||R Navarro, CR Cunningham, AA Barto|
|Place of Publication||Bellingham|
|Number of pages||6|
|Publication status||Published - 2014|
|Event||Conference on Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation - Montreal, Canada|
Duration: 23 Jun 2014 → 27 Jun 2014
|Name||Proceedings of SPIE|
|Conference||Conference on Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation|
|Period||23/06/14 → 27/06/14|
- Diffraction grating
- volume phase holographic gratings
- ultrafast laser inscription
- FEMTOSECOND LASER