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Proceedings Paper

Mid-infrared volume diffraction gratings in IG2 chalcogenide glass: fabrication, characterization, and theoretical verification
Author(s): Helen L. Butcher; David G. MacLachlan; David Lee; Richard A. Brownsword; Robert R. Thomson; Damien Weidmann
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Paper Abstract

Ultrafast laser inscription (ULI) has previously been employed to fabricate volume diffraction gratings in chalcogenide glasses, which operate in transmission mode in the mid-infrared spectral region. Prior gratings were manufactured for applications in astrophotonics, at wavelengths around 2.5 μm. Rugged volume gratings also have potential use in remote atmospheric sensing and molecular spectroscopy; for these applications, longer wavelength operation is required to coincide with atmospheric transparency windows (3-5 μm) and intense ro-vibrational molecular absorption bands. We report on ULI gratings inscribed in IG2 chalcogenide glass, enabling access to the full 3-5 μm window. High-resolution broadband spectral characterization of fabricated gratings was performed using a Fourier transform spectrometer. The zeroth order transmission was characterized to derive the diffraction efficiency into higher orders, up to the fourth orders in the case of gratings optimized for first order diffraction at 3 μm. The outcomes imply that ULI in IG2 is well suited for the fabrication of volume gratings in the mid infrared, providing the impact of the ULI fabrication parameters on the grating properties are well understood. To develop this understanding, grating modeling was conducted. Parameters studied include grating thickness, refractive index modification, and aspect ratio of the modulation achieved by ULI. Knowledge of the contribution and sensitivity of these parameters was used to inform the design of a 4.3 μm grating expected to achieve > 95% first order efficiency. We will also present the characterization of these latest mid-infrared diffraction gratings in IG2.

Paper Details

Date Published: 22 February 2018
PDF: 6 pages
Proc. SPIE 10528, Optical Components and Materials XV, 105280R (22 February 2018); doi: 10.1117/12.2288357
Show Author Affiliations
Helen L. Butcher, STFC Rutherford Appleton Lab. (United Kingdom)
David G. MacLachlan, Heriot-Watt Univ. (United Kingdom)
David Lee, UK Astronomy Technology Ctr. (United Kingdom)
Richard A. Brownsword, STFC Rutherford Appleton Lab. (United Kingdom)
Robert R. Thomson, Heriot-Watt Univ. (United Kingdom)
Damien Weidmann, STFC Rutherford Appleton Lab. (United Kingdom)

Published in SPIE Proceedings Vol. 10528:
Optical Components and Materials XV
Shibin Jiang; Michel J. F. Digonnet, Editor(s)

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