Comb-mode-resolving broadband Fourier transform spectroscopy

This report demonstrates progress made to develop a robust turn-key astrocomb architecture for the calibration package of the HIRES spectrograph planned for installation on the upcoming Extremely-Large Telescope (ELT) which intends to enable novel research across a range of scientific disciplines. Here, we demonstrate progress towards a laser frequency comb covering optical and infra-red wavelength ranges and made possible by use of nonlinear interactions driven by a single stabilised mode-locked laser source. We also detail a proof-of-concept experiment carried out with a compact broadband Fourier-transform spectrometer to identify the subset of filtered frequency-comb modes, an important ancillary technology for any future broadband Fabry-P´erot-based astrocomb

Reflecting the past, imag(in)ing the past: macro-reflection imaging of painting materials by fast MIR hyperspectral analysis

Imaging spectroscopy has been developed in the last two decades in the visible and infrared spectral range for detecting pigments and binders on paintings. The near-infrared (NIR) region has been proved effective for the discrimination of lipids and proteinaceous binders. More recently, the mid-infrared (MIR) range has also been tested on paintings. Reflection imaging prototypes already developed could be further optimized for cultural heritage analysis, for example by: enhancing the instrument configuration and performance; adopting compressive strategies to increase data processing speeds; using data validation to confirm that the processed image reflects the composition of a painted surface; and lowering price to enable more cost-effective analysis of large surface areas. Here, we demonstrate a novel hyperspectral Fourier transform spectrometer (HS FTS), which enables an imaging strategy that provides a significant improvement in acquisition rate compared to other state-of-the-art techniques. We demonstrate hyperspectral imaging across the 1400–700 cm−1 region in reflection mode with test samples and the painting ‘Uplands in Lorne’ (Acc. No.: GLAHA43427) by D.Y. Cameron (1865–1945). A post-processing analysis of the resulting hyperspectral images, after validation of reference samples by conventional Fourier transform infrared spectroscopy, shows the potential of the method for efficient non-destructive classification of different materials found on painted cultural heritage. This research demonstrates that the HS FTS is a convenient and compact tool for non-invasive analysis of painted cultural heritage objects at spatio-spectral acquisition rates potentially higher than current FTS imaging techniques. Ultimately, when combined with fast graphics processing unit-based reconstruction, the HS FTS may enable fast, large area imaging

PISTACHIO (Photonic Imaging Strategies For Technical Art History And Conservation)

IR spectral database of artists’ pigments to be used as spectral library for compound identification purposes. Spectra were acquired using a benchtop FTIR microscope in ATR and external reflection, and the novel hyperspectral Fourier-transform spectrometer built within the PISTACHIO project, a collaboration between the University of Glasgow and Heriot-Watt University in Edinburgh