Tunable fibre Bragg grating arrays for photonic spectral cross-correlation

Photonic platforms and technologies can facilitate the miniaturization of astronomical instruments for high-resolution cross-correlation spectroscopy. Fibre Brag grating (FBG) arrays, inscribed into optical fibres using direct femtosecond laser writing, form a target-tailored instrument spectrum. Flexible modulation of spectral features is provided during instrument operation through strain tuning of the FBG arrays. This paper presents a prototype of an astrophotonic fibre instrument demonstrating cross-correlation spectroscopy for molecular gas absorption in the infrared spectrum. Experimental laboratory results of spectral modulation and cross-correlation analysis are shown to compare well with theoretical models for CO2 gas. Additionally, efforts toward the on-sky integration of the instrument on a 1-meter-class telescope are demonstrated for targeted near-infrared spectral features.