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First demonstrated over four decades ago, fiber gratings, and in particular fiber Bragg gratings (FBGs), have become indispensable and ubiquitous components within fiber laser cavities as well as optical communication networks and sensor systems. Because of their overwhelming use, the bulk of published work to date has concentrated on fibers that are composed of silica-based glasses, yet those become virtually opaque at wavelengths above 2 μm, i.e., in the technically increasingly important mid-infrared part of the electromagnetic spectrum. Soft glass fluoride fibers on the other hand, in particular those composed of ZBLAN (abbreviation for ZrF4-BaF2-LaF3-AlF3-NaF), offer low-loss transmission out to wavelengths of up to almost 4 μm. However, while fiber manufacturing itself has now reached a high level of maturity, with passive fiber attenuation levels as low as 1 dB/km becoming commercially available, grating fabrication in these fibers remains challenging, and research into suitable inscription techniques is still a very active and ongoing scientific field. This review aims to provide an overview of work that has been done in this area to date with an emphasis on femtosecond-laser based fabrication methods.

We present numerical modeling of mid-infrared (MIR) supercontinuum generation (SCG) in dispersion-optimized chalcogenide (CHALC) step-index fibres (SIFs) with exceptionally high numerical aperture (NA) around one, pumped with mode-locked praseodymium-doped (Pr3+) chalcogenide fibre lasers. The 4.5um laser is assumed to have a repetition rate of 4MHz with 50ps long pulses having a peak power of 4.7kW. A thorough fibre design optimisation was conducted using measured material dispersion (As-Se/Ge-As-Se) and measured fibre loss obtained in fabricated fibre of the same materials. The loss was below 2.5dB/m in the 3.3-9.4μ m region. Fibres with 8 and 10μm core diameters generated an SC out to 12.5 and 10.7μm in less than 2m of fibre when pumped with 0.75 and 1kW, respectively. Larger core fibres with 20μm core diameters for potential higher power handling generated an SC out to 10.6μm for the highest NA considered but required pumping at 4.7kW as well as up to 3m of fibre to compensate for the lower nonlinearities. The amount of power converted into the 8-10 μm band was 7.5 and 8.8mW for the 8 and 10μm fibres, respectively. For the 20μm core fibres up to 46mW was converted.

We theoretically demonstrate a novel approach for generating Mid-InfraRed SuperContinuum (MIR SC) by using concatenated fluoride and chalcogenide glass fibers pumped with a standard pulsed Thulium (Tm) laser (TFWHM=3.5ps, P0=20kW, νR=30MHz, and Pavg=2W). The fluoride fiber SC is generated in 10m of ZBLAN spanning the 0.9–4.1μm SC at the −30dB level. The ZBLAN fiber SC is then coupled into 10cm of As2Se3 chalcogenide Microstructured Optical Fiber (MOF) designed to have a zero-dispersion wavelength (λZDW) significantly below the 4.1μm InfraRed (IR) edge of the ZBLAN fiber SC, here 3.55μm. This allows the MIR solitons in the ZBLAN fiber SC to couple into anomalous dispersion in the chalcogenide fiber and further redshift out to the fiber loss edge at around 9μm. The final 0.9–9μm SC covers over 3 octaves in the MIR with around 15mW of power converted into the 6–9μm range.

SPIRou is a near-IR (0.98-2.35μm), echelle spectropolarimeter / high precision velocimeter being designed as a next-generation instrument for the 3.6m Canada-France-Hawaii Telescope on Mauna Kea, Hawaii, with the main goal of detecting Earth-like planets around low mass stars and magnetic fields of forming stars. The unique scientific and technical capabilities of SPIRou are described in a series of seven companion papers. In this paper, the fiber links which connects the polarimeter unit to the cryogenic spectrograph unit (35 meter apart) are described. The pupil slicer which forms a slit compatible with the spectrograph entrance specifications is also discussed in this paper. Some challenging aspects are presented. In particular this paper will focus on the manufacturing of 35 meter fibers with a very low loss attenuation (< 13dB/km) in the non-usual fiber spectral domain from 0.98 μm to 2.35 μm. Other aspects as the scrambling performance of the fiber links to reach high accuracy radial velocity measurements (1m/s) and the design of the pupil slicer exposed at a cryogenic and vacuum environment will be discussed., Ground-Based and Airborne Instrumentation for Astronomy IV, July 1-6, 2012, Amsterdam, Netherlands, Series: Proceedings of SPIE