New Architectures for intense middle infrared lasers – ArchiMid

The whole range of the electromagnetic spectrum gives access to a wide variety of characterization and imaging techniques to study the physical and chemical properties of matter at different size and timescales. But due to the lack of suitable lasers sources or efficient detectors, the entire range is not covered. The middle infrared (midIR) remains one of the last frontier between 2 and 8 µm, where ultrashort, intense and coherent sources are not optimized.
Yet, the development of broadband, widely tunable and intense midIR sources in the 2-12 µm is of great importance not only for basic research but also for applications in medicine, defense and security in band I (0,5-2,5 µm), II (3-5,5 µm). Depending on the targeted application, a greater emphasis is given to the high energy, the bandwidth or the tunability: since midIR spans over most of the vibrational and rotational spectra of molecules, it is well-suited for hyperspectral imaging, or atmospheric gas sensing with LIDAR.
Nevertheless, the rarity of midIR-emitting lasers material makes it difficult to efficiently produce ultrashort lasers in this range. To reach this frequency domain, the available near infrared lasers (Ti:Sa, Yb) are converted with non-linear techniques. However, these methods suffers from limitations due to the strong midIR absorption of the common crystals, the high pump absorption by the crystals transparent in the midIR (AgGaS2 and other chalcogenides, ZGP, CSP) pumped with near infrared laser, and the multiphoton absorption of the pump at wavelength < 1µm. Moreover, several applications such as LIDAR simultaneously require high energy par pulse, high average power, high repetition rates (multi-kHz) in order to obtain a good signal-to-noise ratio.
In order to circumvent these limitations, and to meet the requirement for an efficient generation of midIR radiation, it is necessary to develop an intense pico- to sub-picosecond multi-kHz pump laser emitting at 2µm. Subsequent nonlinear frequency conversion is performed in high-damage-threshold crystals transparent both at 2 µm and at midIR frequencies, and with broad and loosely constraint phase-matching in the 3 – 5 µm range pumped when at 2 µm.
The aim of ArchiMid project is to address the challenges raised the efficient generation of midIR radiation in the 2-5 µm range. The ultrafast lasers and optics group of CELIA laboratory (UMR5107) and the ISL (French-German Research Institute of Saint-Louis) propose to develop a source based on the amplification in Holmium doped materials.
We first aim at producing a novel intense (10 mJ) high-repetion-rate (> 1 kHz) subpicosecond source emitting at 2 µm. Its hybrid fiber-solid architecture is compact and robust, and suitable for integration. These features are of high interest for both academic and industrial applications. The energy will be further increased up to 30-40 mJ, adapted for the generation of intense secondary radiations with with both civil and defense applications. It is particularly well suited for XUV generation up to keV energy, but also for efficient pumping generation of an exceptionally large range midIR wavelengths via optical parametric amplification in nonlinear crystals. Depending on the application (civil or defense), either an intense ultrashort (few cycle) radiation, or an ultrabroad bandwidth (1 to 3 octaves), or else a broadly tunable narrowband spectrum will cover midIR band II.