140 W Cr:ZnSe laser system

Abstract

We report a significant breakthrough in the development of fiber-pumped high-power CW laser systems based on Cr²⁺:ZnS and Cr²⁺:ZnSe gain media. We demonstrate output power levels of up to 140 W near 2500 nm, and 32 W at 2940 nm with corresponding optical efficiencies of 62% and 29%. Our novel approach is based on rapid simultaneous scanning of the collinear laser mode and pump beam across the Cr:ZnS/Se gain element which allows us to virtually eliminate thermal lensing effects and obtain unprecedented levels of output power with very high optical-to-optical efficiency.

Design of a new family of narrow-linewidth mid-infrared lasers

“…There are clearly a broad diversity of high power broadband MIR pump sources cited in the literature [66][67][68], and most of these can be used with appropriate beam shaping and fiber coupling lens assemblies as pumps for the proposed RFLs, particularly since the pump bandwidth requirements are relatively flexible (bandwidths as large as a few nm are acceptable without significant loss in conversion efficiency due to the large Raman gain bandwidths of the glasses used). Nevertheless, for simplicity we focus here first on the possible spectral coverage that may be achievable with the use of demonstrated and easily-buildable fiber lasers of pulse durations longer than about 10 ns (depending on the DFB length, to justify the steady-state analysis requirement and enable sufficient reduction in the linewidth), including 2 µm Tm:SiO2 FLs [69], 3 µm Er: ZBLAN FLs [23,24,70] and conventional "broadband" cascaded fiber Raman lasers [21,71].…”

“…10, ie, n = 3) outcouples with an appropriately high coupling efficiency to generate a high power pump source at λs,n, with a power conversion efficiency limited primarily by the quantum deficit between the original MIR FL pump and the final Stokes wavelength. With the use of higher power pumps (for instance, see [68]), large Stokes shift broadband tellurite RFL-based pumps, and a larger number (n > 6) of "nested" cascaded RFL pumps [18,22], this nested RFL-based concept is easily extendible to NLW sources upto 10 µm or so, limited only by the availability of smallmode-area chalcogenide fibers with sufficiently high nonlinearities and transparencies. This pump scheme is particularly important if one needs to extend the narrow linewidth RFL source to specific target long MIR wavelengths such as those corresponding to specific absorption lines in target molecules for trace or remote detection systems.…”

Direct bonding diamond to zinc selenide

“…Zinc selenide (ZnSe) has been demonstrated as an excellent host medium for use in mid-infrared laser operation when doped with chromium or iron [5]. Recent advances have pushed laser output powers to 140W in a disk architecture, but significant efforts are required to mitigate the strong thermal lensing effects [6] that arise from ZnSe's high thermo-optical coefficient ( dn dT ) of 70 × 10 −6 K −1 [4]. In contrast to diamond, ZnSe suffers from an extremely low mechanical hardness (Knoop 120, compared with diamond's Knoop 5,700-10,400) and has significantly lower thermal conductivity (18Wm −1 K −1 @298K) [4].…”

Broadband mid‐infrared emission from Cr2+ in crystal‐in‐glass composite glasses by Hot Uniaxial Pressing

“…Cr 2+ can be stably present in tetrahedral coordinated ZnSe crystals to produce an effectively tunable MIR laser, but it is impossible in chalcogenide glasses. 10 Although, Cr 2+ :ZnSe crystals have made considerable progress in solid-state MIR laser technology, 11 few ideal results have been obtained for the preparation of fiber geometry after years of research. 10 Although, Cr 2+ :ZnSe crystals have made considerable progress in solid-state MIR laser technology, 11 few ideal results have been obtained for the preparation of fiber geometry after years of research.…”

“…9 Its emission band covers a range of 1.9-3.1 μm and has great applications. 10 Although, Cr 2+ :ZnSe crystals have made considerable progress in solid-state MIR laser technology, 11 few ideal results have been obtained for the preparation of fiber geometry after years of research. However, the breakthrough contributions made by researchers in this field cannot be ignored.…”