Power scaling of narrow-linewidth mid-IR spherical microlasers

Abstract

We discuss issues re: power scaling of mid-IR Er:ZBLAN spherical microlasers and demonstrate achievement of near-milliwatt power levels from a narrow-linewidth (Δλ < 50 pm) 2.71 µm laser source based on an Er:ZBLAN microlaser.Narrow linewidth mid-infrared (MIR) lasers are important sources for trace level detection of a broad range of molecular species by spectroscopic methods [1,2]. For this application, interband and quantum cascade semiconductor lasers (ICLs and QCLs) --of distributed feedback (DFB) design [3,4] --are currently the most readily available compact sources of narrow-linewidth mid-IR emission (Δν < 30 MHz). However, the complexity of the growth and fabrication process of these semiconductor lasers makes them relatively expensive, particularly when different designs are needed in small quantities. Moreover, since the circulating optical power is not easily accessible in ICLs and QCLs, these lasers are not easily adaptable for ultrahigh-sensitivity intracavity molecular detection. In addition, the 2.7 -2.8 µm MIR spectral range for high-sensitivity molecular detection application of several important molecular species (such as H 2 O, CO 2 , HF, HOCL) is not easily achievable by narrow linewidth ICLs or QCLs [3,4].Glass-based whispering gallery mode lasers (WGMLs) are alternative compact sources of narrow linewidth NIR [5,6] and MIR radiation [7,8,9] that are not only highly amenable for intracavity sensing applications (because of the extension of the evanescent tail into the surrounding analyte-bearing medium), but also readily lend themselves to much simpler fabrication processes [5-10], largely because high quality factor ("high-Q") glass WGML microspheres of variable dimensions are relatively easy to fabricate individually, and the doped-glass gain medium also serves as the laser cavity without the need for any external mirror or feedback

Fabrication and characterization of Ge–Ga–Sb–S glass microsphere lasers operating at $\sim 1.9\,{\rm{\mu }}{\rm{m}}$

“…[6] Behzadi et al reported a 2.71-µm microsphere laser based on an Er 3+ -doped ZBLAN glass. [7][8][9] Chalcogenide glasses are also promising base materials for MIR microsphere lasers. [10] Compared to the tellurite and ZBLAN glasses, chalcogenide glasses have much wider transmission windows and thus can potentially support more operation wavelengths for microsphere lasers.…”