Microsphere lasers operating at the
$2\;{\text{μ}}{\rm{m}}$
band have important applications in the fields of bio-medical sensing, laser radars, narrow linewidth optical filtering, and air-pollution monitoring. In this work, we utilize a novel type of chalcogenide glass, whose composition is Ge-Ga-Sb-S or 2S2G, to fabricate microsphere lasers. Compared with chalcogenide glasses used in previous microsphere lasers, this 2S2G glass is environmentally friendly. It also has a lower melting temperature and a higher characterization temperature, implying that 2S2G microspheres can be fabricated at lower temperatures and the crystallization problem happening in the sphere-forming process can be mitigated. A
$\text{Tm}^{3+}\text{-}\text{Ho}^{3+} $
co-doping scheme is applied to the 2S2G glass, so that fluorescence light at ～
$2\;{\text{μ}}{\rm{m}}$
can be obtained from the bulk glass. Owing to the superior properties of the 2S2G glass, we can utilize a droplet method to mass-produce hundreds of high-quality 2S2S microspheres in one experimental run. The diameters of microspheres fabricated in this work fall in a range of 50−
$250\;{\text{μ}}{\rm{m}}$
and typical quality factors (
Qfactor) of microspheres are higher than 10
5. As a representative example, we characterize the optical properties of a
$205.82\;{\text{μ}}{\rm{m}}$
diameter 2S2G microsphere. This microsphere is placed in contact with a silica fiber taper, so that the pump light can be evanescently introduced into the microsphere and the fluorescence light can be evanescently collected from the microsphere. A commercial laser diode (808 nm) is used as a pump source and an optical spectral analyzer is used to measure the transmission spectra of the microsphere/fiber taper coupling system. Apparent whispering gallery mode patterns in the ～
$2\;{\text{μ}}{\rm{m}}$
band can be noted in the transmission spectra of the coupling system. When the pump power increases beyond a threshold of 0.848 mW, a lasing peak at 2080.54 nm can be obtained from the coupling system. Experimental results presented in this work show that this 2S2G chalcogenide glass is a promising base material for fabricating various active optical/photonic devices in the middle-wavelength and long-wavelength infrared spectra.
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