Pal, Atasi and Chen, Shu Ying and Sen, Ranjan and Sun, Tong and Grattan, K T V (2013) A high-Q low threshold thulium-doped silica microsphere laser in the 2 mu m wavelength region designed for gas sensing applications. Laser Physics Letters, 10 (8). Article No. ISSN 1612-202X

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Abstract

A high-Q and low threshold laser resonator, operating in the 2 mu m wavelength region, has been demonstrated by coupling a thulium-doped silica microsphere to a tapered fibre. Microspheres with diameters ranging from fifty to a few hundred micrometres were carefully fabricated for this purpose by melting an etched-clad thulium-doped silica fibre tip using a focused beam from a CO2 laser, while the tapered fibre with waist diameter in the desired range of 2 mu m was fabricated by using heating and stretching of standard single-mode telecommunication fibre. The tapered fibre served the dual purpose of transporting pump power into the sphere and allowing the extraction of the resulting laser emission. Under excitation at a wavelength of similar to 1.6 mu m, lasing occurred at wavelengths over the range from 1.9 to 2.0 mu m. Single-mode laser operation was obtained by exciting the fundamental whispering gallery mode resonance of the microsphere, while multi-mode lasing occurred for non-fundamental mode excitation. The threshold power of the laser was measured to be about 50 mu W delivered pump power, and a maximum laser power of 0.8 mW at around 1.94 mu m was observed for a 6 mW pump power, operating at wavelengths around 1.6 mu m. The laser was designed as a low threshold and compact source for miniaturized gas sensing devices operating over this important wavelength region.

Item Type:	Article
Subjects:	Processing Science
Divisions:	Fiber Optics and Photonics
Depositing User:	Bidhan Chaudhuri
Date Deposited:	06 Feb 2014 08:29
Last Modified:	12 Mar 2016 15:55
URI:	http://cgcri.csircentral.net/id/eprint/2490

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