Understanding the fiber tip thermal runaway present in 3 µm fluoride glass fiber lasers.

When the tip of a fluoride glass fiber is exposed to ambient air, water vapor reacts with the glass constituents, increasing the OH contaminants at the surface. These OH impurities then diffuse inside the glass according to Fick's laws. Laser radiation at around 3 µm is strongly absorbed by the OH contaminants, causing local heating of the fiber tip resulting in an increase of the diffusion process which ultimately leads to fiber tip destruction. We accurately model this phenomenon by combining the diffusion theory with a basic thermal equation. Experimental measurements are in agreement with the model predictions for a good range of operating conditions.

3.7 W fluoride glass Raman fiber laser operating at 2231 nm.

The first demonstration of a multi-watt continuous wave fluoride glass Raman fiber laser operating beyond 2.2 µm is reported. A maximum output power of 3.7 W was obtained from a nested cavity setup with a laser slope efficiency of 15% with respect to the launched pump power.

20 W passively cooled single-mode all-fiber laser at 2.8 µm.

A maximum output power of 20.6 W at 2.825 µm from an erbium-doped all-fiber laser is reported, which we believe is the highest output power for this laser transition in single-mode operation. The slope efficiency of the passively cooled laser was up to 35.4% with respect to the absorbed pump power. Accounting for an estimated round-trip intracavity loss of 1.3 dB, we calculated a theoretical conversion efficiency of 39.5%, which is 15% higher than the Stokes efficiency of 34.3%. We believe this is the first experimental confirmation of the predicted pump energy recycling for this fiber laser. The narrow laser linewidth varied from 0.09 to 0.16 nm from low to maximum output power.

Highly stable and efficient erbium-doped 2.8 microm all fiber laser.

We demonstrate the efficient and stable CW laser operation at 2.824 microm of a diode-pumped erbium-doped fluoride fiber laser employing an intracore fiber Bragg grating high reflector. An output power of 5 W and an optical-to-optical conversion efficiency of 32% are reported. The temporal and spectral stability of the laser represent a significant improvement over previous work. This report paves the way to the commercialization of compact and stable fiber lasers for spectroscopic and medical applications.

Erbium-doped all-fiber laser at 2.94 microm.

We report what we believe is the first demonstration of laser emission at 2.94 microm in an erbium-doped fluoride fiber laser. The low-loss all-fiber Fabry-Perot laser cavity was formed by two fiber Bragg gratings of 90% and 15% reflectivities in a 6.6 m, 7 mol.% Er-doped double-clad fiber. A maximum cw output power of 5.2 W was measured, which is to our knowledge the highest reported to date for a diode-pumped laser at this wavelength. A coreless endcap was fused at the output fiber end to prevent its deterioration at high output powers. Our results, including the slope efficiency of 26.6% with respect to launched pump power, suggest that erbium could be a better alternative than holmium in the search for a replacement for the flashlamp-pumped Er:YAG at 2.94 microm.

High power handling shape memory alloy optical fiber connector.

We present a novel shape memory alloy-based optical fiber splicing device that can provide robust, low loss, and high power handling splices between single-mode fibers of identical or entirely different glass compositions. The achieved splice loss was as low as 0.12 dB between two SMF-28 fibers with an average value of 0.23 dB. To the best of our knowledge, this is the first demonstration of a purely mechanical splicing device that can withstand optical powers in excess of 10 W with various combinations of silica and fluoride fibers. The device can be used in moderate to high power all-fiber components, especially those involving junctions unsuitable to fusion splicing, such as fiber lasers and amplifiers based on fluoride, chalcogenide, or microstructured fibers.

Monolithic fluoride-fiber laser at 1480 nm using fiber Bragg gratings.

We report what we believe is the first monolithic fluoride-fiber laser making use of fiber Bragg gratings written directly in the doped fluoride-fiber core. The Tm(3+):ZBLAN fiber laser is upconversion pumped at 1070 nm and emits at 1480 nm. Using two different all-fiber cavities, we observed a threshold as low as 75 mW and a conversion efficiency of up to 40% with respect to launched pump power.