Compact Hundred-mW $2~\mu \text{m}$ Single-Frequency Thulium-Doped Silica Fiber Laser

Single-frequency distributed Bragg reflector Tm:YAG ceramic derived all-glass fiber laser at 1.95 μm

“…[7] The output power of a 2 µm single-frequency DBR fiber laser can be improved by means of in-band pumping at the 1.5 µm band. [15] Note that multicomponent glasses, which have high RE ion solubility, are usually used to fabricate high-gain glass fibers. [1,16] Geng et al reported a single-frequency DBR fiber laser at 1893 nm based on a 2 cm long heavily Tm 3+ -doped germanate glass fiber; this had a pump threshold of 30 mW and a maximum output power of 50 mW.…”

“…[12] However, the large splicing losses (∼ 2.2 dB) between the active fiber and two FBGs resulted in a relatively high threshold. [12,15] In 2018, Tang et al fabricated a heavily Tm 3+ -doped barium gallo-germanate glass fiber that had a gain per unit length of 3.6 dB•cm −1 at 1.95 µm. [13] A singlefrequency DBR fiber laser of over 220 mW at 1.95 µm was realized in a 1.5 cm long active fiber, showing a slope efficiency of 30.2% with respect to the absorbed pump of a 1568 nm fiber laser.…”

“…[13] Although the multicomponent glass fibers used in these reports possess higher RE ion solubility over the silica fiber, which enables ∼ 2 µm single-frequency DBR fiber laser operation with higher output power and slope efficiency, there are still some obstacles to their application in the aforementioned areas. [15,18] For example, their softening temperature and thermal expansion coefficient are different from those of commercial silica glass fiber, implying that it is more challenging to achieve low-loss spliced with silica-based fiber devices, such as wavelength division multiplexer (WDM) and FBG. [7] Moreover, the resulting splice joint exhibits reduced mechanical strength, which sacrifices the reliability of the fiber laser system.…”

Power scaling and spectral linewidth suppression of hybrid Brillouin/thulium fiber laser

“…A cladding mode striper (CMS) was employed to strip the residual 793-nm pump power and it was cooled by water cooled heat sink to alleviate the linewidth broadening induced by thermal load. The active fiber has a core pump absorption coefficient at 1570 nm of 250 dB/m and a cladding pump absorption coefficient at 793 nm of 4.7 dB/m, respectively [33,34]. All the fiber and devices employed in the experiment were polarization-maintaining.…”

Tm3+-doped barium gallo-germanate glass single-mode fiber with high gain per unit length for ultracompact 1.95 µm laser

“…Up to now, single-frequency fiber lasers at ∼2 µm have been implemented with different Tm 3+ -doped glass fibers, such as silica, silicate, and germanate glass fibers. [13][14][15] Nevertheless, the Tm 3+ doping concentration is restricted in silica glass due to its well-defined glass network, which means that Tm 3+ -doped silica fibers with high gain per unit length are not achievable. Silicate glass and germanate glass, two subfamilies of multicomponent glasses, have recently emerged as potential host materials owing to their higher Tm 3+ ion solubility than that of silica glass.…”