The LD-clad-pumped CW and Q-switched pulse Tm<sup>3+</sup>-doped silica fiber amplifiers were general experimental
investigations. The CW fiber amplifier provided up to 3W output with the slope efficiency nearly 30%, and the Q-switched
pulse fiber amplifier output power was 2W with the slope efficiency 32.6%. The gain fiber was 27.5/400μm D-shaped
Tm<sup>3+</sup>-doped silica double-cladding fiber, and the pump sources was a 792nm LD with a 400μm pigtail fiber
output. The signal seed sources was a LD-pumped Tm<sup>3+</sup>:YAP lasing at 1.99μm. By the AO Q-switched method, The
Tm<sup>3+</sup>:YAP laser had a nearly 120ns pulse duration and 1kHz repeat rates. The measured amplified spectrum only
stretched a little relative to the input signal spectrum.
An all-fiber LD-clad-pumped Tm-doped fiber laser was reported, and the CW maximal output power reached 24W at
nearly 1.94µm. The homemade double-clad Tm<sup>3+</sup>-doped fiber had a demission of 25/250µm with the core NA 0.13 and
inner-clad NA 0.46. A matched passive multi-mode FBG acted as the front cavity. The cavity was build-up by the high
reflectivity FBG and fiber end Fresnel reflectivity. The all-fiber scheme was build-up by splicing the pigtail fiber, FBG
fiber and Tm<sup>3+</sup>-doped fiber. Cooling by the water, the 56% high slope efficiency was achieved and threshold was 6.4W,
respected to the launched pump power. When the output power was less-than 3W, the output laser was single-peak
operating at 1936.4 nm with a very narrow linewidth (50 pm) laser output. Increasing the launched pump power, the
output laser wavelength grew to 3~4 peaks. The multimode fiber Bragg grating (FBG) transmission spectrum was also
measured with a matched 82cm Nufern Tm<sup>3+</sup>-doped fiber as fluorescent sources. With the dichroic and the FBG building
up cavity, the output laser characteristics were also investigated. Because the multi-mode FBG reflectivity was not very
high, both ends of the fiber laser had laser output power, and the ratio was nearly 10:1. As we know, it was the first time
to report the multi-mode FBG all-fiber laser. Under this simple Tm<sup>3+</sup>-doped fiber laser scheme, we estimated that the
maximal output power could reach several ten watts.
A gain-switched Tm-doped double-clad silica fiber laser operating at a wavelength of approximately 2μm with moderate output energy is realized. A gain-switched Nd:YAG laser is used to pump the 3 5 H energy level of the doped Tm<sup>3+</sup> ions at 1.064μm, and a maximum total output energy of 14.7mJ per pulse is produced at a slope efficiency of 39.5% (with respect to launched pump energy). As we know, this is the first time to realize the gain-switched Tm<sup>3+</sup>-doped double-clad silica fiber laser pumped at 1.064μm, and both the single pulse energy and the slope efficiency exceed the reported results that produced from single-clad Tm<sup>3+</sup>-doped silica fiber laser in the past. The results of three different length fibers in experiments are present and contrasted. Because the absorption section at 1.064μm is only 2.5% at 0.79 μm in Tm<sup>3+</sup>-doped silica fiber, we use three relative long fibers (the fiber.1 length 35 m, fiber.2 length 8m, the fiber.3 length 1m.) to increase the absorption ratios. The laser threshold in fiber.1, fiber.2 and fiber.3 is 37.5mJ, 39.4mJ and 48 mJ, and the slope efficiency is 39.5%, 11.6% and 1% respectively. The output peak wavelength from fiber.1 fiber.2 and fiber.3 is 2.04μm, 2.01μm and 1.92μm measured by a monochromator respectively.