We present development of a nanosecond Q-switched Tm<sup>3+</sup>-doped fiber laser with 16 W average power and 4.4 kW peak power operating at 1940 nm. The laser has a master oscillator power amplifier design, and uses large mode area Tm<sup>3+</sup>-doped fibers as the gain medium. Special techniques are used to splice Tm<sup>3+</sup>-doped fibers to minimize splice loss. The laser design is optimized to reduce non-linear effects, including modulation instability. Pulse width broadening due to high gain is observed and studied in detail. Medical surgery is a field of application where this laser may be able to improve clinical practice. The laser together with scanning galvanometer mirrors is used to cut precisely around small footprint vessels in tissue phantoms without leaving any visible residual thermal damage. These experiments provide proof-of-principle that this laser has promising potential in the laser surgery application space.
We discuss second harmonic generation of green and blue light in periodically-poled LiNbO3 and LiTaO3 waveguides, and difference frequency generation of infrared radiation in periodically-poled LiNbO3 waveguides.