Continuous-wave cascaded second Stokes diamond Raman laser at 1477 nm.

We report a high brightness cascaded Stokes diamond Raman laser with a diffraction limited beam quality pumped by an Yd-doped fiber laser. The Raman laser operated at 1477 nm and reached an output power of 63 W with 214 W pump power in continuous-wave mode. Conversion efficiency over 30% was achieved using a single pump pass concentric cavity that was highly resonant at the first Stokes and had high outcoupling at the second Stokes (45%).

Diamond Raman oscillator operating at 1178 nm.

In this contribution, we report high-power Raman frequency downconversion based on an Yb-doped fiber amplifier and a linear external diamond Raman cavity. A maximum output power of 136 W with nearly diffraction-limited beam quality was achieved by pumping in quasi-continuous-wave mode with 10% duty cycle and 10 ms on-time duration. For continuous-wave operation, we achieved record average power of 46 W centered at 1178 nm.

Ring-up-doped fiber for the generation of more than 600 W single-mode narrow-band output at 1018 nm.

We present the amplification of a narrow-bandwidth signal at a wavelength of 1018 nm to a power exceeding 600 W with a stable output polarization state. The beam showed an excellent, nearly diffraction-limited beam quality. The high-power output could be realized using an in-house designed and fabricated fiber with a core-cladding diameter ratio of 32/260, ultra-low NA of 0.

Monolithic thulium fiber laser with 567 W output power at 1970 nm.

We report on a monolithic thulium fiber laser with 567 W output power at 1970 nm which, to the best of our knowledge, is the highest power reported so far directly from a thulium oscillator. This is achieved by optimization of the splice parameters for the active fiber (minimizing signal light in the fiber cladding) and direct water cooling. Dual transverse mode operation is visible from the optical spectrum and can be deduced from the measured beam quality of M=2.