High Power Thulium Fiber Lasers
Abstract
Recent years have seen a phenomenal rise in the capabilities of high power fibers lasers. 10 kW is now achievable in single-mode fiber and the race is on to break the 100 kW mark. This has been enabled with the development of high power 976 nm pump diodes, ideally matched for efficiently exciting the ∼1030-1080 nm transition in Yb-doped silica fibers. In the shadow of this remarkable development we are now witnessing a similar growth pattern for a sister to this laser, the 2 μm thulium fiber laser. This laser possesses rather unique characteristics. Pumped by 790 nm diodes, the excitation scheme uses a cross-relaxation process that results in two-for-one photon generation with slope efficiencies approaching 70%. Powers approaching the kW level are now achievable. This talk summarizes the development of this unique laser source in the MIR, and speculates on its future applications in the medical, manufacturing and defense arenas. In particular we describe new experiments where we exploit the broad >200 nm spectral bandwidth, and the advantages this laser brings to operating in the pulsed regime. We characterize the capabilities of conventional gratings, fiber Bragg gratings, volume Bragg gratings and guided mode resonant filters to lock the linewidth to as small as 50 pm, within the range from ∼1950 nm to ∼2150 nm. This spectral region covers many sharp atmospheric absorption lines in the atmosphere. We describe the first long range (1 km) atmospheric transmission tests with a tunable high power (200 W) thulium fiber laser. The capability to lock a number of these lasers to specific wavelengths each with <100 pm linewidths opens the option of spectrally combining many lasers within the overall spectral bandwidth. We examine the benefits of this approach to reaching 100 kW power levels. In the pulse regime we describe the generation of nanosecond, picosecond and femtosecond pulses in oscillator and MOPA configurations.
- Publication:
-
International Symposium on High Power Laser Ablation 2010
- Pub Date:
- October 2010
- DOI:
- 10.1063/1.3507181
- Bibcode:
- 2010AIPC.1278..852S
- Keywords:
-
- fibre lasers;
- doping profiles;
- Bragg gratings;
- oscillators;
- 42.55.Wd;
- 74.62.Dh;
- 42.79.Dj;
- 42.65.Yj;
- Fiber lasers;
- Effects of crystal defects doping and substitution;
- Gratings;
- Optical parametric oscillators and amplifiers