ABSTRACT
We used guided-mode resonance filters (GMRFs), fabricated using thin-film deposition and chemical etching, as intracavity feedback elements to stabilize and narrow the output spectrum in thulium-doped fiber oscillators operating in the 2 µm wavelength regime, producing linewidths of <700 pm up to 10 W power levels. A Tm fiber-based amplified spontaneous emission source was used to characterize the reflective properties of the GMRFs. Linewidths of 500 pm and a 7.3 dB reduction in transmission were measured on resonances.
ABSTRACT
Applications requiring long-range atmospheric propagation are driving the development of high-power thulium fiber lasers. We report on the performance of two different laser configurations for high-power tunable thulium fiber lasers: one is a single oscillator utilizing a volume Bragg grating for wavelength stabilization; the other is a master oscillator power amplifier system with the oscillator stabilized and made tunable by a diffraction grating. Each configuration provides >150 W of average power, >50% slope efficiency, narrow output linewidth, and >100 nm tunability in the wavelength range around 2 µm.
ABSTRACT
A Tm-doped large mode area (LMA) silica fiber laser has been locked to a stable wavelength of 2,053.9 nm using a volume Bragg grating (VBG). The measured spectral width of the laser output was <300 pm, limited by the spectrometer resolution. Although this laser had modest output (approximately 5W) and slope efficiency (41%), this new approach to spectrally limiting the output of LMA fiber lasers is inherently extendable to kilowatt powers, opening up several applications including high-power pulsed fiber lasers and spectral beam combining. Performance characteristics of the laser compared to one using a dielectric mirror as a high reflector are described, and the results imply low VBG losses.
ABSTRACT
Lowest-order, single-mode laser oscillation is reported in gain-guided index-antiguided fiber lasers having core diameters from 100 to 400 microm. A model is presented explaining how to select resonator mirrors to assure single-mode operation.
