High-power spectral beam combining of linearly polarized Tm:fiber lasers.

To date, high-power scaling of Tm:fiber lasers has been accomplished by maximizing the power from a single fiber aperture. In this work, we investigate power scaling by spectral beam combination of three linearly polarized Tm:fiber MOPA lasers using dielectric mirrors with a steep transition from highly reflective to highly transmissive that enable a minimum wavelength separation of 6 nm between individual laser channels within the wavelength range from 2030 to 2050 nm. Maximum output power is 253 W with M(2)<2, ultimately limited by thermal lensing in the beam combining elements.

High peak-power mid-infrared ZnGeP₂ optical parametric oscillator pumped by a Tm:fiber master oscillator power amplifier system.

We report on the utilization of a novel Tm:fiber laser source for mid-IR ZnGeP2 (ZGP) optical parametric oscillator (OPO) pumping. The pump laser is built in a master oscillator power-amplifier configuration delivering up to 3.36 W of polarized, diffraction limited output power with 7 ns pulse duration and 4 kHz repetition rate.

Amplification of nanosecond pulses to megawatt peak power levels in Tm3+-doped photonic crystal fiber rod.

We report amplification of sub-10-100 ns pulses with repetition rates from 1 to 20 kHz in a rod-type thulium-doped photonic crystal fiber with 80 μm core diameter. The rod is pumped with a 793 nm laser diode and produces the highest peak power at 1 kHz repetition rate with 6.5 ns pulse duration and more than 7 W average output power.

1 μJ, sub-500 fs chirped pulse amplification in a Tm-doped fiber system.

We demonstrate a Tm-doped fiber laser system producing ~300 fs pulses with 1 μJ energy, corresponding to peak powers greater than 3 MW. Pulses of 150 fs with 30 nm spectral bandwidth and 3 nJ pulse energy are generated in a Raman-soliton self-frequency shift amplifier, then stretched to ~160 ps using a chirped Bragg grating. The 60 MHz oscillator repetition rate is reduced to 100 kHz using an electro-optic modulator.

Comparison of higher-order mode suppression and Q-switched laser performance in thulium-doped large mode area and photonic crystal fibers.

We report the influence of higher order modes (HOMs) in large mode fibers operation in Q-switched oscillator configurations at ~2 μm wavelength. S(2) measurements confirm guiding of LP(11) and LP(02) fiber modes in a large mode area (LMA) step-index fiber, whereas a prototype photonic crystal fiber (PCF) provides nearly single-mode performance with a small portion of light in the LP(11) mode. The difference in HOM content leads to a significant difference in Q-switched oscillator performance.

CW-lasing and amplification in Tm(3+)-doped photonic crystal fiber rod.

We report lasing and amplification in a rod type thulium-doped photonic crystal fiber with 80 μm core diameter. The rod is pumped with a 793 nm laser diode and produces more than 20 W output power at a beam quality M(2)<1.3.

Integrated Tm:fiber MOPA with polarized output and narrow linewidth with 100 W average power.

We report on a Tm:fiber master oscillator power amplifier (MOPA) system producing 109 W CW output power, with >15 dB polarization extinction ratio, sub-nm spectral linewidth, and M2 <1.25. The system consists of polarization maintaining (PM) fiber and PM-fiber components including tapered fiber bundle pump combiners, a single-mode to large mode area mode field adapter, and a fiber-coupled isolator.

Q-switched thulium-doped photonic crystal fiber laser.

We report a novel, Tm-doped photonic crystal fiber (PCF) actively Q-switched oscillator that provides ~8.9 kW peak power with 435 µJ, 49 ns pulses at 10 kHz repetition rate at 2 μm wavelength. This fiber has a mode-field area >1000 μm2, the largest of any flexible PCF providing diffraction-limited beam quality to the best of our knowledge.

Lasing in thulium-doped polarizing photonic crystal fiber.

We describe lasing of a thulium-doped polarizing photonic crystal fiber. A 4 m long fiber with 50 μm diameter core, 250 μm diameter cladding, and d/Λ ratio of 0.18 was pumped with a 793 nm diode and produced a polarized output with a polarization extinction ratio (PER) of 15 dB and an M(2) of <1.

Spectral narrowing and stabilization of thulium fiber lasers using guided-mode resonance filters.

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.

High-power widely tunable thulium fiber lasers.

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.