Double-clad Silica Fiber Laser Research Articles

Actively mode-locked Tm(3+)-doped silica fiber laser with wavelength-tunable, high average output power.

A diode-pumped, actively mode-locked high-power thulium (Tm3+)-doped double-clad silica fiber laser is demonstrated, providing an average output power in mode-locked (continuous wave) operation of 53 W (72 W) with a slope efficiency of 34% (38%). Mode-locking in the 6th-harmonic order was obtained by an acousto-optic modulator driven at 66 MHz without dispersion compensation. The shortest measured output pulse width was 200 ps. Owing to a diffraction grating as cavity end mirror, the central wavelength could be tuned from 1.95 to 2.13 μm. The measured beam quality in mode-locked and continuous wave operation has been close to the diffraction limit.

227-W output all-fiberized Tm-doped fiber laser at 1908 nm

In this paper, we report that a diode-pumped thulium-doped double clad silica fiber laser can provide powers of up to 227 W at 1908 nm, corresponding to a slope efficiency of 54.3%, and an optical-to-optical efficiency of 51.2%. The output power, to the best of our knowledge, is the highest output at 1908 nm. The beam quality M2 factor is about 1.56. Also discussed in this paper is the dependence of the laser performance on fiber length.

2.4-W Narrow-Linewidth Q-Switched $\hbox{Tm}^{3+}$-Doped Double-Clad Fiber Laser

A narrow-linewidth 793-nm diode-pumped Tm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped double-clad silica fiber laser operated at 2 μm and actively Q-switched with an acousto-optic modulator is reported. Using a fiber Bragg grating as an output coupler, approximately 0.1-nm linewidth at 1996.8-nm pulses is derived at 80-kHz repetition rate. The maximum average output power is above 2 W for 11.6-W absorbed pump power. Less than 150-ns pulse is obtained at the repetition rate of 30 kHz. The laser is a promising seed laser for amplification in a master oscillator power amplifier system.

High-power actively mode-locked sub-nanosecond Tm^3+-doped silica fiber laser

A diode-pumped actively mode-locked Tm³⁺-doped double-clad silica fiber laser providing up to 11.8 W of average output power and pulse widths in mode-locked operation of 38 ps at a repetition rate of 37.88 MHz is reported. Pulse energies of up to 314 nJ were obtained.

High efficient Tm3+ doped double cladding silica fiber laser with an intracavity biconical taper

A high efficient LD (laser diode) pumped Tm3+ doped double clad silica fiber laser with an intravacity biconical taper was reported. A biconical taper located ∼3 cm from the output end of the fiber laser was fabricated by heating and stretching method with a length 1.5 cm and waist diameter ∼20 µm. The slope efficiency was 49.8% with respected to the launched pump power, and the maximum output power was 1.97 W. Pre and post output laser power ratio was ∼10. This fiber laser was compared with other three biconical tapered fiber lasers (the same fiber with different tapers) and a uniform geometry fiber laser. With intracavity biconical tapers, fiber lasers’ thresholds were ∼1 W higher than the fiber laser without the taper (1.97 W). The pump end’s slope efficiencies of fiber lasers with tapers were 3–5% in contrast with 37.6% of the uniform one. After tapered, the pre and post laser power ratios were much higher than the un-tapered one’s, but not changed much with the launched pump power.

A Yb^3+/Tm^3+/Ho^3+ triply-doped tellurite fibre laser

Continuous wave laser emission at 2.1 microm from a Yb(3+)/Tm(3+)/Ho(3+) triply-doped tellurite fibre laser is reported. The fibre was pumped at 1.1 microm by a Yb(3+)-doped double-clad silica fibre laser. For a 17 cm fibre length and 99%???60% reflectance cavity, the threshold was 15 mW and the slope efficiency was 25%. A maximum output of 60 mW was observed for a launched pump power of 270 mW, corresponding to 22% optical-to-optical efficiency.

High-pulse-energy, actively Q-switched Tm^3+,Ho^3+-codoped silica 2μm fiber laser

A diode-pumped Q-switched Tm(3+),Ho(3+)-codoped double-clad silica fiber laser is reported providing average powers of up to 12.3 W at 2072.7 nm and stable pulse widths of only 45 ns and repetition rates in the range 10-100 kHz. Instabilities in pulse shape occur at nonoptimum cavity alignment and were found to be linked to the mechanism responsible for self mode locking.

∼2 μm Tm3+/Yb3+-doped tellurite fibre laser

We present, for the first time, laser emission in the range 1.910–1.994 μm in Tm3+/Yb3+-doped tellurite fibre when pumped using an Yb3+-doped double-clad silica fibre laser operating at 1.088 μm. With this pump scheme there was strong pump excited state absorption (ESA) which caused upconversion emission at 800 nm and 480 nm due to the Tm3+: 3H4 → 3H6 and Tm3+: 1G4 → 3H6 transitions, respectively. This strong ESA limited the maximum slope efficiency to 10% with respect to absorbed pump power, and the maximum output power to 67 mW. This is however the highest output power which has been achieved in a tellurite fibre laser so far. The lowest observed threshold was 114 mW for a 22 cm long fibre and a 90% reflective output coupler. Further power scaling was limited due to thermal damage at the pump end of the fibre. The optimum fibre length for this arrangement was around 16 cm but lasing was achieved in lengths ranging from <9 to 30 cm. Tellurite glass offers significant advantages over silicate and fluoride glasses which make it a very promising material for compact, medium power, near and mid-IR fibre lasers for range-finding, medical and atmospheric monitoring and sensing applications.

High-pulse-energy actively Q-switched Tm^3+-doped silica 2 μm fiber laser pumped at 792 nm

A diode-pumped Q-switched Tm(3+)-doped double-clad silica fiber laser is reported providing average powers of up to 30 W at pulse widths of only 41 ns and repetition rates in the range of 10-125 kHz. Up to 270 microJ pulse energy was produced. Amplified spontaneous emission (ASE) buildup limits the maximum peak power, and the pump power and average output power at the point of ASE induced clamping were found to depend linearly on the repetition rate.

Diode-cladding-pumped singly Ho3+-doped silica fibre laser

An unsaturated continuous-wave output power of 109 mW was produced from a diode-pumped Ho3+-doped double-clad silica fibre laser that did not require the use of a sensitiser. The laser operated with a slope efficiency of 7% and an emission wavelength of 2.14 µm. Energy transfer upconversion may have adversely affected the performance of the laser.

Output dynamics and stabilisation of a multi-mode double-clad Yb-doped silica fibre laser

The intensity dynamics of the double-clad Yb fibre laser have been characterised. Stabilisation of the fibre laser intensity by using uniform bi-directional pumping is demonstrated. For the single-end-pumped Yb fibre laser, the output becomes more stable for the shorter fibre length due to the higher threshold of stimulated Brillouin scattering, SBS, and Kerr effects and the reduction of saturated absorber effects caused by any unpumped fibre section. By additional pumping in a double-end-pumped configuration, the output power can be scaled higher before detecting high intensity pulses initiated by SBS in the Yb fibre laser due to the reduction of saturable absorption effect. It is confirmed that uniform pumping enhances the stability of the laser output.

Gain-switched Tm3+-doped double-clad silica fiber laser

A gain-switched Tm-doped double-clad silica fiber laser operating at a wavelength of approximately 2microm with moderate output energy of 14.7mJ per pulse and a slope efficiency of 39.5% (with respect to launched pump energy) is realized pumped at 1.064microm from a Nd:YAG laser. The gain-switched fiber laser pulses are built up by a series of relaxation spikes, and every spike pulse duration is nearly 1micros. The output wavelength becomes longer, and the slope efficiency increases with the increase in fiber length.

High-power diode-cladding-pumped Tm 3+ , Ho 3+ -doped silica fibre laser

The fundamental characteristics of a continuous-wave high-power diode-pumped Tm3+, Ho3+-doped double-clad silica fibre laser are presented. A maximum output power of 5.2 W was measured and was generated at a slope efficiency of 42 (44)% with respect to the launched (absorbed) pump power. At the optimum length of 7 m (αeffL=2.9, where αeff is the effective absorption coefficient of the fibre and L is the fibre length), the fibre laser output was measured to have a centre wavelength of 2105 nm and a line width of ∼20 nm. The centre wavelength of the emission was tunable over a 32-nm extent when 0.68<αeffL<3.28 or for a 6.2-m change in L.

Efficient high power operation of a Nd:YAG-pumped Yb:Er-doped silica fibre laser

Approximately 1.4 W of cw output is generated when a Yb:Er-co-doped double-clad silica fibre laser is pumped with the 1.064-μm output from a high power Nd:YAG laser. A maximum slope efficiency of 19% with respect to the launched pump power is produced from the fibre laser. The fibre laser-operating wavelength extends between 1.56 μm and 1.57 μm when the length of fibre was increased from 1.8 m to 7 m. Self-sustained relaxation oscillations are consistently observed in the output from the fibre laser for all fibre configurations investigated. Preliminary experiments relating to the use of the Yb:Er-co-doped fibre laser as a pump source for Tm:Ho-co-doped silica fibre lasers are also presented.