Efficient Cw Operation Research Articles

Alexandrite: an attractive thin-disk laser material alternative to Yb:YAG?

Yb:YAG thin-disk (TD) technology has enabled construction of laser/amplifier systems with unprecedented average/peak power levels, and has become the workhorse of many scientific investigations. On the other hand, for some applications, the narrow emission bandwidth of Yb:YAG limits its potential, and the search for alternative broadband TD gain media with suitable thermo-optomechanical parameters is ongoing. The alexandrite gain medium has a broad emission spectrum centered around 750 nm, possesses thermomechanical strength that even outperforms Yb:YAG, and has unique spectroscopic properties enabling efficient laser operation even at elevated temperatures. In this work, we have numerically investigated the power scaling potential of continuous-wave (cw) alexandrite lasers in TD geometry for the first time. Using a detailed laser model, we have compared the potential cw laser performance of Yb:YAG, Ti:Sapphire, Cr:LiSAF, Cr:LiCAF, and alexandrite thin-disk lasers under similar conditions and show that among the investigated transition metal-doped gain media, alexandrite is the best alternative to Yb:YAG in power scaling studies at room temperature. Our analysis further demonstrates that potentially Ti:Sapphire is also a good alternative TD material, but only at cryogenic temperatures. However, in comparison with Yb:YAG, the achievable laser gain is relatively low for both alexandrite and Ti:Sapphire, which then requires usage of low-loss cavities with small output coupling for efficient cw operation.

Highly efficient CW operation of a diode pumped Nd:Y2O3 ceramic laser

High efficiency continuous-wave laser operation of an in-house made Nd:Y2O3 ceramic was demonstrated. The Nd:Y2O3 laser ceramic was fabricated by vacuum sintering plus the hot isostatic pressing process, whose in-line transmittance reaches 81.6% at the wavelength of 1000 nm. The 1.08 and 1.36 µm CW laser oscillation of an uncoated ceramic sample was experimentally investigated. Both achieved the highest slope efficiency and output power so far reported for the Nd:Y2O3 ceramic lasers. For the operation of 4F3/2-4I11/2 transitions, simultaneous oscillations at 1074.6 nm and 1078.8 nm were observed. At an absorbed pump power of 7.0 W, a maximum output power of 3.01 W was obtained with a slope efficiency of 49.6%. For the laser operation of 4F3/2-4I13/2 transitions, a 1.68 W single wavelength at 1357.7 nm with the slope efficiency of 29.3% was achieved at the absorbed pump power of 6.7 W.

Highly efficient 10 cm long fiber laser.

We investigate an innovative multipass-pumping technique in a short photonic crystal fiber laser. The technique is based on simple optical elements and shows, in a power oscillator configuration, highly efficient CW and Q-switched operation of an extremely short fiber laser. We report significantly higher absorption of the pump light, compared to a single-pass configuration, which results in an impressive fourfold increase in slope efficiency, up to 60%. Moreover, we show pulse energy of 1.22mJ and pulse duration shorter than 12ns, corresponding to a peak power of more than 100kW.

Highly efficient continuous-wave Nd:YAG ceramic lasers at 946 nm

Highly efficient CW operation of diode-end-pumped Nd:YAG ceramic lasers at 946 nm is experimentally demonstrated. When a 5 mm long in-house fabricated Nd:YAG ceramic was used as the gain medium, a maximum output power of 10.5 W was obtained under an incident pump power of 35 W, corresponding to an optical conversion efficiency of 30%, while, when a 3 mm long ceramic sample was used, a maximum output power of 8.7 W was generated with a slope efficiency of 65% with respect to the absorbed pump power. Both the optical conversion efficiency and slope efficiency are the highest results reported so far for the diode-pumped 946 nm lasers.

80-fs Nd:silicate glass laser pumped by a single-mode 200-mW diode

A Nd(3+)-doped Schott LG680 silicate glass laser was pumped with a single-mode 200-mW diode. Efficient cw operation was demonstrated with 37.5 mW output power and 36% slope efficiency. Passive mode-locking with a semiconductor saturable absorber mirror yielded 80-fs pulses with a two-prism setup. Alternatively, pulses of approximately 200-fs, tunable over the range 1058-1076 nm, were obtained with either slit-tuning or a single-prism dispersive resonator. Output powers from 6 to 14 mW have been measured.

Low-threshold femtosecond Nd:glass laser

Using a 150-mW single-transverse-mode laser diode at 802 nm for pumping an Nd:phosphate laser, we achieved efficient cw operation (40% slope efficiency) with pump threshold as low as 12 mW at optimum coupling, and a maximum output power of 53 mW. Under passive mode-locking operation, we obtained nearly Fourier-limited 270-fs pulses in a prismless dispersion-compensated cavity and 173-fs pulses with a single-prism setup. This compact laser is especially interesting for applications requiring low power levels, such as seeding amplifiers and for biodiagnostics.

Efficient cw operation of diode-pumped Nd:YLF lasers at 1312.0 and 1322.6 nm for a silver atom optical clock

We describe the efficient cw operation of two Nd:YLF lasers at 1312.0 and 1322.6 nm for the development of a silver atom optical clock. For a simple linear cavity laser configuration investigated at these wavelengths, we have obtained an output power of 3.6 W at 1312.0 nm for 13.8 W of absorbed pump power ( λ=806 nm) and 4.8 W output at 1322.6 nm with 16.3 W pump. At 1312.0 nm, using a twisted-mode cavity, a single-frequency output power of 750 mW has been obtained. Single-frequency operation (450 mW) at 1322.6 nm was achieved using an intra-cavity solid etalon.

Efficient high power operation of erbium 3 µmfibre laser diode-pumped at 975 nm

Efficient CW operation of a 2.71 um Er,Pr:ZBLAN double-clad fibre laser pumped with a single diode laser operating at a wavelength of 975 nm is described. A maximum output power of 0.5 W and a slope efficiency of 25% (with respect to the launched pump power) were obtained. Threshold pump powers of < 200 mW launched were measured and consistent relaxation oscillations in the output from the fibre laser indicate the presence of a saturable absorption mechanism.

Efficient high power operation of a Tm-doped silica fiber laser pumped at 1.319 μm

Efficient cw and Q-switched operation of a Tm-doped silica fiber laser, pumped with the 1.319-μm output from a Nd:YAG laser, is described. An unsaturated continuous wave maximum output power of 310 mW and a slope efficiency of 23% was obtained for a near optimised cavity. A relatively low measured absorption cross section in conjunction with excited state absorption (ESA) of the pump light results in a minimum threshold pump power of 0.9 W. Q-switching by use of a mechanical chopper resulted in 16 W/280 ns pulses at a repetition rate of 20 kHz.

High-power diode-bar-pumped intracavity-frequency-doubled Nd:YLF ring laser

We report efficient cw operation of an intracavity-frequency-doubled Nd:YLF ring laser end-pumped by two beam-shaped 20 W diode bars. A single-frequency polarised output of 6.2 W at 526.5 nm (8.3 W generated in the doubling crystal) was obtained in a TEM 00 mode ( M 2<1.2).

High-power diode-bar end-pumped Nd:YLF laser at 1053??µm

We describe efficient cw operation of a Nd:YLF laser end pumped by two beam-shaped 20-W diode bars on the 1.053-microm transition. Fundamental transverse-mode operation with output power of 11.1 W for ~29.5 W of incident pump power was demonstrated. In Q-switched operation 8.4 W of average power at a pulse repetition frequency of 40 kHz and ~2.6-mJ pulse energy at a pulse repetition frequency of 1 kHz were achieved.

Efficient Nd:YAG laser end pumped by a 20-W diode-laser bar

We describe efficient cw operation of a Nd:YAG laser longitudinally pumped by a 20-W cw diode-laser bar by use of a novel pump reshaping and focusing scheme. Fundamental-transverse-mode operation at 1.064 microm with output powers of 6 W (unpolarized) and 5.3 W (linearly polarized) for 14.4 W of incident pump power have been demonstrated.

High-efficiency CW operation of 890 nm pumped holmium fluoride fibre laser

Highly efficient CW operation has been observed from the holmium transition centred at 2.024 μm in a Tm:Ho co-doped single-mode fluoride fibre laser. When pumping holmium directly at 890 nm a minimum threshold of 8.2 mW launched pump power was observed for oscillation at 2.076 μm. A maximum slope efficiency of 30% was achieved for operation at 2.054 μm, which corresponds to a photon conversion efficiency of 69%

Efficient resonantly pumped 28-μm Er^3+:GSGG laser

Efficient cw operation of the Er(3+):GSGG (4)I(11/2)?(4)I(13/2) laser transition at 2.8 microm is demonstrated at room temperature. The (4)I(11/2) upper laser state is directly pumped at 0.97 microm. The slope efficiency for the 2.8-microm laser is 36%, indicating a greater than unity quantum efficiency. This excess efficiency results from the recycling of population through upconversion out of the lower laser state.

Nd:MgO:LiNbO/sub 3/ channel waveguide laser devices

A report is presented on the fabrication and efficient CW operation at 1.085 mu m of Nd:MgO:LiNbO/sub 3/ proton-exchanged channel waveguide lasers and amplifiers optically pumped at 0.814 mu m. Thresholds as low as 1.5 mW and slope efficiencies up to 34% were achieved in monolithic miniature laser devices. Up to 14 mW of output power could be achieved without observation of photorefractive damage. Diode laser pumping was also demonstrated. For the amplifier a small-signal gain of 7.5 dB was achieved for 22 mW of coupled pump power. Experimental results were analyzed with the use of a mode overlap formalism and a value of 0.93 was found for the pump quantum efficiency. Absorption spectra, fluorescence spectra, and lifetime measurements are also reported for the bulk and waveguide material.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Efficient CW operation of a 2.9 μm Ho 3+ -doped fluorozirconate fibre laser pumped at 640 nm

CW laser operation of a H03+-doped ZBLAN multimode fibre, emitting within the range 2.83–2.95 μm, was achieved by optical pumping at 640 nm, as a result of excited state absorption of the pump. Thresholds were approximately 65 mW absorbed power for a 90% output coupler and approximately 290 mW with reflection of the fibre end only. Slope efficiencies and maximum output powers were 2.9% and 12.6 mW, and 4.4% and 10.2 mW, respectively.

Efficient Nd:MgO:LiNbO 3 waveguide laser

Efficient CW operation of a single mode Nd:MgO:LiNbO/sub 3/ channel waveguide laser is reported. The absorbed pump power at threshold is 2.7 mW and the slope efficiency is 34%. With the available pump power the laser could emit up to 14 mW CW without exhibiting any photorefractive damage. >

Vertical-cavity surface-emitting InGaAs/GaAs lasers with planar lateral definition

A planarity preserving method for the definition of vertical-cavity surface-emitting lasers (VC-SEL) is described. A strained-layer InGaAs quantum well VC-SEL structure was grown and lasers were laterally defined using a tailored deep proton implantation process. In these lasers we obtained low threshold current densities of 1000 A/cm2 and efficient cw operation. This method facilitates large-scale integration of VC-SEL devices.

Exalite 392E: a new laser dye for efficient cw operation between 373 and 408 nm

Exalite 392E is found to offer significant improvements in the preparation of dye solutions for efficient ultraviolet dye lasers./AIP/.

Efficient CW operation of a diode-pumped YAlG:Nd laser

Efficient CW operation of a diode-pumped YAlG:Nd laser