Diode-pumped cw and Q-switched Nd:GdVO4 laser operating at 1.34 μm

A diode-pumped 1.34 m Nd:GdVO₄ laser operating in cw and active Q-switching modes has been demonstrated. 4.15 W of cw output power was obtained at the highest attainable pump power of 12.3 W, resulting in an optical conversion efficiency of 33.7%, the slope efficiency was determined to be 37.6%. In Q-switching operation, a maximum average output power of 2.7 W was generated at pulse repetition frequency (PRF) of 50 kHz, with an optical conversion efficiency of 22% and a slope efficiency of 29.2%. The laser pulses with shortest duration, highest energy and peak power were achieved at PRF of 10 kHz, the parameters being 15 ns, 160 J, and 10.7 kW, respectively. By intracavity frequency-doubling with a type II phased-matched KTP crystal, 0.62 W average power at 0.67 m was produced at a PRF of 15 kHz, the resulting pulse energy, peak power, and pulse width being 41.3 J, 2.2 kW, and 19 ns, respectively. A group of analytical formulae, based on rate equations, are presented to evaluate the operational parameters of an actively Q-switched laser. Calculated results were found to be in close consistency with the experimental data.     

A 13.3-W laser-diode-array end-pumped Nd:GdVO4 continuous-wave laser at 1.34 μm

We report a high-power laser-diode-array end-pumped 0.3 at.% Nd:GdVO₄ continuous-wave laser operating at 1.34 m. The maximum output power of 13.3 W was obtained at the incident pump power of 49.2 W, giving the corresponding optical conversion efficiency of 27% and the average slope efficiency of 28.5%. The thermal focal length of the Nd:GdVO₄ crystal under the pump power from 15.3 to 50 W was measured experimentally. PACS 42.55.Xi; 42.70.Hj     

Efficient Ho : YAG laser pumped by a cladding-pumped tunable Tm : silica-fibre laser

Highly efficient room-temperature operation of a Ho:YAG laser end pumped by a cladding-pumped tunable Tm-doped silica-fibre laser operating at 1905 nm is reported. Using a simple two-mirror resonator configuration, we obtained 6.4 W of unpolarized output at 2097 nm in a diffraction-limited TEM₀₀ beam (with M²1.1) for 9.6 W of incident pump power, corresponding to a slope efficiency with respect to incident pump power of 80% and an optical-to-optical efficiency of 67%. Using a folded-resonator configuration incorporating a Brewster-angled glass plate, we obtained 5.8 W of linearly polarized TEM₀₀ output, corresponding to an optical-to-optical efficiency of 60%. Due to low quantum defect heating, the depolarization loss due to thermally induced birefringence in the Ho:YAG crystal was <0.14% at the maximum available pump power, indicating that there is scope for further power scaling. PACS 42.55.-f; 42.55.Xi; 42.55.Wd; 42.60.Pk     

High-efficiency continuous-wave diode-pumped Tm:Ho:LuAG laser at 2.1 μm

Continuous Wave (CW) laser action has been observed from a Ho:Tm:LuAG rod at 2.1 m pumped by a diode laser at 785 nm in the temperature range of 77–200 K. The maximum power observed was 1.38 W at an incident power of 4 W at a crystal temperature of 77 K. The optical-to-optical conversion efficiency was observed to be 35.6% at a threshold power of 0.2 W with a 95% output coupling mirror.     

Comparison of Yb-doped fiber laser with one-end and double-end pumping configuration

A high-power Ytterbium-doped fiber laser (YDFL) with homemade double clad fiber (DCF) is introduced in this paper. The output power characteristics of a linear cavity fiber laser have been studied theoretically by solving the rate equations and experimentally tested with single- and double-end-pumping configurations. When both ends of the fiber are pumped by two high-power laser diodes with a launched power of 300 W each, a maximum CW output of 444 W is obtained with a slope efficiency of 75%.     

High power single-longitudinal-mode operation in a twisted-mode-cavity laser with a c-cut Nd:GdVO4 crystal

A twisted-mode-cavity laser was established by using a piece of c-cut Nd:GdVO₄ crystal as the lasers active material. Output spectra were scanned by a scanning Fabry–Perot interferometer, which demonstrated that the single-longitudinal-mode laser operation was realized in the twisted-mode-cavity laser configuration. A maximum single-longitudinal-mode laser output power of 2.1 W was obtained when the pump power was 11.5 W. The pump slope efficiency was about 20.0%. A passively Q-switched single-longitudinal-mode laser was also achieved in a twisted-mode cavity by inserting a piece of Cr⁴⁺:YAG as an intracavity saturable absorber. The Q-switched single-longitudinal-mode laser pulse duration was measured to be 100 ns and the single-pulse energy was about 40.0 J.     

High average power Q-switched green beam generation by intracavity frequency doubling of diode-side-pumped Nd:YAG/HGTR-KTP laser

To obtain high power and high beam quality second harmonic generation, a Q-switched system has been demonstrated by intracavity frequency doubling of two diode-side-pumped Nd:YAG modules with double AO-modulators in an astigmatism compensated cavity geometry. A maximum average frequency doubled power of 185 W is obtained when the pumping power is 600 W for each module. The corresponding optical-to-optical conversion efficiency is 15.4% and the pulse width is 180 ns at a repetition rate of 10 kHz. An instability of 2.5% was measured over a period of 2 h and the beam quality factors were measured to be , the maximum output power.     

Edge-pumped, folded zig-zag Nd:YAG slab laser

 We report the design and performance of conduction-cooled, edge-pumped, folded zig-zag continuous wave Nd:YAG slab laser. The Nd:YAG slab is pumped with waveguide coupled laser diode bars. The coupling efficiency of waveguide to laser diode radiation is 97%. In a folded zig-zag resonator, a maximum output power of 37 W in multimode operation is achieved for an incident pump power of nearly 180 W on the Nd:YAG slab. This corresponds to an optical-to-optical conversion efficiency of 20% and slope efficiency of 32%. We obtained more than 10 W of output power with the beam quality factors in the width dimension and in the thickness dimension equal to 8.     

Efficient blue laser generation at 473 nm by a BIBO crystal

It is reported that efficient blue laser generation at 473 nm in a BIBO crystal at type-I phase matching direction of (θ,)=(18.3°,90°) performed with a diode-pumped Nd:YAG laser. With incident pump power of 1.6 W, output power of 183 mW at 473 nm has been obtained using a 5.0 mm-long BIBO crystal. The optical conversion efficiency was up to 11.4%. It was found that the intracavity frequency doubling efficiency is about 50% greater than that obtained with a 10 mm-long type-I phase-matching LBO crystal.     

High-power continuous-wave operation of a diode-pumped laser at

The continuous-wave laser properties of an efficient diode-pumped Nd:GdVO₄ crystal operating at formed with a simple plane-concave cavity have been studied. With the incident pump power of 21 W, an output power of 6.9 W was obtained, giving an optical conversion efficiency of 32.8% and a slope efficiency of 35.3%. The laser characterization of two different Nd³⁺-doped concentration of Nd:GdVO₄ crystals were studied.     

A high-average-power diode-pumped Nd:YVO4 regenerative laser amplifier for picosecond-pulses

A 5.3 W average output power at a pulse repetition-rate of 40 kHz was achieved with a diode-end-pumped Nd:YVO₄ regenerative amplifier. In a continuous-wave operation an optical efficiency of 43% was reached. The output pulse duration is 19 ps, if seeded by a 7-ps-oscillator. A maximum pulse repetition-rate of 80 kHz and a maximum pulse energy of 350 J were generated by the entire laser system. PACS 42.65.Re; 42.79.Kr; 42.79.Hp     

Performance studies of diode-side-pumped CW Nd:YAG laser in copper coated optical pump cavity

This paper reports the performance studies of Nd:YAG rods with different diameters and doping concentration in the CW diode-side-pumped geometry. We have used p-polarized diodes to pump the active medium and we studied the performance of different rods in terms of thermal lensing, its fluorescence profile, power output, and M² factor of the laser beam. We achieved a maximum of 378 W of output power for an input pump power of 757 W, which corresponds to optical conversion efficiency close to 50%. The slope efficiency of the system was 56.4%. These efficiencies are the highest reported to the best of our knowledge and we achieved with Nd:YAG rod at 1.1-at% doping.     

Phase conjugation in an optical fibre

We report experimental studies of phase conjugation by stimulated Mandelstam Brillouin scattering in multimode fibres. A dramatic decrease in the threshold power as compared to that (10⁴ to 10⁵ W) typically observed in conventional media was achieved. A ruby pulsed pump with 500-ns pulses was used. For the 7-m-long fibre, the threshold power was 50 W, the degree of phase conjugation was almost one, the pump-to-Stokes conversion efficiency was about 80%. For the 130-m-long fibre, the threshold power decreased to 10 W and the pump-to-Stokes conversion efficiency reached 100%. Polarization scrambling was observed in the 130-m-long fibre, but the Stokes wave with polarization coinciding with that of the pump wave was a phase-conjugate replica of the pump, as before.     

High-power diode-cladding-pumped Tm<Superscript>3+</Superscript>, Ho<Superscript>3+</Superscript>-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 (_effL=2.9, where _eff 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<_effL<3.28 or for a 6.2-m change in L. PACS 42.55.Wd; 42.55.Xi; 42.60.Lh; 42.60.Pk     

Erratum: ‘A copper HyBrlD laser of 120W average output power and 2.2% efficiency’

Erratum: A copper HyBrlD laser of 120W average output power and 2.2% efficiency     

A new design for rf-excited CO2 lasers

In this paper a new four-pole electrode design for radiofrequency excited CO₂ lasers is described. Here, the two functions of the discharge tube, rf-excitation and dischare cooling can be optimized separataly. With a symmetric rf excitation technique electromagnstic interference is also minimized. A prototype laser with 50 cm cavity length produced about 2.5 W laser output power at 5% efficiency.     

Diode-pumped quasi-three-level Nd:CLNGG laser at 928 nm

We describe the output performances of the 928 nm ⁴ F _3/2 → ⁴ I _9/2 transition in Nd:CLNGG under diode-laser pumping. An end-pumped Nd:CLNGG crystal yielded 1.3 W of continuous-wave output power for 17.8 W of absorbed pump power. The slope efficiency with respect to the absorbed pump power was 11.2%. Furthermore, with 17.8 W of diode pump power and the frequency-doubling crystal LiB₃O₅ (LBO), a maximum output power of 260 mW in the blue spectral range at 464 nm has been achieved. The blue output power stability over 4 h is better than 3.2%.     

Q-switched Yb 3+ :YVO 4 laser with Raman self-conversion

We report the efficient continuous-wave (CW) and Q-switched laser operation of a diode-pumped Yb:YVO₄ laser. A CW output power of 1 W with a slope efficiency of 59% with respect to absorbed pump power was demonstrated. Passively Q-switched with a Cr⁴⁺:YAG saturable absorber, a Yb:YVO₄ laser with Raman conversion was demonstrated. Q-switched 18.7- J pulses with a pulse duration of 17 ns and a peak power up to 1 kW were obtained at 1018-nm fundamental wavelength and 3.6- J pulses with a pulse duration of 6 ns and a peak power of about 0.6 kW were obtained at 1119.5-nm first-Stokes wavelength.This revised version was published online in March 2005. In the previous version, the published online date was missing     

Compact efficient self-frequency Raman conversion in diode-pumped passively Q-switched Nd:GdVO<Subscript>4</Subscript> laser

I report the first demonstration of the generation of efficient sub-nanosecond self-stimulated Raman pulses by a diode-pumped passively Q-switched Nd:GdVO₄/Cr⁴⁺:YAG laser. The conversion efficiency for the average power is 7% from pump diode input to self-Raman output and the slope efficiency is up to 14%. At an incident pump power of 2.0 W, the pulse duration, pulse energy, and peak power for the Stokes wavelength of 1175.6 nm were found to be 750 ps, 6.3 J, and 8.4 kW, respectively, with a pulse-repetition rate of 22 kHz. PACS 42.55.Ye; 42.55.Xi; 42.60.Gd