Nicolaie Pavel

Laser operation with near quantum-defect slope efficiency in Nd:YVO4 under direct pumping into the emitting level

One-micron continuous-wave (cw) laser emission with 0.80 slope efficiency (0.79 optical-to-optical efficiency) under Ti: sapphire and 0.75 slope efficiency relative to absorbed power under diode-laser pumping at 880 nm into the emitting level is demonstrated in a 1-mm-thick, 1.0-at. % Nd:YVO4 crystal. These values are superior to those obtained with 809-nm pumping into the level 4F5/2, and can be explained consistently by the effect of the quantum defect between the pump and laser radiation, the superposition of pump and laser mode volumes, the pump-level efficiency and the residual optical losses. In the analysis of the 809-nm pumping data a pump-level efficiency equal to the unity was employed, as determined with a method based on the pump-saturation effects on absorption.

Composite, all-ceramics, high-peak power Nd:YAG/Cr 4+ :YAG monolithic micro-laser with multiple-beam output for engine ignition

A passively Q-switched Nd:YAG/Cr(4+):YAG micro-laser with three-beam output was realized. A single active laser source made of a composite, all-ceramics Nd:YAG/Cr(4+):YAG monolithic cavity was pumped by three independent lines. At 5 Hz repetition rate, each line delivered laser pulses with ~2.4 mJ energy and 2.8-MW peak power. The M(2) factor of a laser beam was 3.7, and stable air breakdowns were realized. The increase of pump repetition rate up to 100 Hz improved the laser pulse energy by 6% and required ~6% increase of the pump pulse energy. Pulse timing of the laser-array beams can by adjusted by less than 5% tuning of an individual line pump energy, and therefore simultaneous multi-point ignition is possible. This kind of laser can be used for multi-point ignition of an automobile engine.

Laser emission under resonant pump in the emitting level of concentrated Nd:YAG ceramics

The possibility of using the thermally activated optical absorption bands for a resonant pump in the emitting level of highly doped Nd laser materials is discussed. This potential is demonstrated by the continuous wave 1064 nm laser emission under 885 nm pump in concentrated (up to 6.8 at. %) Nd:YAG ceramics.

High-power blue generation from a periodically poled MgO :LiNbO3 ridge-type waveguide by frequency doubling of a diode end-pumped Nd :Y3Al5O12 laser

Continuous-wave power of 189 mW at 473 nm with 49% conversion efficiency is generated from a 8.5 mm long uncoated periodically polled MgO:LiNbO3 ridge-type waveguide by frequency doubling of a diode end-pumped Nd:Y3Al5O12 laser at room temperature; the corresponding internal blue power and conversion efficiency were 222 mW and 58%, respectively. The highest conversion efficiency of 63% (74% with respect to the blue internal power) was obtained from a 12 mm long waveguide with 99 mW blue output power. Saturation of output blue power was observed for coupled fundamental power into the waveguides in excess of 200 mW.

High Average Power Diode End-Pumped Composite Nd:YAG Laser Passively Q-switched by Cr4+:YAG Saturable Absorber

We report a diode end-pumped composite Nd:YAG laser, passively Q-switched by a Cr4+:YAG crystal as saturable absorber. The maximum peak power exceeded 16 kW for an average power of 2.6 W, laser pulses of 16.8-ns duration and 272-µJ energy. The maximum average power was 4.2 W with the laser operating at 24.0 kHz repetition frequency and 47.8-ns pulses duration (3.7 kW peak power) at a beam quality of M2=1.34. A rate-equation model that considers both the active medium and the saturable absorber dynamics was developed. A good agreement between the experiments and modeling resulted.

Highly efficient continuous-wave 946-nm Nd:YAG laser emission under direct 885-nm pumping

The 885-nm Ti:Sapphire pumping into the emitting level 4F3/2 of Nd:YAG produces a highly efficient (0.68 slope efficiency in absorbed power) 946-nm laser emission; a strong reduction of heat generation could be also obtained.

1064 nm laser emission of highly doped Nd: Yttrium aluminum garnet under 885 nm diode laser pumping

Highly efficient 1064 nm continuous-wave laser emission under 885 nm diode pumping in concentrated Nd: Yttrium aluminum garnet (YAG) crystals (up to 3.5 at. % Nd) and ceramics (up to 3.8 at. % Nd) is reported. A highly doped (2.4 at. %) Nd:YAG laser, passively Q switched by a Cr4+:YAG saturable absorber, is demonstrated.

Continuous-wave ultraviolet generation at 320 nm by intracavity frequency doubling of red-emitting Praseodymium lasers

We describe a new approach for the generation of coherent ultraviolet radiation. Continuous-wave ultraviolet light at 320 nm has been obtained by intracavity frequency doubling of red-emitting Praseodymium lasers. Lasing at the 640-nm fundamental wavelength in Pr:LiYF(4) and Pr:BaY(2)F(8) was realized by employing an optically pumped semiconductor laser at 480 nm as pump source.Using LiB(3)O(5) as nonlinear medium, ~19 mW of ultraviolet radiation with ~9% optical efficiency with respect to absorbed power was reached for both laser crystals; the visible-to-ultraviolet conversion efficiency was 26% and 35% for Pr:LiYF(4) and Pr:BaY(2)F(8), respectively.

1.34-μm efficient laser emission in highly-doped Nd:YAG under 885-nm diode pumping

We report on 1.34-mum laser emission in Nd:YAG under diode pumping at 885 nm, directly into the 4F3/2 emitting level. 3.8 W of output power with 0.26 overall optical-to-optical efficiency was recorded from a 2.5- at.% Nd:YAG single-crystal. Comparative results obtained by classical pumping at 809 nm, in the highly absorbing 4F5/2 level, are presented, showing the advantage of the direct pumping. The influence of lasing wavelength and Nd concentration on the thermal effects induced by optical pumping into the active component is discussed.

Highly efficient laser emission in concentrated Nd:YVO4 components under direct pumping into the emitting level

Abstract Reduction of the quantum defect in four-level lasers by pumping directly into the emitting level can improve laser emission parameters and diminish heat generation. Using concentrated components can compensate reduced absorption in the emitting level of Nd laser materials. These benefits are demonstrated by stable and highly efficient 1064 nm continuous-wave laser emission of Nd:YVO 4 components of 1, 2 and 3 at.% Nd under end-pumping into 4 F 3/2 at 878.6 nm with a Ti:sapphire laser.