Nicolaie Pavel
University of Hamburg
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Publication
Featured researches published by Nicolaie Pavel.
Applied Physics Letters | 2003
Yoichi Sato; Takunori Taira; Nicolaie Pavel; Voicu Lupei
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.
Optics Express | 2011
Nicolaie Pavel; Masaki Tsunekane; Takunori Taira
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.
Applied Physics Letters | 2001
Voicu Lupei; A. Lupei; Nicolaie Pavel; Takunori Taira; Ichiro Shoji; A. Ikesue
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.
Applied Physics Letters | 2003
M. Iwai; T. Yoshino; S. Yamaguchi; M. Imaeda; Nicolaie Pavel; Ichiro Shoji; Takunori Taira
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.
Japanese Journal of Applied Physics | 2001
Nicolaie Pavel; Jiro Saikawa; Sunao Kurimura; Takunori Taira
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.
Applied Physics Letters | 2002
Voicu Lupei; Nicolaie Pavel; Takunori Taira
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.
Applied Physics Letters | 2002
Voicu Lupei; Nicolaie Pavel; Takunori Taira
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.
Optics Express | 2006
André Richter; Nicolaie Pavel; E. Heumann; Günter Huber; Daniela Parisi; A. Toncelli; M. Tonelli; Andreas Diening; Wolf Seelert
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.
Optics Express | 2005
Nicolaie Pavel; Voicu Lupei; Takunori Taira
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.
Optics Communications | 2002
Voicu Lupei; Nicolaie Pavel; Takunori Taira
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.