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1
Content available remote Optimization of energetic parameters of passively Q-switched lasers.
100%
Żendzian W.
Optica Applicata
|
2000
|
tom Vol. 30, nr 2-3
383-399
EN
The paper presents optimization of energy and peak power of the pulse of laser with a slow passive Q-switch. The excited states absorption (ESA) in absorber is included in an optimization process. Using the laser model described it is possible to determine optimal values of unsaturated absorber transmission and reflectivity of the output mirror as a function of the normalized initial gain coefficient z and parameter alpha, characterizing the ratio of the absorption cross-section of nonlinear absorber to the emission cross-section of the laser medium. To optimize the passively Q-switched laser the charts and simple analytical formulas, presented in the paper, can be applied. As an example, optimization of energy and peak power of the pulse of Nd:YAG laser, with Cr/sup 4+/:YAG crystal as passive Q-switch, pumped by 100 W matrix of laser diodes is presented. It has been shown that for laser energy optimization, ESA slightly changes the value of optimal unsaturated absorber transmission and optimal reflectivity of the output mirror of the laser.
2
Content available remote Optymalizacja charakterystyk energetycznych lasera z pasywnym modulatorem dobroci rezonatora
100%
Żendzian W.
Biuletyn Wojskowej Akademii Technicznej
|
2000
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tom Vol. 49, nr 2
5-26
PL
W artykule przedstawiono proces optymalizacji prowadzący do uzyskania maksymalnej energii oraz mocy szczytowej impulsu lasera z wolnym pasywnym Q-modulatorem uwzględniający absorpcję ze stanów wzbudzonych (ESA). Przedstawiony model lasera pozwala wyznaczyć optymalne wartości transmisji początkowej nieliniowego absorbera i współczynnika odbicia zwierciadła wyjściowego w funkcji unormowanego początkowego współczynnika wzmocnienia z i parametru alfa charakteryzującego głównie stosunek absorpcyjnego przekroju czynnego nieliniowego absorbera do emisyjnego przekroju czynnego ośrodka laserowego.
EN
It is presented the optimization process for obtaining the maximal energy and peak power of the laser pulse with the free passive modulator-Q with taking into account the absorption excited states (ESA). The presented laser model enables determination the optimal initial transmission of nonlinear absorber and reflection coefficient of output reflector as a function of initial normalized amplification coefficient z and the parameter alfa wich mainly characterizes the ratio of absorption cross section of the laser medium. The analytical relations are also presented which enable to determine the laser pulse parameters: duration, energy and peak power. As an example it is presented the optimization of the Nd:YAG laser energy and power with passive modulator-Q from Cr(4+):YAG crystal pumped by matrix 100 W laser diodes. The ESA was found to exert a minimal impact on the initial optimal transmission of nonlinear absorber and on the optimal reflection coefficient of the output laser mirror and on its energetic optimization.
3
Content available remote Q-switched mode locking in diode pumped lasers
51%
Jabczyński J. K. , Żendzian W. , Kwiatkowski J.
Opto-Electronics Review
|
2005
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tom Vol. 13, No. 4
317-323
EN
The Q-switched mode locking (QML) regime provides the generation of relatively high peak power picosecond pulses train with energies of a few µJ each in a simple resonator. The critical review of QML methods and results including our investigations is given in the first part of presentation. The application of several types of saturable crystalline absorbers (Cr⁴⁺:YAG, V³⁺:YAG, LiF, GaAs) leads to chaotic, partial QML effect, with less than 100% modulation depth in principle. The fully modulated efficient QML laser was demonstrated in the next part. The acousto-optic cell playing a double role of Q-switch and mode locker was located near a flat output coupler. The two folding mirrors were mounted on the translation stages for matching the resonance frequency of the cavity to the radio frequency of acousto-optic modulator. The QML pulses with envelope durations of 100n150 ns and 100% modulation depth were observed for wide range of pump powers and repetition rates. In the preliminary experiments up to 3 W of output average power, 100 µJ of the envelope energy, having approximately 5n8 mode locked pulses were achieved.
4
Content available remote Spectral and generation characteristics of YAG:Nd³⁺ crystals with high concentration of Nd³⁺ ions
51%
Mierczyk Z. , Kopczyński K. , Żendzian W. , Łukasiewicz T.
Opto-Electronics Review
|
2001
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tom Vol. 9, No. 1
83-90
EN
The paper presents investigation results of optical, spectroscopic, and generation parameters of YAG:Nd³⁺ with higher concentration of Nd³⁺ ions (1.1–1.8 at. % Nd³⁺). YAG:Nd³⁺ single crystals were obtained by the Czochralski method. Investigations on optical quality were carried out using elastoscopic and interferometric methods. Absorption spectra within the spectral range of 200–3000 nm (∆ʎ = 1 nm) and pumping range of 750-850 nm (∆ʎ = 0.1 nm) were determined. Also the spectra of luminescence induced with radiation emitted by a laser diode of 808 nm were investigated and lifetime of Nd³⁺ ions in the upper laser level (⁴F₂/₃) was determined. In the all investigated crystals, doped up to 1.3 at.% Nd³⁺, the time of fluorescence decay from ⁴F₂/₃ level is 230 us. It was stated that high level of Nd³⁺ ions doping (above 1.33 at. % Nd³⁺) causes reduction of lifetime of the upper level ⁴F₂/₃ as a result of concentric quenching of luminescence. For the crystals of 1.8 at. % Nd³⁺ concentration, upper laser level lifetime has been educed to 183 us. Also the results of generation investigations obtained in a laser system with the examined YAG:Nd active media in form of side pumped "slabs" and inform of longitudinally pumped rod.
5
Content available remote Investigation on passively Q-switched Nd:YAG slab laser pumped by 2D quasi cw diode laser stack
51%
Żendzian W. , Jabczyński J. K. , Mierczyk Z.
Opto-Electronics Review
|
2001
|
tom Vol. 9, No. 1
75-81
EN
The paper presents results of investigations on generation of Nd:YAG triangle slab laser pumped by 2D diode array. The pump beam shape quality with respect to pump/mode overlap efficiency was investigated both theoretically and experimentally. Two cavity schemes with and without pump forming optics were verified in free running and passively Q-switching modes. Slope efficiency of 45% and output energy of 24 mJ for incident 60 mJ of pump energy were achieved in free running mode. Applying Cr⁴⁺:YAG crystal as passive Q-switch, the output energy of 5 mJ and 0.5 MW peak power were obtained in the optimised resonator.
6
Content available remote Measurement of Q-Switching & Mode Locking in diode pumped Nd:YVO₄ laser with passive saturable absorbers
51%
Kwiatkowski J. , Jabczyński J. K. , Żendzian W.
Biuletyn Wojskowej Akademii Technicznej
|
2005
|
tom Vol. 54, nr 11
35-41
EN
The saturable absorbers (Cr⁴⁺:YAG, GaAs and LiF crystals for 1064 nm wavelength, V³⁺:YAG crystals for 1340 nm respectively) were examined as passive Mode Lockers and Q-switches in diode pumped Nd:YVO₄ lasers in the Z-type resonators. In each case, partially modulated long trains of QML pulses were observed. As a rule, envelopes with about 1 µs duration and more than 50% depth of modulation were observed. For stabilization of the mode locking trains the nonlinear crystals (KTP or LBO) as negative feedback elements were inserted. The fully modulated QML trains for intracavity II harmonic conversion at 670 nm wavelength in V³⁺:YAG Q-switched Nd:YVO₄ laser with LBO crystal were demonstrated.
PL
W artykule przedstawiono wyniki badań lasera Nd:YVO₄ pracującego w konfiguracji rezonatora typu "Z" z pasywnymi modulatorami dobroci (Cr⁴⁺:YAG, GaAs oraz LiF na długości fali generacji 1064 nm, V³⁺:YAG na dlugości fali 1340 nm). Obserwowano impulsy laserowe z synchronizacją modów o czasie trwania obwiedni około 1 µs i głębokości modulacji powyżej 50%. W celu polepszenia stabilności synchronizowanych modów jako ujemne sprzężenie wykorzystano nieliniowy element w postaci kryształu KTP lub LBO. Zaobserwowano pełną głębokość modulacji promieniowania o długości fali 670 nm w laserze Nd:YVO₄ z przełącznikiem dobroci V³⁺: YAG z przetwarzaniem na II harmoniczną za pomocą kryształu LBO.
7
Content available remote Generator parametryczny pompowany wewnątrz rezonatora lasera Nd:YAG z pasywną modulacją dobroci
51%
Żendzian W. , Jabczyński J. K. , Kwiatkowski J.
Biuletyn Wojskowej Akademii Technicznej
|
2002
|
tom Vol. 51, nr 6
5-20
PL
W artykule przedstawiono ednorezonansowy generator parametyczny z kryształem KTP pompowany wewnątrz rezonatora lasera Nd:YAG z pasywną modulacją dobroci pobudzanego 300 W diodą quasi ciągłego działania. Uzyskano ze sprawnością całkowitą 3,8% impulsy na długości fali 'Bezpiecznej dla wzroku" ʎ = 1572nm, o energii 1,9 mJ i czasie trwania 2,8 ns, generowane z częstotliwością 100 Hz. Przedstawiono również model teoretyczny wewnątrzrezonatorowo pompowanego generatora parametrycznego IOPO, bazujący na równaniach kinetycznych lasera z pasywnym modulatorem dobroci rezonatora i równaniach kinetycznych generatora parametrycznego. Uzyskano dobrą zgodność wykonanych obliczeń przebiegów czasowych generacji IOPO z wynikami eksperymentalnymi. Zarówno eksperymentalnie, jak i teoretycznie wykazano dużą prawność IOPO.
EN
It is presented a single resonance parametric generator with KTP crystal pumped in the intracavity of Nd:YAG laser with Q-factor passive modulation. The generator was excited using 300 W quasi-continuous operated diode. The pulses were obtained of 3,5% total effeciency and eyesafe wavelenght ʎ = 1572 nm of energy 1.9 mJ and duration 2.8 ns generated with frequency 100 Hz. A theoretical model of the intracavity pumped the IOPO parametric generator is also presented based on the kinetic equations of the laser with passive modulator of cavity Q-factor and kinetic equations of parametric generator. A good coincidence of the time courses of the IOPO generation with experimental results is obtained. alarge efficiency of the IOPO was found in the experiments as well as theoretically.
8
Content available remote CW mode locked Nd:YVO₄ laser pumped by 20-W laser diode bar
51%
Jabczyński J. K. , Żendzian W. , Kwiatkowski J.
Opto-Electronics Review
|
2006
|
tom Vol. 14, No. 2
135-139
EN
The efficient cw mode locking (cw-ML) regime was demonstrated in Nd:YVO₄ laser by means of saturable absorber mirror (SAM). The 0.3-at.% Nd³⁺ doped 10-mm-long YVO₄ crystal end pumped by 20-W diode module with a beam shaper was applied as a gain medium located in the close vicinity to the rear flat mirror of the first arm of Z-type resonator of 316 cm total length with two curved mirrors of 100-cm curvature radii. The SAM of 2%-saturable absorptance and saturation fluence of 50 μJ/cm² was mounted at the opposite end of a resonator. The developed “dynamically stable” cavity design mitigates detrimental role of thermal aberration in gain medium, enforcing clean perfect mode locking even for the highest pump densities. The cw-ML pulses with 47.5 MHz repetition rate and pulse durations in the range of 15–20 ps were observed for a wide range of pump powers and output coupler losses. In the best case, for 32% of output coupler transmission, up to 6.2 W of average power with near 35% slope efficiency was achieved. The thresholds for Q-switched ML, cw-ML regimes were 2.67 W and 6.13 W of pump power, respectively. For the maximum pump power of 20 W we obtained 133 nJ of pulse energy with 16-ps pulse duration, resulting in a peak power higher than 8 kW. The threshold energy density at SAM giving the QML regime was estimated to be about 30 μJ/cm2, threshold of cw-ML regime was 220 μJ/cm².
9
Content available remote Laser beam propagation in gain media of diode pumped lasers
51%
Jabczyński J. K. , Kwiatkowski J. , Żendzian W.
Optica Applicata
|
2003
|
tom Vol. 33, nr 2-3
411-420
EN
Two models of gain and thermal guiding effects were derived. In the first one, the complex ABCD matrix for a crystal under gain and thermal guiding was applied to describe the operation of microchip near threshold. In the second one, a simple iterative procedure was proposed to calculate effective fundamental mode parameters of a cavity under thermal and gain guiding for given bare cavity ABCD matrix and pumping parameters, including gain saturation, passive cavity losses and reabsorption ones. The influence of gain guiding effects causes changes of waist width in the range up to 50% compared to expectations derived from thermal guiding theory. Application of such a method for resonators of passively Q-switched lasers was proposed. Results of calculations for microchips were verified with experiment.
10
Content available remote Optical characterization of diode side pumped active elements
51%
Jabczyński J. K. , Kwiatkowski J. , Żendzian W.
Optica Applicata
|
2003
|
tom Vol. 33, nr 2-3
421-431
EN
A numerical model of side pumped gain elements of rod or slab shape enabling estimation of overlapping efficiency and threshold was developed. This model was applied for analysis and optimization of laser heads side pumped by a single diode bar. The diode side pumped lasers heads for Nd:YAG rod and slab active elements were designed and characterized under real pumping conditions with a 40-W diode bar. The optical performance of both types of heads was shown experimentally to be delimited by transversal, asymmetrical thermal gradients resulting in high level of depolarization and diffraction losses. The fundamental mode limit is about 20 W per 1 cm for a head side pumped by a single diode bar
11
Content available remote Intracavity optical parametric oscillator pumped by passively Q-switched Nd:YLF laser
51%
Żendzian W. , Jabczyński J. K. , Kwiatkowski J.
Opto-Electronics Review
|
2009
|
tom Vol. 17, No. 1
45-52
EN
We report on a passively Q-switched end pumped Nd:YLF laser including a noncritically phase-matched KTP singly resonant intracavity optical parametric oscillator (IOPO-KTP). For the Q-switching operation we have used Cr:YAG saturable absorber. The optimized passively Q-switched Nd:YLF laser without IOPO generated linearly polarized pulses of 11.5 ns and 1.07 mJ at 1047 nm. The conversion efficiency of the optimized Q-switched pulse energy at 1047 nm to 1547 nm of a signal approached about 47%. For optimizing both Nd:YLF laser and IOPO we have numerically solved a theoretical model. We have achieved 1.6-ns duration pulses at 1547 nm with energy of 0.5 mJ and peak power of above 300 kW. The beam quality was excellent (M ² ≈ 1).
12
Content available remote Application of Wigner transform for characterization of aberrated laser beams
51%
Jaguś J. , Jabczyński J. K. , Żendzian W. , Kwiatkowki J.
Optica Applicata
|
2005
|
tom Vol. 35, nr 1
33-41
EN
The slit scan method was implemented for registration of intensity profiles along the caustics of a laser beam. The inverse Radon transform of spatialy normalized intensity profiles enables direct computation of Wigner transform of real laser beam. The Rayleigh range, divergence angle, beam quality factor, global degree of coherence can be determined in such a simple way. A procedure enabling derivation of the shape of aberrated wavefornt and spherical aberration content was elaborated. This method was applied for investigation of the aberrated laser beams generated by cw and pulsed diode pumped laser.
13
Content available remote Thermo-optic effects in solid state lasers end-pumped by fiber coupled diodes
51%
Jabczyński J. K. , Jaguś J. , Żendzian W. , Kwiatkowski J.
Opto-Electronics Review
|
2005
|
tom Vol. 13, No. 1
69--74
EN
Review of thermo-optic effects in gain media of diode pumped lasers is presented. Methods of modelling and compensation of such effects are discussed. Results of characterization of end-pumped lasers by means of energetic and caustics measurement techniques are presented and discussed. Also application of Wigner distribution method for characterization of aberrated laser beams is discussed. Thermally induced astigmatism was observed for the anisotropic rods at high heat load.
14
Content available remote High repetition rate, V³⁺:YAG crystal Q-switched diode pumped Nd lasers
45%
Jabczyński J. K. , Mierczyk Z. , Żendzian W. , Kopczyński K. , Frukacz Z.
Opto-Electronics Review
|
2001
|
tom Vol. 9, No. 1
57-66
EN
The high repetition rate passively Q-switched neodymium host lasers operating at 1 mm wavelenght pumped by a 10-W fibre-coupled diode laser are presented. As a passive q-switch the V³⁺:YAG crystal was applied. The V³⁺:YAG parameters were determined in spectroscopic and saturable transmission experiments. A numerical model taking into account short recovery time of V³⁺:YAG ~ 5 ns and excited state absorption was used to analyse such a laser. The thermal lensing magnitude and performance were determined in free running experiments for two Nd:YAG rods of different quality and Nd:YLF crystal. The smooth Q-switched pulses with repetition rates of 40-200 kHz were abtained in short linear cavities of a length less than 11cm. The highest average power of 1.4 W with slope efficiency of 20% was demonstrated in Nd:YAG laser. Long pulse durations of hundreds ns and low pulse energy of a few mJ (up to 24 in the best case) were caused by low value of the ratio of the absorption cross section of V³⁺:YAG to emission cross section of Nd:YAG. The much higher pulse energy of 70 µJ with pulse duration of 80 ns was abtained in lower gain Nd:YLF laser in a cavity of 140 mm length with internal lens 50 mm focal length.
15
Content available remote High repetition rate, tunable, Q-switched diode pumped Tm:YLF laser
38%
Gorajek Ł. , Jabczyński J. K. , Żendzian W. , Kwiatkowski J. , Jelinkova H. , Sulc J. , Nemec M.
Opto-Electronics Review
|
2009
|
tom Vol. 17, No. 4
309-317
EN
The aim of work was to characterize a simple oscillator consisted of Tm:YLF crystal end-pumped by a fiber coupled diode laser and active Q-switch with tunability option. About 7 W with near 35% slope efficiency was demonstrated in a free-running mode. The divergence angle was about 4.3 mrad and estimated parameter M² < 1.3. Continuous tuning by means of Lyot's filter, consisted of 2 quartz plates in the range of 1879.0-1939.4 nm with less than 1-nm linewidth, was achieved. For the best case (10-ms pump pulse duration, 42-A pump current corresponding to 266 mJ of pump energy) , the Q-switched energy was 10.5 mJ with pulse duration of 22 ns corresponding to near 0.5 MW peak power. The 2.5 W of average power with 12.6-kW peak power and 2000-Hz repetition rate was demonstrated for cw pumping regime.
16
Content available remote Preparation and characterization of transparent Nd:YAG ceramics
32%
Librant Z. , Jabczyński J. K. , Węglarz H. , Wajler A. , Tomaszewski H. , Łukasiewicz T. , Żendzian W. , Kwiatkowski J.
Opto-Electronics Review
|
2009
|
tom Vol. 17, No. 1
72-77
EN
Transparent Nd:YAG ceramics were produced by solid.state reaction of high.purity (4N) nanometric oxides powders, i.e., Al₂₃O₃, Y₂₃O₃ and Nd₂₃O₃. After sintering, mean grain sizes of 2% Nd:YAG samples were about 20 µm and their transparency were a bit worse than that of 0.9% Nd:YAG single crystal. Two types of active elements: rods and slabs were fabricated and characterized in several diode pumping schemes. In end pumping configuration as a pump source 20.W fiber coupled laser diode operating in low duty cycle regime (1 ms pump duration/20 Hz) was deployed. In the best case, 3.7 W of output power for 18 W of absorbed pump power, M ² < 1.4 were demonstrated for uncoated ceramics Nd:YAG rod of Φ 4×3mm size in preliminary experiments. For the ceramics of two times lower Nd dopant level above 30% slope efficiency was achieved. In case of Nd:YAG ceramic slab side pumped by 600.W laser diode stack above 12 W was demonstrated with slope efficiency of 3.5%.
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