Q-switched Intracavity Raman Laser Research Articles

Analysis of actively Q-switched infrared Raman lasers with crystalline media of multi-Raman-modes

Actively Q-switched intracavity Raman lasers can generate multi-wavelength infrared laser based on rich modes of crystalline Raman media. Assuming the intracavity photon densities and initial population inversion densities to be of Gaussian spatial distributions, the space-dependent rate equations of actively Q-switched intracavity Raman lasers with two Raman modes are deduced. The rate equations are solved numerically to investigate the influences of normalized variables on pulse energy, peak power, pulse duration, and conversion efficiency of Raman laser outputs, respectively. There are obvious discrepancies between the results of two Raman modes. The dependence of Raman laser conversion efficiency at 1103 nm on normalized initial population inversion density is numerically calculated, the experimental results are consistent with the numerical ones, and the optimum conditions are proposed theoretically in the end.

Simultaneous three Raman shift passively Q-switched intracavity Raman laser based on the overlapping Raman shift of 259 cm−1 in c-cut GdVO4 and YVO4

A diode-pumped passively Q-switched intracavity Raman laser is experimentally investigated, in which a c-cut Nd:GdVO4 crystal is used as a self-Raman medium and a c-cut Nd:YVO4 crystal is only used as a Raman medium. Simultaneous laser pulse outputs at 1096, 1176, 1177 nm corresponding to the first-Stokes light at 259, 882 and 890 cm−1 are acquired. 1128 nm light corresponding the second-Stokes light at 259 cm−1 is obtained and occupies the majority of the output power. The Stimulated Raman Scattering at 259 cm−1 takes place in both the GdVO4 and the YVO4 crystals. With an incident pump power of 7.74 W and a pulse repetition frequency of 30.5 kHz, the average output powers at 1096, 1128, 1176 and 1177 nm are 47.6, 446, 27 and 44.2 mW, respectively.

主动调Q腔内和频拉曼激光器的数值模拟

The normalized rate equations of the LD pumped actively Q-switched intracavity sum-frequency Raman laser were deduced, and the reasonable value scope of seven comprehensive factors of the rate equations was estimated respectively according to the parameters of typical experimental setups. The influences of the comprehensive factors on the laser output peak power, single pulse energy and pulse width were researched by the numerical simulation of the actively Q-switched intracavity sum-frequency Raman laser. It was found that there was a matching relation between the normalized sum-frequency factor F and the normalized Raman gain coefficient M, and the matching equations and curves of F and M at different inversion population density N were obtained by making use of the method of numerical fitting, the result demonstrates that the matching values of F and M are basically linearly related, which can be employed to guide the optimization of parameters of the length of Raman medium and sum-frequency crystal in the experiment to accomplish the high efficient sum-frequency laser. Finally, the results are used to calculate and analyze the reported experiment to optimize the parameters of setups to gain higher output power and more efficient laser.

LD泵浦被动调Q腔内和频拉曼激光器速率方程

LD泵浦被动调Q腔内和频拉曼激光器速率方程

High-efficiency eye-safe Nd:YAG/SrWO4 Raman laser operating at 1664 nm

A high-energy diode-pumped actively Q-switched intracavity Raman laser with SrWO4 as the Raman active medium is demonstrated. By employing ceramic Nd:YAG laser operating at 1444 nm as pump source, first-Stokes Raman generation at 1664 nm is achieved. With a pump power of 27.7 W, a maximum output power of 1.16 W was obtained at a pulse repetition rate of 10 kHz, corresponding to an optical conversion efficiency of 4.2 %. The maximum pulse energies of as high as 266, 150.5, 189 and 116 µJ were achieved at the pulse repetition frequency of 1, 2, 5 and 10 kHz.

Eye-safe actively Q-switched diode-pumped lasers with intracavity Raman conversion in YVO4, KGd(WO4)2, PbWO4, and Ba(NO3)2 crystals

We have investigated the self-Raman and intracavity Raman frequency conversion of the end-diode-pumped acoustooptic Q-switched Nd:YVO4 laser radiation to eye-safe radiation. The 1st Stokes oscillation in YVO4 (Nd:YVO4), KGd(WO4)2, PbWO4, and Ba(NO3)2 crystals excited by the laser radiation at a wavelength of 1342nm permits obtaining oscillations at 1524, 1496 or 1527, 1527, and 1562nm wavelengths, respectively. We have obtained pulsed lasing with a repetition rate of 2–20kHz, an output energy of 37–95µJ, and a duration of 6–8ns. We propose a model of the actively Q-switched intracavity Raman laser taking into account the real switching off/on times of the actively Q-switch and the excited state absorption in the active medium. We used this model to simulate the dynamics of the self-Raman Nd:YVO4 laser. The proposed model gives results that agree fairly well with the experimental data.

Four-wavelength laser based on intracavity BaWO₄ Raman conversions of a dual-wavelength Q-switched Nd:YLF laser.

By using diode-end-pumped acousto-optically Q-switched intracavity Raman laser configurations, we demonstrate a four-wavelength laser emitting at 1047.0, 1053.0, 1159.4 and 1166.8 nm. Two Nd:YLiF₄ crystals are employed to generate 1047.0-nm and 1053.0-nm laser radiations. These two lasers are then frequency converted by a BaWO₄ Raman crystal to generate 1159.4-nm and 1166.8-nm first-Stokes waves. With pulse synchronization realized, we obtain the maximum output powers of 427, 418, 423 and 332 mW for 1047.0-nm, 1053.0-nm, 1159.4-nm and 1166.8-nm lasers, respectively. The total optical-to-optical conversion efficiency is 15.1%.

Theoretical and experimental study on passively Q-switched intracavity frequency-doubled solid-state yellow Raman lasers

Normalized space-dependent rate equations of passively Q-switched intracavity frequency-doubled Raman lasers are deduced for the first time. The normalized rate equations are solved numerically to investigate the influences of the normalized variables on the yellow laser performance. The LD end-pumped passively Q-switched Nd:YAG/SrWO(4)/KTP/Cr:YAG yellow Raman laser is realized, and the maximum yellow laser output power is 350 mW with the incident pump power of 5.9 W with Cr:YAG of 85% initial transmission. The theoretical analysis and optimization are taken out for the experiment, and the theoretical results are in accordance with the experimental ones.

Experiments with an intracavity BaTeMo2O9 Raman laser

A diode-side-pumped actively Q-switched intracavity Raman laser emitting at 1178 nm employing Nd:YAG as the gain medium and BaTeMo2O9 as the Raman medium is realized. With a pump power of 115 W and pulse repetition rate of 10 kHz, a maximum first-Stokes output power of 1.9 W is obtained. The corresponding diode-to-first-Stokes conversion efficiency is 1.7% and the first-Stokes pulse width is 35 ns. The preliminary experiments proved that an intracavity BaTeMo2O9 Raman laser is feasible.

Diode-pumped actively Q-switched Tm, Ho:GdVO_4/BaWO_4intracavity Raman laser at 2533 nm

A compact diode-end-pumped actively Q-switched intracavity Raman laser with Tm,Ho:GdVO(4) laser gain medium and BaWO(4) Raman gain crystal is demonstrated for the first time. The Raman threshold is as low as 2.0 W of diode power at 802 nm. The highest average output power of 186 mW at the first Stokes wavelength of 2533 nm is obtained at a pulse repetition rate of 1 kHz, and a pump power of 2.8 W, corresponding to a diode-to-Stokes optical conversion efficiency of 6.6%. The pulsewidth and pulse energy are 7.8 ns and 0.19 mJ, respectively.

A compact passively Q-switched SrWO4 Raman laser with mode-locked modulation

A compact all-solid-state diode-pumped passively Q-switched intracavity SrWO4 Raman laser was constructed with a simple linear cavity and a Cr:YAG crystal as the saturable absorber. A diode-to-Stokes conversion efficiency of 12.7% was obtained at a pump power of 6.3 W, which was much higher than those of previously reported diode-pumped passively Q-switched intracavity Raman lasers. In the stimulated Raman scattering operation, mode-locked modulation was observed in the Q-switched envelope; the mechanism of the mode locking is also discussed.

Diode-Pumped Eye-Safe Intracavity Raman Laser with Ceramic Nd:YAG Gain Medium and BaWO<sub>4</sub> Raman Crystal

A diode-pumped actively Q-switched eye-safe intracavity Raman laser with ceramic Nd:YAG gain medium and BaWO4 Raman crystal is demonstrated for the first time. The highest average output power of 0.76 W is obtained at a pulse repetition frequency of 30 kHz and a pump power of 11.3 W. The corresponding conversion efficiency from the diode pump power to Raman output power is 6.7%. The highest pulse energy of 38.1 µJ is obtained at a pulse repetition frequency of 15 kHz and a pump power of 7.8 W, and the corresponding peak power is 4.9 kW.

Diode-pumped passively Q-switched Nd:YAG/SrWO4 intracavity Raman laser with high pulse energy and average output power

A diode-pumped passively Q-switched Nd:YAG/SrWO4 intracavity Raman laser is presented. As high as 1.78 W average power is obtained at an incident pump power of 14.9 W with a pulse repetition frequency of 21.2 kHz. The highest pulse energy is 88.1 μJ obtained at a pump power of 13.7 W. The obtained pulse energy and average power are much higher than those of the previously reported diode-pumped passively Q-switched intracavity Raman lasers.

Analysis of actively Q-switched intracavity frequency-doubled solid-state yellow Raman lasers

The actively Q-switched solid-state yellow Raman laser with intracavity frequency doubling has attracted extensive research due to its high efficiency, simplicity and compactness. In this paper, the normalized space-dependent rate equations of this kind of lasers are deduced and analyzed to illustrate the effects of the composite variables on the yellow-laser performance, and several general curves are generated. The optimized values of the composite parameters are analyzed for the efficient yellow-laser output. In the end, application examples are given to shown that these theoretical results can predict the performance of actively Q-switched intracavity frequency-doubled solid-state yellow Raman lasers effectively.

Self-frequency-doubled KTiOAsO_4 Raman laser emitting at 573 nm

A self-frequency-doubled KTiOAsO4 (KTA) Raman laser is realized in a diode-end-pumped acousto-optically Q-switched intracavity Raman laser configuration. A 30-mm-long x-cut KTA crystal is used as the Raman medium, and its 671 cm(-1) Raman mode is employed to finish the conversion from 1064 nm fundamental laser to 1146 nm Raman laser. Self-frequency doubling of the Raman laser is accomplished in the same KTA crystal, and a 573 nm yellow laser is obtained. With an incident diode power of 10.9 W and a pulse repetition rate of 20.8 kHz, a yellow-laser power of 0.82 W is obtained. The conversion efficiency from diode power to yellow-laser power is 7.5%.

Highly efficient diode-pumped actively Q-switched Nd:YAG-SrWO_4 intracavity Raman laser

A highly efficient diode-pumped actively Q-switched intracavity Raman laser with SrWO(4) as the Raman-active medium is presented. As high as 23.8% diode-to-Stokes optical conversion efficiency is obtained with an incident pump power of 7.17 W and a pulse repetition rate of 15 kHz.

Modeling of Actively $Q$-Switched Intracavity Raman Lasers

The normalized space-dependent rate equations are deduced assuming the intracavity photon densities and initial population-inversion density to be of Gaussian spatial distributions in the diode-pumped actively Q-switched intracavity Raman lasers. Numerical calculations are carried out to investigate the influences of these normalized variables on the pulse parameters of the first Stokes. The rate equations under the planewave approximation are also normalized and solved numerically, and the results show the obvious discrepancies from those of the space-dependent theory. The spontaneous Raman scattering factor in rate equations are deduced in detail for the first time, and the oscillating threshold of the first Stokes inside the resonator is deduced analytically. A sample calculation for an actively Q-switched self-Raman laser is presented to demonstrate the use of the curves and related formulas.

Numerical modelling of passively Q-switched intracavity Raman lasers

Assuming intracavity photon densities to be of Gaussian spatial distributions, the space-dependent rate equations of passively Q-switched intracavity Raman lasers are deduced for the first time for the pumping beams of Gaussian and top-head spatial distributions, respectively. The new rate equations are normalized and solved numerically to investigate the influences of the normalized initial population inversion density, normalized Raman gain coefficient, saturable absorber parameter, beam size ratio of pump to fundamental laser and loss ratio of the first Stokes to fundamental laser on the pulse parameters of the first Stokes. The results of the Gaussian and top-head pumpings show similar trends despite some discrepancies. The new theories and numerical results will help design passively Q-switched intracavity Raman lasers of high performance.

Crystalline Raman Lasers

In this paper, we review the developments of crystalline Raman lasers over the past five years. Average powers exceeding 5 W and pulse energies above 1 J in the near infrared have been demonstrated for larger scale devices. There has been a rapid development of all-solid-state sources based on the standard diode-pumped lasers, especially intracavity crystalline Raman lasers, which offer wavelength versatility at high conversion efficiencies (overall diode Stokes optical conversion efficiencies up to 17%) in the near infrared, including the 1.5- mum eye-safe band. Passively Q-switched intracavity Raman lasers based on self-Raman laser materials offer many advantages for miniaturization of short-pulse (1 ns) sources. Intracavity frequency-doubled crystalline Raman lasers have also emerged as practical and versatile sources in the yellow orange region at 1-W power levels with diode-visible efficiencies near 10%. Recent developments of all-solid-state continuous-wave (CW) intracavity crystalline Raman lasers offer many possibilities for the future: intracavity frequency doubling has already resulted in the demonstration of CW visible sources with powers approaching 1 W at 5% diode-visible efficiency.

Theoretical and Experimental Study on the Self-Raman Laser With<tex>$hbox Nd:YVO_4$</tex>Crystal

The intracavity photon densities and the initial population inversion density were assumed to be Gaussian distributions in the rate equations of the laser diode end-pumped actively Q-switched intracavity Raman laser. These space-dependent rate equations were solved numerically. In the experiment, an efficient self-Raman laser was realized based on the multifunctional Nd:YVO4 laser crystal with the acoustooptic Q-switch. The output, temporal, and spectral characteristics of the self-Raman laser were investigated experimentally in detail. The performance of the self-Raman laser was studied numerically, and the theoretical results showed the main trends of the intracavity Raman laser, which are in agreement with the experimental ones