Saturable Absorber Cr(4)+:(Sr, Ca)Gd(4)(SiO(4))(3)O Crystals as Q Switches for a Diode-Pumped Nd(3)+:KGd(WO(4))(2) Laser

Passive Q switching of a diode-pumped Nd(3+):KGd(WO(4))(2) laser is demonstrated by use of Cr(4+):SrGd(4)(SiO(4))(3)O and Cr(4+):CaGd(4)(SiO(4))(3)O crystals as saturable absorbers. An average output power of 40 mW was obtained with a pulse repetition rate of ~0.4 MHz.     

Monoblock laser for a low-cost, eyesafe, microlaser range finder

A small, lightweight, low-cost prototype laser has been developed for use in a microlaser range finder (muLRF). The laser design is based on a flash-lamp-pumped, Nd:YAG laser with a Cr(4+) passive Q switch. The design incorporates a monolithic potassium titanyl arsenide (KTA) optical parametric oscillator (OPO) in an intracavity configuration, producing output at 1.54 mum. Precisely cut, properly coated crystals make up the laser resonator, reducing the number of components and enabling laser oscillation with the simplest of alignment fixtures. The 1.54-mum laser cavity consists of only four rectangular-shaped crystals: a Nd:YAG laser rod, a Nd:YAG endcap, a Cr(4+) Q switch, and a KTA OPO. Along with a ceramic laser pallet and a flash lamp, these six components make up a prototype monoblock (essentially a one-piece) laser transmitter. Several of these simple prototypes have been built and tested, giving a nominal output of >3.0 mJ at 1.54 mum with a 27-ns pulse width. The transmitter was incorporated into a breadboard laser range finder, and successful ranging operations were performed to targets at ranges in excess of 3 km.     

Numerical study of passive Q switching of a Tm:YAG laser with a Ho:YLF solid-state saturable absorber

In a previous work [Appl. Phys. Lett. 65, 3060 (1994)] we experimentally demonstrated that passive Q switching of a 2,017-nm, flashlamp-pumped Tm,Cr:YAG laser with a Ho:YLF saturable absorber could be obtained with an internal focusing lens. We numerically investigate the optical performance of the Ho:YLF Q-switched Tm:YAG laser system by solving the coupled rate equations. The simulation results indicate that the results obtained numerically are in good agreement with those obtained experimentally. With typical laser configuration, a Q-switched laser pulse of 35 mJ in 30 ns is obtained.     

Chromium-doped LiCAF laser passively Q switched with a V3+:YAG crystal

A tunable, lamp-pumped Cr(3+):LiCaAlF(6) laser that operates in the 760-800-nm wavelength range is demonstrated. As a passive Q switch the V(3+):YAG crystal, characterized by wide saturable absorption in the 760-900-nm wavelength range, was applied. The V(3+):YAG parameters were determined by spectroscopic and saturable transmission measurements. The 30-mJ output energy at 2-Hz repetition rate in the free-running regime was obtained in a cavity reinforced by a diaphragm near the fundamental mode. The dispersive prism inserted into the cavity enabled tuning in the 760-800-nm wavelength range. In the passive Q-switching regime we achieved greater than 1-mJ energy with 50-ns pulse duration in a 35-cm-long cavity. A numerical model that takes into account the short recovery time of V(3+):YAG (~5 ns) and excited-state absorption was used to analyze such a laser.     

Efficient continuous-wave radiatively cooled cr(4+):forsterite lasers at room temperature

Results of a detailed experimental investigation aimed at reducing the thermal loading problem in a cw Cr(4+):forsterite laser at elevated temperatures are presented. From a Cr(4+):forsterite crystal with a differential absorption coefficient of 0.57 cm(-1), as much as 900 mW of cw output power has been obtained at 1.26 mum and at a crystal boundary temperature of 15 degrees C with an absorbed pump power of only 4.5 W at 1.06 mum. No chopping of the pump beam was necessary. An efficient radiative cooling technique was further employed to cool the laser and no subsequent power fading was observed. To the author's knowledge, the measured absorbed power slope efficiency of 29.5% represents the highest cw power performance reported to date from a Cr(4+):forsterite laser pumped by a Nd:YAG laser around room temperature. The role of the low differential absorption coefficient in the reduction of thermal loading is further elucidated by presenting comparative cw power performance data with a second Cr(4+):forsterite crystal having a differential absorption coefficient of 1.78 cm(-1) in the temperature range between 12 and 35 degrees C. Finally, some interesting multipulse effects of the laser observed in the millisecond regime during quasi-cw operation at 50% duty cycle are described.     

Passively Q-Switched Yb:YAG Laser with Cr(4+):YAG as the Saturable Absorber

By using a continuous-wave Ti:sapphire laser as a pumping source, we demonstrated a passively Q-switched Yb:YAG laser at room temperature with Cr(4+):YAG as the saturable absorber. We achieved an average output power of as much as 55 mW at 1.03 mum with a pulse width (FWHM) as short as 350 ns. The initial transmission of the Cr(4+):YAG has an effect on the pulse duration (FWHM) and the repetition rate of the Yb:YAG passively Q-switched laser. The Yb:YAG crystal can be a most promising passively Q-switched laser crystal for compact, efficient, solid-state lasers.     

Efficient quasi-continuous-wave and passively Q-switched laser operation of a Nd3+:BaGd2(MoO4)4 cleavage plate

Pumped by a Ti:sapphire laser at 807 nm, efficient quasi-cw and passively Q-switched laser operations have been realized from a 1.1 mm thick, 1.2 at. % Nd(3+):BaGd(2)(MoO(4))(4) cleavage plate in a plano-plano cavity. When the absorbed pump power was 1060 mW, the achieved maximum quasi-cw output power was 580 mW. The slope efficiency and absorbed pump threshold power were 60% and 50 mW, respectively. Using a Cr(4+):YAG crystal with an initial transmission of 85% as the saturable absorber, a pulse laser with 3.0 microJ energy, 30 ns duration, and 52 kHz repetition rate has been obtained when the absorbed pump power was 1060 mW. The polarization characteristic and laser spectra of both the quasi-cw and passively Q-switched lasers have been measured.     

Optimization of peak power of doubly Q-switched lasers with both an acousto-optic modulator and a Cr4+-doped saturable absorber

A doubly Q-switched laser can obtain a shorter pulse with a stable repetition rate and high pulse peak power, which has been experimentally proved. By taking into account the Gaussian spatial distributions of the intracavity photon density and the initial population-inversion density as well as the influence of the acousto-optic (AO) Q switch, we introduce the coupled rate equations for a doubly Q-switched laser with both an AO modulator and a Cr(4+)-doped saturable absorber. These coupled rate equations are solved numerically. The key parameters of an optimally coupled doubly Q-switched laser are determined based on maximizing the peak power, which include the optimal normalized coupling parameter, the optimal normalized saturable absorber parameters, and the normalized parameters of the AO Q switch. The optimal normalized peak power, the corresponding normalized energy, and the normalized pulse width are also given, and a group of general curves are generated for the first time to our knowledge. The curves can give us a good understanding of the dependence of the optimal key parameters on the parameters of the gain medium, the saturable absorber, the AO Q switch, the resonator, and the spatial distributions of the intracavity photon density. The optimal calculations for a diode-pumped Nd(3+):YVO(4) laser with both an AO modulator and a Cr(4+):YAG saturable absorber are presented to demonstrate the use of the curves and the related formulas.     

End-pumped 1.5 microm monoblock laser for broad temperature operation

We describe a next-generation monoblock laser capable of a greater than 10 mJ, 1.5 microm output at 10 pulses/s (pps) over broad ambient temperature extremes with no active temperature control. The transmitter design is based on a Nd:YAG laser with a Cr4+ passive Q switch and intracavity potassium titanyl phosphate optical parametric oscillator. To achieve the repetition rate and efficiency goals of this effort, but still have wide temperature capability, the Nd:YAG slab is end pumped with a 12-bar stack of 100 W (each) diode bars. Different techniques for focusing the pump radiation into the 4.25 mmx4.25 mm end of the slab are compared, including a lensed design, a reflective concentrator, and a lens duct. A wide temperature operation (-20 degrees C to 50 degrees C) for each end-pumped configuration is demonstrated.     

Numerical study of passive Q switching of a tunable alexandrite laser with a Cr:Y2SiO5 solid-state saturable absorber

Passive Q switching of a tunable alexandrite solid-state laser with a Cr:Y(2)SiO(5) solid-state saturable absorber is numerically studied over a major portion of the alexandrite tuning range. The theory of passive Q switching with a slowly relaxing saturable absorber is studied and utilized for evaluating the performance of the Cr:YSO Q-switched alexandrite laser system. With a typical laser configuration, a Q-switched laser pulse of 262 mJ in 23 ns is obtained.     

Performance of diode-end-pumped Cr, Nd:YAG self-Q-switched and Nd:YAG/Cr:YAG diffusion bonded lasers

Self-passively Q-switching of a diode-pumped Cr,Nd:YAG, where the Cr⁴⁺ is used as a saturable absorber for the 1064 nm laser emission is reported. The maximum average output power was obtained using an output coupler of R=86%. The self-Q-switched diode pumped laser yielded 1.86-W average output power with low threshold pumping power (≈1.7-W), average slope efficiency of ≈34%, pulse duration of about 14–16 ns, and modulation frequency ranging from 2.4 to 73 kHz, depending on the input pumping power. These results are the highest reported for self-Q-switched lasers. Higher slope efficiency (42%) and shorter Q-switched pulses were obtained for a Q-switched Nd:YAG/Cr⁴⁺:YAG diffusion bonded laser. A comparison of the codoped Cr,Nd:YAG laser performance, with that of a diffusion bonded laser is reported and analyzed.     

Passive Q Switching of a Diode-Pumped 946-nm Nd:YAG Laser with 1.6-W Average Output Power

As much as 1.6-W average output power was emitted in a simple setup from a diffusion-bonded Nd:YAG rod with 70-100-ns Q-switched pulses at 946 nm and repetition frequencies between 15 and 45 kHz at 22-W incident diode-pump power. A Cr(4+):YAG crystal with a bleachable loss of approximately 2.5% and a length of 0.5 mm was used as a saturable absorber. The extraction efficiency was 47% in comparison with the continuous-wave laser output power of 3.37 W in the free-running regime.     

Passively Q-Switched Diode-Pumped Continuous-Wave Nd:YAG-Cr(4+):YAG Laser with High Peak Power and High Pulse Energy

A high peak power and high pulse energy passively Q-switched diode-pumped cw Nd:YAG laser at 1.064-mum wavelength has been demonstrated with Cr(4+):YAG crystal as the saturable absorber. The average output power of 7-12 W and pulse duration of 100-250 ns was obtained with kilohertz repetition rates. The highest peak power and pulse energy obtained were 30 kW and 3.4 mJ, respectively. All the output resulted from the TEM(00) mode with M(2) < 1.1. The thermal lensing effect of the saturable absorber was investigated, demonstrating that it played an important role in optimization of the output.     

Q-switched 2-micron lasers by use of a Cr2+:ZnSe saturable absorber

Flash-lamp-pumped Ho:YAG (2090-nm) and Tm:YAG (2017-nm) lasers were, for the first time to our knowledge, passively Q switched by use of a Cr(2+):ZnSe saturable absorber. A Q-switched Ho laser with 1.3-mJ pulse energy and ~90-ns pulse duration and a Q-switched Tm laser with ~3.2-mJ pulse energy and 90-ns pulse duration were demonstrated. Compared with the free-running output energies at the Q-switching threshold pump levels, the Q-switching efficiencies were approximately 5% for the Ho:YAG laser and 16% for the Tm:YAG laser.     

Comparative experimental investigation of thermal loading in continuous-wave cr(4 +):forsterite lasers

Results of a detailed experimental study aimed at reducing the thermal loading effects in room-temperature continuous-wave Cr(4+):forsterite lasers are presented. By using a Nd:YAG pump laser operated at 1.06 mum, the effect of the absorption coefficient and crystal cross-sectional area on the power performance of three crystals was compared between 12 and 36 degrees C. Experiments indicated that a low differential absorption coefficient significantly reduces the pump-induced thermal effects and cavity losses that would otherwise give rise to inefficient operation and increased temperature sensitivity. In particular, a Cr(4+):forsterite crystal with an absorption coefficient of 0.57 cm(-1) yielded as much as 900 mW of output power at 1.26 mum and a crystal temperature of 15 degrees C with an incident pump power of only 7.6 W. To the author's knowledge, the demonstrated slope efficiency of 30% represents the highest continuous-wave power performance reported to date from this laser system at elevated temperatures.     

激光引信用微宝石激光器设计

针对微宝石激光器在激光引信领域的应用需求,从激光二极管泵浦Cr4 :YAG被动调Q微宝石激光器速率方程出发分析了输出镜反射率、Cr4 :YAG晶体初始透过率、泵浦速率对激光器输出参量的影响及其变化规律.理论计算表明,文中设计的激光器理论上可以实现短脉冲(＜1.5ns)、高峰值功率(14.5kW)、高重频(泵浦光为1W情况下激光重复频率为7.2kHz)的稳定激光输出.最后给出了Cr4 :YAG晶体运转过程,并以此为基础分析了微宝石激光器的稳定性.计算分析表明,微宝石激光器理论上可以满足激光引信用激光器的要求.     

Maximum value of the pulse energy of a passively Q-switched laser as a function of the pump power

The finite recovery time Ts of the bleached absorber is presented as one of the possible mechanisms accounting for the increase-maximum-decrease in pulse energy E with the pumping rate Wp in cw-pumped passively Q-switched solid-state lasers, by analytically evaluating the sign of the derivative partial differentialE/ partial differentialWP. The results show that, in the low pump regime (T>Ts, T is the interpulse period), the initial population density ni remains constant, the final population density nf decreases with Wp, and this results in a monotonic increase of E with Wp. In the high pump regime (T相似文献   

Diode-pumped Yb,Er:glass laser passively Q switched with a V3+:YAG crystal

Saturable-absorber Q switching of a diode-pumped erbium-doped glass laser at 1.54 microm with a V:YAG crystal has been demonstrated. An average output power of 30 mW with Q-switching efficiency of 37% and pulse duration of 350 ns have been obtained. Results of the numerical simulation of the laser have been presented.     

InGaAs quantum-well saturable absorbers for a diode-pumped passively Q-switched Nd:YAG laser at 1123 nm

A low-loss semiconductor saturable absorber based on InGaAs quantum wells was developed for highly efficient Q switching of a diode-pumped Nd:YAG laser operating at 1123 nm. With an incident pump power of 16 W, an average output power of 3.1 W with a Q-switched pulse width of 77 ns at a pulse repetition rate of 100 kHz was obtained.     

Comparison on performance of passively Q-switched laser properties of continuous-grown composite GdVO4/Nd:GdVO4 and YVO4/Nd:YVO4 crystals under direct pumping

The comparison on performance of passively Q-switched laser properties of continuous-grown composite GdVO(4)/Nd:GdVO(4) and YVO(4)/Nd:YVO(4) crystals under direct pumping to the emitting level was demonstrated. A Cr(4+):YAG crystal was used as saturable absorber. At an incident pump power of 10 W, the average output power, the pulse width, the repetition rate, the pulse energy, and the peak power for a GdVO(4)/Nd:GdVO(4) laser were 1.22 W, 48.1 ns, 121 kHz, 10.1 μJ, and 209.6 W, respectively. And for a YVO(4)/Nd:YVO(4) laser under the same conditions, these output characteristics were 1.26 W, 44.9 ns, 218 kHz, 5.8 μJ, and 128.7 W, respectively.