Compact and high-energy diode-side-pumped Q-switched Nd:YAG slab laser system for space application

We develop a compact and high-energy Nd：YAG slab laser system consisting of an oscillator and an amplifier for space applications. The oscillator is a diode-side-pumped electro-optically Q-switched slab laser with a cross-Porro resonator. The KD＊P Pockels cell with a low driving voltage of 950 V is used to polarization output coupling. The amplifier is a Nd：YAG zigzag slab pumped at bounces. The maximum output pulse energy of 341 m3 with 13 ns pulse duration is obtained from the system at the repetition rate of 20 Hz and the beam quality factors are M2=3.1 and M2=3.5. The beam pointing stabilities of the laser system are 3.05μrad in the X-direction and 3.99 grad in the Y-direction, respectively.     

Graphene-based passively Q-switched diode-side-pumped Nd:YAG solid laser

In this paper, a desirably simple, convenient and inexpensive saturable absorber mirror has been fabricated based on graphene, which has no wavelength selectivity. Moreover, there are no changes in the structure and characteristics of graphene. By inserting the graphene-PMMA SA mirror to the Nd: YAG laser, the shortest pulse width of 260 ns can be obtained with the single-pulse energy of about 8.32 μJ. The experimental results prove that our graphene-PMMA SA mirror is feasible and suitable for Q-switched lasers.     

Pre-pumped passively Q-switched Nd:YAG/Cr:YAG microchip laser

A pre-pumped passively Q-switched Nd:YAG/Cr:YAG microchip laser is demonstrated with a peak power of 7.5 kW at pulse repetition rate of serveral kilohertzs. The full-width at half-maximum(FWHM)is 734 ps, and the pulse energy is 5.5 μJ with a fundamental spatial mode. In this system, the pre-pumped microchip laser of Nd:YAG/Cr:YAG wafer which is bonded through the thermal-bonding technique has achieved a time jitter value of 12 μs and a Q-switched amplitude instability of 1.26％(15)through the pre-pumped modulation technique.     

高平均功率调Q准连续Nd:YAG激光器

通过选用低掺杂浓度的Nd:YAG晶体棒、热近非稳腔优化设计、双棒串接热致双折射补偿技术以及双Q开关正交放置结构，在LD抽运功率1116W时，实现调Q准连续全固态Nd:YAG激光器1064nm输出，平均功率达258W，光束质量M²～15.5，重复频率为10kHz，脉冲宽度为64ns，峰值功率达0.4GW，光光转换效率达23.1%. 关键词： Nd:YAG激光器 准连续波 激光二极管抽运 固体激光器     

Single-mode high-peak-power passively Q-switched diode-pumped Nd:YAG laser

We have demonstrated an efficient, compact, passively Q-switched single-mode diode-pumped Nd:YAG laser that uses Cr(4+):YAG as a saturable absorber. Linear- and ring-cavity configurations were demonstrated. Pulse energies and widths were, respectively, 1.5mJ and 3.9ns for the linear cavity and 2.1mJ and 12ns for the ring cavity.     

A thermally-insensitive passively Q-switched Cr:YAG/Nd:YAG laser

A passively Q-switched laser with Cr⁴⁺:YAG/Nd:YAG composite crystal using a corner cube prism cavity has been realized, in which the corner cube prism is the key element as it aids the compensation of the thermal lens effect of laser crystal. Compared with plane–plane mirror cavities under the same conditions, the stability of the laser performance using the corner cube prism cavity was improved remarkably over temperatures ranging from −40 to 65 °C. The decrease of Nd:YAG stimulated emission cross section with temperature was considered to be the main reason for the increase of average output pulse energy under the same cycle for the two different cavities when the ambient temperature changed −40 to 65 °C. The mode properties produced by the prism cavity were analyzed, and the theoretical results were verified by experimental observations.     

Experimental study of electro-optical Q-switched pulsed Nd:YAG laser

We report the specification of a compact and stable side diode-pumped Q-switched pulsed Nd:YAG laser. We experimentally study and compare the performance of the pulsed Nd:YAG laser in the free-running and Q-switched modes at different pulse repetition rates from 1 Hz to 100 Hz. The laser output energy is stabilized by using a special configuration of the optical resonator. In this laser, an unsymmetrical concave-concave resonator is used and this structure helps the mode volume to be nearly fixed when the pulse repetition rate is increased. According to the experimental results in the Q-switched operation, the laser output energy is nearly constant around 70 mJ with an FWHM pulse width of 7 ns at 100 Hz. The optical-to-optical conversion efficiency in the Q-switched regime is 17.5%.     

Nd:YAG调Q激光器双波长振荡机理分析

根据速率方程,研究了二镜腔Nd:YAG双波长调Q激光的振荡机理.通过分析不同透过率下的竞争过程,研究了双波长激光振荡的特点.研究结果表明,在调Q过程中1319nm激光的调Q脉冲起振时间滞后于1064nm激光,并且其最终调Q脉冲来自调Q之后的第一个弛豫振荡尖峰,是该弛豫振荡抑制掉其他弛豫振荡后的结果.通过振荡机理分析,得到了双波长脉冲输出能量相当的透过率条件. 关键词： 双波长 调Q激光 速率方程 弛豫振荡     

Output performance of thermally-insensitive passively Q-switched Nd:YAG laser

We study a Cr⁴⁺:YAG Q-switched Nd:YAG laser with a thermally-insensitive corner-cube-prism cavity where the corner cube prism is the key element. The corner cube prism is insensitive to misalignment in any direction. We demonstrate experimentally that a laser cavity with such a prism provides stable laser performance under violent changes of ambient temperature and the effect of the laser crystal thermal lens. The laser mode properties are analyzed by numerical simulations. We show that the numerically simulated results agree well with the experimental ones.     

Q-switched and mode-locked diode-pumped Nd:YAG laser with an LT-GaAs

Simultaneous Q-switching and mode-locking (QML) is accomplished in a diode-pumped Nd:YAG laser using low-temperature GaAs (LT-GaAs) as the saturable absorber, which also acts as an output coupler at the same time. The repetition rate of the Q-switched envelope increased from 25 to 40 kHz as the pump power increased from 2.2 to 6.9 W. The mode-locked pulses inside the Q-switched pulse envelope had a repetition rate of 714 MHz. A maximum average output power of 770 mW was obtained.     

Pulsed Nd:YAG passive Q-switched laser using Cr4+:YAG crystal

In this paper, we report the experimental results of a pulsed flash lamp Nd:YAG laser at wavelength of 1064 nm and Q-switched by Cr⁴⁺:YAG solid state saturable absorber. We have obtained the output energy (E) and pulse- width (τ_p) of this laser for various initial transmissions of this saturable absorber. Furthermore, the effect of reflectivity of the output coupler (R), diameter of the rod (d), and optical length of the cavity (l) on this laser output data have been investigated. We have used the corner cube as a back mirror, which shows high laser stability and better brightness. We have obtained pulse-width 15 ns with 31 mJ output energy. We have also analyzed this laser theoretically and analytically, which agrees well with our corresponding experimental results.     

Diode pumped Nd:YAG laser repetitively Q-switched with Cr4+:YAG

Based on the rate equations of passively Q-switched solid state lasers, the performance of laser at a fixed pump power can be optimized through the proper choice of output coupler and the low-intensity transmission of saturable absorber. A simple expression for optimizing these two parameters is derived in this paper. We also demonstrate the performance of an efficient diode-pumpe Cr⁴⁺:YAG passively Q-switched Nd:YAG laser to generate a high-repetition-ate, high-peak power 1064 nm laser pulses, which providing pulses peak power > 10 kW with high repetition rate up to 150 kHz, and the pulse width as short as 6.8 ns.     

Thermal mode-switching of a passively Q-switched microchip Nd:YAG laser

In the present article, the thermal distribution inside the gain medium of a passively Q-switched microchip laser is modeled and simulated for actual practical values associated with an available microchip laser constructed in our laboratory. The effects of the non-uniform heat distribution on the spectral properties of the output laser beam have been investigated and simulated with the variation of diode-pump power and pulse repetition rate. It is observed that the gain bandwidth as well as Optical Path Difference (OPD) values of the propagating pulses are significantly decreased, while the Nd:YAG chip is cooled down to a certain value. The validity of the utilized model is checked by setting and characterizing the spectral properties of a fabricated laboratory microchip laser under different heating conditions. It is verified that when the temperature of the gain material is changed by an electronically controlled Peltier device, the spectrum of the output laser beam can be switched between single- and dual-mode situations. This physical character has shown good agreement between the presented model and obtained experimental results.     

Passively Q-switched Nd3+:YAG laser with corner cube

A passively Q-switched Nd3+:YAG laser with corner cube is theoretically and experimentally studied. We analyze the polarization variation in cavity and simulate the peak power, pulse energy and pulse width changed with the rotation angle of corner cube numerically. An experiment is made to verify the theoretical results. With rotating the angle of corner cube about the axis the variation range of peak power is 1.77 MW (from 10.36 to 8.59 MW), and that of pulse energy is 14.9 mJ (from 159.5 to 174.4 mJ), the fluctuation of pulse width is 2.95 ns. The experimental results agree with the theoretical analysis to the extent of variation rules. The most dynamic to static energy ratio of 62.5% is achieved.     

High-power Q-switched Nd:YAG laser mounted in a silicon microbench

A high-power Q-switched Nd:YAG/Cr:YAG laser mounted in a silicon microbench is presented. It reaches an average output power well above 2 W and the pulse width is in the order of 1.4 ns. The use of microstructure silicon carriers provides efficient thermal control, compact integration and alignment of active and passive optical components.     

High-efficiency diode-pumped acousto-optically Q-switched 1123 nm ceramic Nd:YAG laser

A high-efficiency diode-pumped acousto-optically (AO) Q-switched ceramic Nd:YAG (cNd:YAG) laser operating at 1123 nm is demonstrated for the first time. With an incident pump power of 17.11 W and a pulse repetition rate of 30 kHz, an average output power of 5.86 W is obtained. The optical-to-optical conversion efficiency is 34.2% and the slope efficiency is 39.1%.     

Wood engraving by Q-switched diode-pumped frequency-doubled Nd:YAG green laser

Laser deep engraving is one of the most promising technologies to be used in wood carver operations. In this method, a laser beam is used to ablate a solid wood bulk, following predetermined patterns. The sculpture is obtained by repeating this process on each successive thin layer. Obviously, in order to achieve larger material removal rates, the process needs a controllable variation of the depth to carve a 3D (three dimensional) profiles.The degree of precision of the shape, the removal rate and the surface quality during the engraving process strictly depend on the materials properties, the laser source characteristics and the process parameters.The aim of this work is to investigate the influence of the process parameters on the material removal rates by engraving panels made of different types of wood using a Q-switched diode-pumped Nd:YAG green laser working with a wavelength λ=532 nm. The examined parameters were: the mean power that depends on the pulse frequency, the beam speed and the number of laser scansions, also called repetitions. The working parameters and the engraved depth were related and an energy-based model was proposed in order to predict the latter.Experimental results showed that the Q-switched diode-pumped frequency-doubled Nd:YAG green laser can be successfully used to machine different types of wood, obtaining decorative drawing and 3D engraved geometries without burning. However, an accurate selection of the wood types and the process parameters is necessary in order to obtain deep engraving without carbonization and a homogeneous carving.     

Radially polarized,actively Q-switched,and end-pumped Nd:YAG laser

In this paper, we demonstrated an actively Q-switched, radially polarized, and laser-diode end-pumped Nd:YAG laser with an acousto-optic modulator as the Q switch and a photonic crystal grating as the output coupler. The laser generated pulses of 26.4–67.2 ns duration, and the repetition rate can be continuously adjusted from 500 Hz to 9.238 kHz with peak power up to 7.75 kW. Such a radially polarized pulse would facilitate numerous applications.     

LBO intracavity frequency doubled, Cr:YAG passively Q-switched Nd:YAG green laser

A LD-pumped, LBO intracavity frequency doubled and Cr:YAG passively Q-switched Nd:YAG green laser was reported in this letter. With 600 mW incident pump laser, Q-switched green laser with average power of 27 mW, pulse width of 15.2 ns, repetition rate of 16.4 kHz and peak power of 108.1 W was obtained.     

High performance Cr4+:YAG Q-switched CW diode pumped Nd:YAG laser

This paper reports the operation of a Cr4+:YAG Q-switched CW diode laser pumped Nd:YAG at 1064nm. The laser performances resulted in 167 μ J, 21ns pulses at 10kHz, and 1.67W power output. When intracavity polarized, stable amplitude (fluctuations <±1%), TEM00, 153 μ J pulses were generated allowing 50% SHG in KTP. This revised version was published online in November 2006 with corrections to the Cover Date.