Laser-diode-pumped Nd:YVO<Subscript>4</Subscript>/Nd:YAG MOPA burst-mode laser

We report a high-repetition-rate, high-peak-power laser diode (LD) pumped burst-mode 1064 nm laser from a Nd:YVO₄/Nd:YAG master oscillator power amplifier. 10–100 kHz pulse burst in a duration up to 2 ms is achieved in LD end-pumped Nd:YVO₄ acousto-optically Q-switched laser. After amplification with LD side-pumped Nd:YAG rod amplifiers, the single pulse energy reaches 73 mJ in 10 kHz pulse burst laser with a peak power of 7.8 MW.     

A compact subnanosecond high power Nd:YAG laser system

In this paper, a high power Nd:YAG laser system is described, which consists of an actively-passively mode-locked Nd:YAG laser oscillator with variable subnanosecond pulsewidths (200 ps to 1 ns), a Pockels-cell shutter and a coaxial four-pass Nd:YAG amplifier. With the oscillator operating in the colliding pulse regime, and a BDN dye film as the saturable absorber, and an acousto-optic modulator as the active modelocker, we have achieved a shot-to-shot stability of the pulse-train amplitude < ±4%. For a 0.1 mJ, 200 ps laser pulse, we obtained four-pass amplification of 7 × 10² with a pump energy of 106 J.     

A kilowatt level diode-side-pumped QCW Nd:YAG ceramic laser

We demonstrate a kilowatt level Quasi-continuous-wave (QCW) diode-side-pumped Nd:YAG ceramic laser at 1064 nm. The laser system adopts a master oscillator power amplifier scheme (MOPA). The master oscillator contains two diode-pumped laser modules. Under the pump power of 2000 W, an output power of 686 W was obtained. After amplified by an identical ceramic laser module, a maximum output power of 1020 W was obtained under a total incident pump power of 3433 W, corresponding to an optical-optical conversion efficiency of 29.7%. At the maximal output power, the repetition frequency was measured to be 1 kHz and the pulse width was 114 μs. To the best of our knowledge, this is the first time to realize QCW side-pumped Nd:YAG ceramic laser system with output power above 1 kW.     

8-mJ TEM(00) diode-end-pumped frequency-quadrupled Nd:YAG laser

A frequency-quadrupled Nd:YAG laser pumped by a commercially available high-brightness stack is described. A master oscillator power amplifier configuration was implanted, and the laser delivered energy of 8 mJ at 0.266microm . The laser was air cooled for easy use.     

High power high beam quality diode-pumped 1319-nm Nd:YAG oscillator-amplifier laser system

This paper demonstrated a high power and high beam quality diode-pumped 1319-nm Nd:YAG master oscillator-power amplifier laser system. A thermally near-unstable resonator with four-rod birefringence compensation flat--flat cavity was adopted as the master oscillator. A solid etalon was inserted in the unidirectional ring resonator to compress the laser linewidth. Under a repetition rate of 500~Hz and pulse width of 160~\mus, the master oscillator delivers an average output power of 16.8~W at 1319~nm with linear polarisation, beam quality factor M^{2} = 1.16 and linewidth of 3.2~GHz. A double-pass power amplifier with two amplifier stages was employed for higher power scaling and the output power was amplified to be 25.9~W with M^{2} = 1.43.     

Studies on Nd:YAG Single-pass Amplifiers for High-power Q-switched Laser System

The output of Nd∶YAG single-pass laser amplifiers is studied analytically and experimentally. Methods of analysis for single-pass Nd∶YAG laser amplifier are presented. A flashlamp-pumped Q-switched Nd∶YAG oscillator/amplifier laser system has been developed with the average output power of 121.5 W.     

High power composite Nd:YAG/YAG zigzag dual-slab laser oscillator

We report a high power zigzag slab laser oscillator employing two composite Nd:YAG/YAG slab in the cavity. The CW laser output with the power of 401 W was achieved from the oscillator with the optical-optical efficiency of 32.6%. The beam quality is estimated as M _x ² ≈ 10, M _y ² ∼ 50 in the slab width and thickness direction, respectively.     

激光二极管抽运的高重频高平均功率Nd:YAG激光器

搭建了一台高重复频率、高峰值功率、高平均功率的激光器. 激光器主要包括三部分: 单纵模光纤种子源、激光二极管阵列抽运的Nd:YAG再生放大器和四程放大器. 系统获得了平均功率11 W、重复频率100 Hz、脉冲能量112 mJ、脉宽500 ps–2 ns可调的激光输出, 工作波长1064 nm. 输出光束口径6.8 mm, 1.5倍衍射极限, 近场光强近平顶分布, 能量稳定性为0.72%. 关键词： 激光二极管抽运 高重复频率 高峰值功率 高平均功率     

脉宽易变的高功率Nd:YAG激光器

本文描述一台由两级Nd:YAG激光器组成的紧凑高功率激光系统的结构及其工作性能。激光系统分成三个部分:对撞脉冲式的主-被动锁模振荡器,单脉冲选择器和四程放大器。振荡器输出锁模脉冲列的包络幅度起伏小于±4％,其脉冲宽度可以在宽范围内(20ps～2.5ns)方便地切换。对于单个0.1mJ、200ps的激光脉冲,四程放大器能提供7×10~2的放大倍数。     

Studies on Nd∶YAG Single-pass Amplifiers for High-power Q-switched Laser System

The output of Nd∶YAG single-pass laser amplifiers is studied analytically and experimentally. Methods of analysis for single-pass Nd∶YAG laser amplifier are presented. A flashlamp-pumped Q-switched Nd∶YAG oscillator/amplifier laser system has been developed with the average output power of 121.5 W.     

Temperature characteristics of small signal gain for Nd/Cr:YAG ceramic lasers

Thermal dependence on the small signal gain of Nd/Cr:YAG (yttrium aluminum garnet) ceramics was observed experimentally. Usually, Nd:YAG crystal and ceramics have remarkable gain reduction when optical pumping is performed and the temperature of the laser media is upped to 373 K. A CW laser light generated in a 1064 nm Nd:YAG laser oscillator was amplified by Nd/Cr:YAG ceramic amplifier, and the output power was measured at non-saturation level. Laser small signal gain of the ceramic disk was kept to 470 K. This property was remarkably different from one of Nd:YAG crystals or ceramics. The peak shift of the fluorescence was observed experimentally when the temperature is high.     

Passively Q-switched mode-locking in a diode-pumped Nd:LuVO<Subscript>4</Subscript> laser with V:YAG

A passively Q-switched and mode-locked Nd:LuVO₄ laser with V:YAG at 1.34 μm was successfully demonstrated. Comparisons between c-cut and a-cut Nd:LuVO₄ lasers were experimentally made. The maximum average output power of 170 mW, the highest Q-switched pulse energy of 4.5 μJ were obtained in c-cut Nd:LuVO₄ laser. The duration of mode-locked pulse was estimated to be less than 540 ps with repetition rate of 110 MHz.     

Fabrication and laser performance of highly transparent Nd:YAG ceramics from well-dispersed Nd:Y<Subscript>2</Subscript>O<Subscript>3</Subscript> nanopowders by freeze-drying

Well-dispersed Nd:Y₂O₃ powders with uniform particle size of about 60 nm were synthesized from freeze-dried precursors. Highly transparent 2 at.% Nd:YAG ceramics were fabricated from the as-synthesized Nd:Y₂O₃ powders and commercial Al₂O₃ powders by vacuum sintering at 1,750 °C for 5 h. Phase evolution, microstructures, and spectroscopic properties of the Nd:YAG transparent ceramics were investigated. Freeze-drying played an important role in the synthesis of high-quality Nd:Y₂O₃ nanosized powders, which were essential for the fabrication of highly transparent Nd:YAG ceramics. Optical transmittance of a 3-mm thick sample reached 82% in the wavelength range of 200–900 nm. 5.23 W output power was obtained with 14.3 W diode laser pumping, giving a slope efficiency of 36.5%.     

Frequency jitter and spectral width of an injection-seeded Q-switched Nd:YAG laser for a Doppler wind lidar

The design of a 50 Hz single longitudinal mode, diode-pumped and frequency-tripled Nd:YAG master oscillator power amplifier is described, and the first measurements of output parameters are presented. The laser oscillator is injection-seeded by a tuneable monolithic Nd:YAG ring laser and frequency stabilized by minimising the Q-switch build-up time. The laser system will be an integral part of an airborne instrument demonstrator for a first satellite based Doppler wind lidar to measure vertical profiles of one component of the atmospheric wind vector. This paper focuses on the investigation of the frequency jitter and the linewidth of the laser, which are measured on a pulse-to-pulse basis. For this purpose a compact, high accuracy beat frequency monitoring system has been developed at DLR. By operating the amplifier stage at half the repetition rate (50 Hz) of the oscillator, we could reduce the frequency stability from 10 MHz (rms) to 1.3 MHz (rms) (over a 14 s period). We have determined a mean linewidth of 15 MHz (FWHM) at 1064 nm. These measured laser parameters enable wind velocity measurements in the atmosphere (0–15 km) at an accuracy of 1 to 2 m/s. PACS 42.55.Xi; 42.60.Lh; 42.68.Wt     

Continuous-wave intracavity frequency-doubled Nd:Yag-KTiOPO<Subscript>4</Subscript> red laser

Efficient and compact red laser output at 669 nm is generated by intracavity frequency doubling of a continuous-wave (CW) diode-pumped Nd:YAG laser at 1338 nm. With 16.9 W of diode pump power and the frequency-doubling crystal KTiOPO₄ (KTP), a maximum output power of 582 mW in the red spectral range at 669 nm has been achieved, corresponding to an optical-to-optical conversion efficiency of 3.4%; the output power stability over 4 h is better than 3.6%. To the best of our knowledge, this is first work on intracavity frequency doubling of a diode pumped Nd:YAG laser at 669 nm.     

Nd:YAG laser/KTiOAsO4 (KTA) OPO system for laser ultrasound measurements on carbon-fiber-reinforced composite materials

We report on a 3.3 μm laser/optical parametric oscillator system with 4.7 mJ pulse energy for laser ultrasound measurements of carbon-fiber-reinforced materials. The OPO was pumped by a compact diode-pumped Nd:YAG master-oscillator power-amplifier system with two amplifier stages. First results of laser ultrasound measurements are presented.     

Rotating-disk diode-pumped continuous-wave Nd:YAG laser

Continuous-Wave (CW) diode-laser-pumped experiments using rotating Nd: YAG disk(s) have been performed in the input-power range of 1–6 W and rotation-speed range of 0–25 Hz. With a single Nd: YAG disk in the laser cavity, about 1.56 W of output power at 1.06 µm due to the Nd³⁺ (⁴ F _3/2–⁴ I _11/2) transition at an absorbed input power of 4.2 W has been observed, leading to an optical-to-optical conversion efficiency of over 37% and slope efficiency of 52% using 7.5% transmission output coupler. The laser output power has been observed to decrease by either increasing the number of Nd:YAG disks in the cavity or increasing the rotation speed of the disk(s).     

400-Hz pulsed single-longitudinal-mode Nd:YAG laser with more than 100-mJ pulse energy and good beam quality

An all solid state master-oscillator-power-amplifier laser system was experimentally investigated using a pulsed-diode-pumped single-longitudinal-mode Nd:YAG laser as a master oscillator. The system was operated with 400 Hz pulse repetition rate. The amplifiers contain a pre-amplifier and a power amplifier. A specially designed large aperture tapered fiber as a solid state phase conjugation mirror was used in the power amplifier to improve the beam quality. The maximum pulse energy of 101 mJ is obtained after double-pass amplification. The pulse duration is less than 6 ns. The corresponding peak power reached 16.8 MW for each single pulse.     

Timing-jitter reduced high-repetition-rate Q-switched Nd:YVO<Subscript>4</Subscript>/Cr<Superscript>4+</Superscript>:YAG micro laser with low pump power

We report a high repetition rate Q-switched Nd:YVO₄/Cr⁴⁺:YAG micro laser with small pump power. Unwanted defects in pulse train, which are inherently large in passively Q-switched laser, was simply minimized by controlling temperature of Nd:YVO₄/Cr⁴⁺:YAG medium. When T ₀ = 90% Cr⁴⁺:YAG and R _OC = 90% output coupler were used, Q-switched Nd:YVO₄/Cr⁴⁺:YAG micro laser showed the optimum output; maximum output power of 58 mW, optical-to-optical efficiency of 9.1%, repetition rate of 1.1 MHz, and pulse width of 57 ns were achieved with 640 mW pumping. MHz-order repetition rate in Nd:YVO₄/Cr⁴⁺:YAG Q-switched laser with low pumping (<1 W) is the highest value to the best of our knowledge.     

Intracavity optical parametric oscillator pumped by an actively Q-switched Nd:YAG laser

A non-critically phase-matched KTiOPO₄ optical parametric oscillator (OPO) intracavity pumped by a laser diode end-pumped acousto-optically Q-switchedNd:YAG laser is experimentally demonstrated. The highest average power is obtained at the pulse repetition rate (PRR) of around 15 kHz, which is different from the widely reported Nd:YVO₄ laser pumped OPO in which the highest average power is obtained at a very high PRR, e.g. 80 kHz. With an incident laser diode power of 6.93 W and a pulse repetition rate of 15 kHz, an average signal power of 0.72 W is obtained with a peak power of 7.7 kW and an optical-to-optical conversion efficiency of 10.4%. PACS 42.65.Yj; 42.60.Gd; 42.55.Xi