基于LD双端面泵浦的Nd:YAG高效率倍频激光器

报道了一种利用激光二极管（LD）双端面泵浦的Nd：YAG激光晶体,Cr⁴⁺：YAG晶体被动调Q,LBO临界相位匹配腔内倍频的高转换效率的绿光激光器。分析了双端面泵浦YAG激光器的热效应,实验中LD双端面泵浦,采用U型平行平面腔结构对Nd：YAG进行传导冷却。当总泵浦光为33.8 W时,得到被动调Q频率10 KHz、功率8.21 W的线偏振基频光输出。6.72 W的绿光输出的倍频效率为86%,输出光束为基模,M²为1.4。实验表明双端面泵浦YAG倍频激光器具有很高的转换效率。     

A linearly polarized continuous-wave 1357-nm Nd:YAG laser

We demonstrated a linearly polarized continuous-wave Nd:YAG laser operating at a 1357-nm single-wavelength, by a 808-nm diode as an end-pump source. We chose a Brewster-angle-cut Nd:YAG laser host crystal, due to its two salient features as follow: linearly polarized laser output and single-wavelength oscillation can be easily obtained. In this paper, a continuous-wave all-solid-state single-wavelength laser operating at 1357 nm is demonstrated with a diode-end-pumped Brewster-cut Nd:YAG laser. The laser had a 1.03-W maximum output power under an incident pump power of 15.0 W, a 12.7% slope efficiency, a 6.9% optical-to-optical conversion efficiency, a 0.14-nm spectral linewidth and a 3% power-output stability within 30 min. PACS 42.55.Rz; 42.55.Xi; 42.70.Hj     

High repetition rate,high peak power acousto-optical Q-switched 946 nm Nd:YAG laser

A diode-end-pumped high repetition rate, high peak power acousto-optical (AO) Q-switched 946 nm Nd:YAG laser was demonstrated in this paper. In our experiments, a 20 mm miniature acousto-optical Q-switch was employed in a 45 mm linear laser cavity for generating the short laser pulse. At a repetition rate of 10 kHz, a maximum average output power of 2.9 W was achieved with a pulse width of 24.4 ns, giving a peak power of 11.9 kW. To the best of our knowledge, this is the highest peak power 946 nm Nd:YAG laser at high repetition rate operation. Moreover, pulse train with good stability was also obtained at the repetition rate of 50 kHz. At an incident pump power of 22.3 W, up to an average output power of 3.5 W pulsed 946 nm laser was generated at 50 kHz with a pulse width of 69 ns, corresponding to an optical conversion efficiency of 15.7% and an average slope efficiency of 24.1%, respectively.     

Properties of continuous-wave 1123 nm laser with diode-side-pumped Nd:YAG

Laser properties of diode-side-pumped Nd:YAG laser operating at 1123 nm are demonstrated. A 1.0 at % Nd-doped Nd:YAG rod with a size of Ø3 × 63 mm² is used as the active medium. Both radial and tangential thermal focal lengths of this side-pumped Nd:YAG rod are determined under lasing condition. The results show that the bifocusing strength of 1123 nm laser is larger than that of 1164 nm laser, and 1123-nm thermal focal lengths are shorter than those of 1064-nm laser due to higher quantum defect. Laser output performances of 1123 nm in terms of stability, output power and beam quality influenced by pump power at different cavity lengths are also discussed with a convex-piano cavity.     

LD端面泵浦Cr~4∶YAG被动调Q激光器输出特性研究

对激光二极管端面泵浦Cr4+∶YAG被动调Q Nd∶YAG激光器输出特性进行了实验研究.实验研究发现,激光器输出功率及脉冲重复频率随谐振腔长度增大而增大.为解释这一实验现象,测量了泵浦光斑在激光晶体内尺寸,同时计算了激光晶体及Cr4+∶YAG晶体内的基模激光光斑半径随谐振腔长度变化.分析结果表明:激光晶体内泵浦光斑尺寸远小于激光晶体内基模光斑半径,腔模间交叠效率较低;当腔长增加时,激光晶体内的基模激光光斑减小,腔模间交叠效率增加,从而导致输出功率及脉冲重复频率随腔长增加而增加;另外,Cr4+∶YAG晶体内光斑半径也随谐振腔长度减小,引起Cr4+∶YAG晶体漂白时间缩短,导致脉冲重复频率随腔长增加而增加.     

LD端面泵浦Cr4:YAG被动调Q激光器输出特性研究

对激光二极管端面泵浦Cr⁴⁺:YAG被动调QNd:YAG激光器输出特性进行了实验研究.实验研究发现,激光器输出功率及脉冲重复频率随谐振腔长度增大而增大.为解释这一实验现象,测量了泵浦光斑在激光晶体内尺寸,同时计算了激光晶体及Cr⁴⁺:YAG晶体内的基模激光光斑半径随谐振腔长度变化.分析结果表明:激光晶体内泵浦光斑尺寸远小于激光晶体内基模光斑半径,腔模间交叠效率较低;当腔长增加时,激光晶体内的基模激光光斑减小,腔模间交叠效率增加,从而导致输出功率及脉冲重复频率随腔长增加而增加;另外,Cr⁴⁺:YAG晶体内光斑半径也随谐振腔长度减小,引起Cr⁴⁺:YAG晶体漂白时间缩短,导致脉冲重复频率随腔长增加而增加.     

Radially polarized laser beam from a Nd:YAG laser cavity with a c-cut YVO4 crystal

We demonstrate the generation of a radially polarized beam by simply inserting an undoped c-cut YVO₄ crystal into a Nd:YAG laser cavity. In a hemispherical cavity, the cylindrically symmetric, positive birefringence of the YVO₄ crystal extends the stability limit of the cavity length for an extraordinary ray (radial polarization) compared to an ordinary one (azimuthal polarization). By adjusting the cavity length, a radially polarized beam with an output power up to 1 W was selectively obtained. In addition, a higher-order transverse mode was also generated by arranging the cavity design. The method demonstrated in this paper can be readily applied to laser systems with an isotropic laser medium. PACS 42.60.Da; 42.25.Lc; 42.25.Ja     

Production of radially or azimuthally polarized beams in solid-state lasers and the elimination of thermally induced birefringence effects

Production and amplification of radially and azimuthally (tangentially) polarized laser beams are demonstrated. Based on the different focusing between radially and tangentially polarized light in thermally stressed isotropic laser rods, Nd:YAG laser oscillators were developed to produce low-loss stable oscillation in a single polarization. Pure radially polarized light at 70 W with M2 = 2 and on-axis impure radially polarized light at 150 W with M2 = 2.5 were achieved. The radially polarized beams were then amplified while good beam quality and polarization purity were retained. Complete elimination of thermal-birefringence-induced aberrations was demonstrated. This should allow much better beam quality from rod-based high-power lasers.     

High energy and high stability Cr:YAG passively Q-switched laser with convex-ARR unstable resonator

A convex-ARR (Anti-resonant Ring) unstable resonator was introduced in a Cr⁴⁺:YAG passively Q-switched Nd:YAG pulsed laser. There are two novel features in this cavity, one is the unstable resonator increasing output energy and improving laser mode; the other is the ARR structure efficiently enhancing the laser stability. A high energy and high stability Q-switched pulse with a single pulse energy of 85.6 mJ, a pulse width of 38 ns and an energy stability of 99.6% was obtained. The experimental results were analyzed well by using the mechanism of transient grating and the properties of the unstable resonator.     

A high-power high-stability Q-switched green laser with intracavity frequency doubling using a diode-pumped composite ceramic Nd：YAG laser

We successfully obtain a high-average-power high-stability Q-switched green laser based on diode-side-pumped composite ceramic Nd:YAG in a straight plano-concave cavity. The temperature distribution in composite ceramic Nd:YAG crystal is numerically analyzed and compared with that of conventional Nd:YAG crystal. By using a composite ceramic Nd:YAG rod and a type-II high gray track resistance KTP (HGTR-KTP) crystal, a green laser with an average output power of 165 W is obtained at a repetition rate of 25 kHz, with a diode-to-green optical conversion of 14.68%, and a pulse width of 162 ns. To the best of our knowledge, both the output power and optical-to-optical efficiency are the highest values for green laser systems with intracavity frequency doubling of this novel composite ceramic Nd:YAG laser to date. The power fluctuation at around 160 W is lower than 0.3% in 2.5 hours.     

High-power high-stability Q-switched green laser with intracavity frequency doubling of diode-pumped composite ceramic Nd:YAG laser

We successfully obtain high-average-power high-stability Q-switched green laser based on diode-side-pumped composite ceramic Nd:YAG in a straight plano-concave cavity. The temperature distribution in composite ceramic Nd:YAG crystal is numerically analyzed and compared with that of conventional Nd:YAG crystal. By use of a composite ceramic Nd:YAG rod and a type-II high gray track resistance KTP (HGTR-KTP) crystal, a green laser with an average output power of 165 W is obtained at a repetition rate of 25 kHz, with a diode-to-green optical conversion of 14.68%, and a pulse width of 162 ns. To the best of our knowledge, both the output power and optical-to-optical efficiency are the highest values for green laser systems with intracavity frequency doubling of this novel composite ceramic Nd:YAG laser to date. The power fluctuation at around 160 W is lower than 0.3% in 2.5 hours.     

腔内偏振元件对激光特性的影响

Nd:YAG固体激光器的偏振特性在许多实际应用中非常重要.特别是在非线性光学频率变换中,无论是实现Ⅰ类相位匹配还是Ⅱ类相位匹配的非线性光学晶体,对基频光的偏振特性都有一定的要求.研究了半导体激光侧向泵浦固体Nd:YAG激光器的偏振特性.实验测量了腔内镀膜偏振片和它们在腔内不同位置时对激光偏振特性的影响.消光比测量表明,...     

Simple Nd:YAG laser generates vector and vortex beam

We report a simple Nd:YAG laser that emits radially polarized beam with helical wavefront. The laser cavity consists of a piece of laser crystal and a plane output coupler, and there is no additional polarization component inside it. The pump light is converted into annular profile through de-focal coupling into a multi-mode fiber. For the continuous-wave(CW) operation, the laser emits radially polarized vortex beam, and it is observed that the helical wavefront of the laser beam is switched from right handedness to left handedness when the output coupler is tilted slightly. For the Q-switched operation under the insertion of a Cr4t:YAG saturable absorber inside the cavity, we obtain radially polarized outputs with left-handedness helical wavefront. By tilting the laser crystal slightly, the laser output switches to azimuthal polarization at pump power larger than 4.5 W and left-handedness helical wavefront of laser beam is preserved.     

高稳定性低噪声的561 nm黄光激光器

鉴于目前561 nm激光器噪声较大,影响其实用性,提出一种高稳定性低噪声的561 nm黄光激光器。利用Nd:YAG晶体得到1 123 nm基频光,通过LBO晶体腔内倍频得到561 nm输出。理论分析了1 112 nm、1 116 nm与1 123 nm波长的阈值泵浦功率,提出1 123 nm的单波长振荡条件,确定谐振腔镀膜要求。根据理论计算,设计了合理的谐振腔膜系,通过抑制1 112 nm与1 116 nm谱线在谐振腔内的振荡实现1 123 nm谱线的单波长振荡。在泵浦功率为5 W时,实现了561 nm激光单波长输出,输出功率达到107 mW,功率不稳定性达到0.7%,噪声为1.2%。     

高功率准连续波腔内和频全固态黄光激光器

报道了高功率准连续波腔内和频全固态黄光激光器的研究结果.为获得高功率的黄光输出,首先,激光器采用准连续方式运转,在保持抽运水平的条件下降低热效应,从而提高光束质量和光光转换效率;第二,采用热近非稳腔腔型设计,双棒串接补偿热致双折射技术,获得大基模体积高光束质量的基频光;第三,通过优化腔型,采用L型共折叠臂平-凹对称腔,使两束基频光达到空间重合且满足功率配比.通过这些方法,得到了输出功率7.6W,重复频率1.1kHz的准连续波黄光输出.据我们所知,这是目前腔内和频方案所获得的最高功率全固态黄光输出. 关键词： 黄光激光 腔内和频 Nd：YAG激光 全固态激光器     

高功率腔内双共振2μm光参量振荡器特性研究

报道了一种稳定的高功率双共振2?μm 光参量振荡器（OPO）. 该OPO使用调Q的线偏振全固态Nd∶YAG激光器作为抽运源,利用双棒串接补偿热致双折射和双Q开关正交放置技术提高了抽运源的输出功率和光束质量,通过腔内抽运单块KTP晶体实现了稳定的高功率2?μm 激光输出. 在调Q频率为5?kHz时,得到了295 W的2?μm 激光输出. 研究了OPO输出功率同KTP晶体温度和声光Q调制频率的关系,并测量了在29W时2?μm激光的功率稳定性. 在1 h内该OPO的功率起伏小于1.4%. 关键词： 光参量振荡器 2?μm激光器 KTP晶体 双共振     

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.     

High power and highly efficient Nd:YAG laser emitting at 1123 nm

A diode-end-pumped continuous-wave (CW) Nd:YAG laser emitting at 1123 nm is realized efficiently in a 25-mm-long cavity. A composite Nd:YAG (cNd:YAG) crystal is selected as the gain medium. With an incident diode power of 26.1 W, an output power of up to 9.3 W is obtained, corresponding to an optical-to-optical conversion efficiency of 35.6%. The laser performances at 1123 nm are compared between composite Nd:YAG and common Nd:YAG crystals. The results show that composite Nd:YAG is a better choice for 1123-nm laser generations.     

High-power continuous wave green beam generation by use of simple linear cavity with side-pumped module

High-power continuous wave green radiation has been generated by means of type-II phase-matched frequency doubling in a KTP crystal located in a simple linear cavity incorporating a diode side-pumped Nd:YAG laser module. The cavity was designed to make the fundamental beam radius at the KTP crystal smaller than that at the gain medium, as is required for obtaining large mode volume in Nd:YAG crystal and realizing efficient CW intracavity frequency doubling. Output power of 51.2 W is obtained in the experiment with a diode-to-green optical conversion efficiency of 10.3%. The M²-parameters of the laser are measured at different output powers. For the output power of about 47 W, the power fluctuation is measured less than 1%. The experimental results show that the continuous wave green laser system using this simple linear cavity offers good laser performance and output stability.     

LD侧泵Nd∶YAG/S-KTP腔内倍频高功率660nm连续红光激光器

报道了LD侧面泵浦Nd∶YAG/S-KTP腔内倍频高功率660nm连续红光激光器。泵浦组件（呈三角形等间距分布）由9个20W的激光二极管组成，最大泵浦功率为180W。通过对谐振腔参数进行优化设计，用LD连续抽运3mm×65mm Nd∶YAG激光棒时，获得了波长为1319nm的基频光振荡。利用S-KTP II类临界相位匹配腔内倍频技术，当泵浦电流为22A时，获得了6.8W的连续红光激光输出，光-光转换效率为4.3％。