Harmonic and sum-frequency generation of pulsed laser radiation in BBO,LBO, and KD*P

The optical properties of the nonlinear crystals lithium borate (LBO), barium borate (BBO) and deuterated potassium phosphate (KD*P) are compared for second and third harmonic generation of Nd:YAG laser radiation. In an experimental investigation the conversion efficiency has been measured as a function of the energy density of 8 ns long laser pulses, generated by a commercial Nd:YAG oscillator-amplifier system. In LBO and BBO the second harmonic generation saturates at an energy density of about 1.5 J cm^–2 at efficiencies of 55–60%. In KD*P comparable efficiencies (40–55%) require energy densities of 2–2.6 J cm^–2. Similar results are obtained for frequency tripling. In LBO and BBO saturated efficiencies of 20–25% are measured at an energy density of about 1.5 J cm^–2. In KD*P efficiencies of 20% are obtained at energy densities exceeding 2 J cm^–2. Besides for doubling and tripling of Nd:YAG laser radiation the phase-matching is calculated for frequency conversion of tunable laser light. The results demonstrate that in LBO and BBO phase-matched sum-frequency mixing of UV and infrared laser light generates tunable radiation at wavelengths as short as the transmission cut-off at 160 nm and 190 nm, respectively.     

High power continues wave laser diode array end pumped Nd:YAG/LBO red lasers operated at 669 nm and 659 nm

In this paper, we present using Nd:YAG as the laser media, and Brewster plate as a polarizer device to obtain the linear polarization output at the fundamental wavelength. Using LBO (LiB₃O₅) crystal as non-linear crystal to obtain intra-cavity frequency doubled red laser at 659 and 669 nm and sum frequency mixing at 665 nm. Using a thin fused silica plate as an etalon to obtain the single wavelength operation. At total pump power of 30 W at 808 nm, the output powers at two wavelengths are about 4.1 and 4.5 W, respectively, only one fundamental wavelength light is resonating. The corresponding optical to optical conversion efficiency from pump light to second harmonic generation are 13.7 and 15.0%, respectively.     

2.41 W compact efficient CW blue light generation by intra-cavity frequency doubling of a compact Nd:YAG laser

We report on a laser diode end-pumped Nd:YAG blue laser using a three-mirror-folded cavity. Three different crystals cut for type-I critical phase matching are used for the intra-cavity frequency doubling of the laser: 10-mm-long LiB₃O₅ (LBO), 15-mm-long LBO, and 10-mm-long BiB₃O₆ (BIBO). Up to 2.41 W of continuous wave output power in the blue spectral range at 473 nm is achieved with BIBO crystal (1.89 W with LBO) at the incident pump power of 16 W, the light-to-light conversion efficiency is about 15.1%.     

双轴晶体LiB3O5和频与倍频转换特性的研究

本文在光学主轴坐标系下,对双轴晶体LiB3O5共线和频与倍频特性进行了计算与分析.给出了xy面应用tyyeⅠ相位匹配及yz面应用typeⅡ相位匹配情况下,基波波长与相位匹配角、有效非线性系数、离散角、容承角及基波频谱带宽的关系曲线,对LiB3O5晶体的实验与应用提供了有指导意义的理论结果.     

低对称性非线性光学晶体BIBO的倍频性质

测量了BIBO晶体的主轴折射率.对BIBO晶体在整个空间内的倍频性质进行了系统讨论.当基频 光为Nd:YAG激光时（λ=1064nm），发现最大的有效非线性光学系数位于（168.9°，90°） 的Ⅰ类相位匹配方向上.测量了BIBO晶体的容限角、容限温度、光损伤阈值，以及1064nm的 腔外、腔内倍频性质.实验中，最大腔外倍频转换效率达到68%，腔内倍频输出达到1.06W. 关键词： 低对称性 BIBO晶体 倍频     

高功率钕玻璃激光三倍频脉冲时间波形的研究

基于目前国内规模最大的激光驱动器——“神光Ⅱ”八路基频光已经实现功率平衡运行，通过改变其中若干路三倍频系统各调谐量的偏离，对输出三倍频波形进行束与束之间的横向对比研究.研究发现，对于Ⅱ类-Ⅱ类偏振失配三倍频系统，在影响转换效率的三个调谐量中，偏振分配角失配Δθ_p对三倍频波形影响最大；在入射基频功率密度约为1.0GW/cm²情况下，当三倍频系统三个调谐量都处在最佳匹配时，三倍频波形半峰全宽τ最小.研究工作为最终实现“神光Ⅱ”八路光束三倍频功率平衡输出提供了晶体调试 关键词： 三倍频 时间波形 功率平衡     

Tunable picosecond UV source at 10 kHz based on an all-solid-state diode-pumped laser system

4 laser. The amplified pulses were frequency-converted in the blue and in the UV by harmonic generation (doubling and tripling) in two lithium triborate (LBO) crystals. Received: 11 March 1997/Accepted: 24 April 1997     

Compact efficient diode-end-pumped intracavity frequency-tripled Nd:YVO<Subscript>4</Subscript> 355 nm laser

A compact efficient diode-end-pumped acousto-optically Q-switched intracavity-frequency-tripled Nd:YVO₄ 355 μm ultraviolet laser was realized. Intracavity sub-resonators with anti-reflection and high-reflection coated mirrors were used to get higher efficiency of third harmonic generation. With two LBO crystals used in frequency doubling and tripling processes, greater than 1.46 W 355 nm average output power was obtained under the absorbed pump power of 13.9 W and the repetition rate of 10 kHz. The corresponding pump-to-ultraviolet conversion efficiency was determined to be as high as 10.5%. At 10 kHz, the minimize pulse width was obtained to be 12 ns with the peak power of 10.4 kW and single pulse energy of 146 μJ.     

All-solid-state CW intracavity frequency-doubling Nd:Lu<Subscript>2</Subscript>O<Subscript>3</Subscript>/LBO red laser at 679.5 nm

We report an efficient intracavity second-harmonic generation (SHG) at 1359 nm in a non-linear optical crystal, LiB₃O₅ (LBO), performed with a diode end pumped continuous-wave (cw) Nd:Lu₂O₃ laser. In the case of a laser with a Nd:Lu₂O₃ crystal frequency-doubled with a LBO crystal cut for type I frequency doubling. A cw SHG output power of 462 mW has been obtained using a 10 mm long LBO crystal. The red power stability was 3.4% in 4 h.     

Diode-pumped 671 nm laser frequency doubled by CPM LBO

A design of diode-pumped high-efficiency Nd:YVO₄/LBO red laser is reported. Using critical phase-matching (CPM) LBO, 671 nm red laser was obtained from 1342 nm light by intracavity frequency doubling. With an incident pump laser of 800 mW, using type-I and type-II CPM LBO, 97 and 52 mWTEM₀₀ mode red laser outputs were obtained, with optical-to-optical conversion efficiencies of up to 12.1% and 6.5%, respectively.     

Non-linear crystals for tunable coherent sources

High-efficiency non-linear crystals suitable for the generation of coherent sources ranging from the deep ultraviolet to mid-infrared (0.16 to 5 µm) are explored. The key parameters for frequency conversion techniques (second-harmonic-generation, sumfrequency mixing, difference-frequency mixing, optical parametric oscillation (OPO) and stimulated Raman scattering) including tunability, beam quality, beam walk-off and the effective figure-of-merit are analysed. Materials selection rules for non-linear crystals (for wide transparency, high damage threshold, stability, low absorption and large figure-of-merit) are presented. Techniques using non-critical phase-matching, quasi-phase-matching, waveguided doubling and self-frequency doubling are explored. Features and applications of the new non-linear crystals ofβ-barium borate, lithium triborate (LBO), potassium titanyl phosphate (KTP), KNbO₃ and MgO:LiNbO₃ are presented and compared with other crystals. In addition to a critical review, this paper also presents some new results for the analysis of frequency-conversion efficiency, experimental data of OPO in KTP, LBO for frequency conversion using temperature-tuned non-critical phase-matching and green lasers from the diode-pumped self-frequency-doubling crystal of neodymium yttrium aluminium borate.

     

Non-linear crystals for tunable coherent sources

High-efficiency non-linear crystals suitable for the generation of coherent sources ranging from the deep ultraviolet to mid-infrared (0.16 to 5 µm) are explored. The key parameters for frequency conversion techniques (second-harmonic-generation, sumfrequency mixing, difference-frequency mixing, optical parametric oscillation (OPO) and stimulated Raman scattering) including tunability, beam quality, beam walk-off and the effective figure-of-merit are analysed. Materials selection rules for non-linear crystals (for wide transparency, high damage threshold, stability, low absorption and large figure-of-merit) are presented. Techniques using non-critical phase-matching, quasi-phase-matching, waveguided doubling and self-frequency doubling are explored. Features and applications of the new non-linear crystals of-barium borate, lithium triborate (LBO), potassium titanyl phosphate (KTP), KNbO₃ and MgO:LiNbO₃ are presented and compared with other crystals. In addition to a critical review, this paper also presents some new results for the analysis of frequency-conversion efficiency, experimental data of OPO in KTP, LBO for frequency conversion using temperature-tuned non-critical phase-matching and green lasers from the diode-pumped self-frequency-doubling crystal of neodymium yttrium aluminium borate.     

Efficient intracavity frequency-doubled Nd:GdVO4-LBO red laser at 670.5 nm under direct 888 nm pumping

We report an efficient laser emission on the 1341 nm ⁴ F _3/2 to ⁴ I _13/2 transition in Nd:GdVO₄ under the pump with diode lasers at 888 nm. Continuous wave (CW) 6.58 W output power at 1341 nm is obtained under 18.3 W of incident pump power; the slope efficiency with respect to the incident pump power was 45.1%. Moreover, intracavity frequency doubling with LiB₃O₅ (LBO) nonlinear crystal yielded 1.77 W of red light at 670.5 nm.     

All-solid-state continuous-wave frequency doubling Nd:LuVO4/LBO laser with 9.6 W output power at 672 nm

An efficient and compact red laser at 672 nm is generated by intracavity frequency doubling of a continuous wave (CW) laser operation of a diode pumped Nd:LuVO₄ laser at 1344 nm under the condition of suppression the higher gain transition near 1064 nm. With 38 W diode pump power and a frequency doubling crystal LBO, as high as 9.6 W of CW output power at 672 nm is achieved, corresponding to an optical-to-optical conversion efficiency of 25.3% and the output power stability in 8 h is better than 2.38%. To the best of our knowledge, this it the highest conversion efficiency of watt-level laser at 672 nm generated by intracavity frequency doubling of a diode pumped Nd:LuVO₄ laser at 1344 nm.     

All-solid-state dual end pumped YVO4:Nd/LBO blue laser with 21.8 W output power at 457 nm

It is reported the efficient compact deep-blue laser at 457 nm generation by intracavity frequency doubling of a continuous wave (CW) laser operation of a diode-pumped YVO₄:Nd laser on the ⁴ F _3/2 → ⁴ I _9/2 transition at 914 nm. An LBO crystal, cut for critical type I phase matching at room temperature is used for second harmonic generation (SHG) of the laser. With dual end pump configurations at total incident pump power of 60 W, as high as 21.8 W of CW output power at 457 nm is achieved with 20-mm-long LBO. The optical-to-optical conversion efficiency is up to 36.3%, and the power stability in 8 h is better than 2.36%.     

Efficient generation of blue light by intracavity frequency doubling of a cw Nd:YAG laser with LBO

We report on the efficient room-temperature operation of ⁴F_3/2–⁴I_9/2 transition in a diode pumped Nd:YAG laser operating at 946 nm. An output power of 5.1 W and a slope efficiency of 23.6% at 946 nm have been obtained. Different LBO crystals of length 3×3×10 mm³, 3×3×15 mm³, 3×3×18 mm³ were selected as frequency doubling material for comparison. A maximum single-ended output power of 1.3 W at 473 nm was achieved by frequency doubling with an optical conversion efficiency of 5%. When the Nd:YAG rod was replaced by the one with high reflectivity coating at 473 nm on the pump side, the output power of blue light was almost twice that without high reflectivity coating for 473 nm at the same pump power level. Moreover, the theoretical optimum length of LBO crystal for intracavity frequency doubling was discussed, and the experimental results made a good agreement with it.     

LD end-pumped intracavity frequency doubling SESAM passively mode-locked picosecond lasers

A diode pumped Nd:YVO₄ semiconductor saturable absorber mirrors (SESAM) passive mode-locked intracavity frequency doubled laser was studied. A type I phase matching LBO frequency doubling crystal was inserted in the cavity. With a pump power of 4.5 W, a 140 mW output of frequency doubled beam was achieved with LBO, while the power of one fundamental frequency beam was 240 mW with repetition rate of 85 MHz, and pulse duration of 5.2 ps.     

LD泵浦Nd:YAG/LBO结构660 nm红光激光器

采用国产LD泵浦Nd:YAG晶体,通过谐振腔镜的膜系选择获得了Nd³⁺离子中波长为1319 nm的受激辐射振荡,首次用I类临界位相匹配LBO进行腔内倍频,实现了660 nm红色激光的高效倍频输出.当泵浦注入功率为800 mW时,660 nm激光基横模(TEM₀₀)输出功率为46 mW,光光转换效率高达5.75%.     

All-solid-state continuous-wave frequency doubling Nd:LuVO4/LBO laser with 9.6 W output power at 458 nm

An efficient and compact red laser at 458 nm is generated by intracavity frequency doubling of a continuous wave (CW) laser operation of a diode pumped Nd:LuVO₄ laser at 916 nm under the condition of suppression the higher gain transition near 1064 nm. With 30 W diode pump power and a frequency doubling crystal LBO, as high as 9.6 W of CW output power at 458 nm is achieved, corresponding to an optical-to-optical conversion efficiency of 32.0% and the output power stability in 8 hours is better than 2.35%. To the best of our knowledge, this it the highest conversion efficiency of watt-level laser at 458 nm generated by intracavity frequency doubling of a diode pumped Nd:LuVO₄ laser at 916 nm.     

Highly efficient continuous-wave intracavity frequency-doubled Nd:YVO4-LBO laser at 457 nm under diode pumping into the emitting level 4F3/2

The continuous-wave high efficiency laser emission of Nd:YVO₄ at the fundamental wavelength of 914 nm and its 457 nm second harmonic obtained by intracavity frequency doubling with an LBO nonlinear crystal is investigated under pumping by diode laser at 880 nm into emitting level ⁴F_3/2. 6.5 W at 457 nm with M ²=1.8 was obtained from a 5-mm-thick 0.4 at.% Nd:YVO₄ laser medium and a 15-mm-long LBO nonlinear crystal in a Z-type cavity for 18.6 W absorbed pump power. An optical-to-optical efficiency with respect to the absorbed pump power was 0.35. Comparative results obtained for the pump with diode laser at 808 nm, into the highly-absorbing level ⁴F_5/2, are given in order to prove the advantages of the 880 nm wavelength pumping.