La_3Ga_5SiO_(14)电光调Q的Nd∶LiYF激光器研究

报道了以Nd∶LiYF(Nd∶LYF)为增益介质、用硅酸镓镧(La3Ga5SiO14,LGS)晶体进行电光调Q的非稳腔调Q激光器的脉冲特性。Nd∶LiYF的两端按σ偏振1.053μm光的布儒斯特角切割,不需另加起偏镜,实现了单一偏振光振荡。LGS晶体电光Q开关插入损耗小(2%),抗光伤阈值高(950MW/cm2),与DKDP相比,具有不潮解等优点。当抽运能量为120J、重复率3Hz时,单脉冲输出能量为275mJ,脉冲宽度为8ns,动静比为76%,输出能量不稳定度小于3%,偏振度大于99%,光束发散角为0.7mrad。文中还对本激光器偏振特性、非稳腔设计、LiYF导热性能和热透镜效应补偿进行了分析,对LGS电光调Q开关工作性能、工作方式以及存在的问题也进行了分析。     

退压式La3Ga5SiO14晶体电光调Q Nd:YAG激光器激光性能研究

通过对硅酸镓镧(LGS)晶体旋光性与电光效应的交互作用的理论研究,推导出晶体旋光性和电光效应共同作用下的光强表示式I=1-4B2(Asin 2ω-Ccos 2ω)2.利用此表示式设计计算了旋光晶体LGS尺寸为8 mm×8 mm× 25 mm电光Q开关在1064 nm波长使用时的开关电压和偏振角分别为4995 V和27.3°.将理论研究得到的结论应用于LGS晶体电光调Q的Nd:YAG晶体激光器的实验研究中,实验结果与理论计算结果基本一致.得到输出能量为361 mJ,脉冲宽度为7.8 ns的脉冲激光输出.     

退压式La_3Ga_5SiO_(14)晶体电光调QNd∶YAG激光器激光性能研究

通过对硅酸镓镧(LGS)晶体旋光性与电光效应的交互作用的理论研究,推导出晶体旋光性和电光效应共同作用下的光强表示式I=1-4B2(Asin 2ω-Ccos 2ω)2。利用此表示式设计计算了旋光晶体LGS尺寸为8 mm×8 mm×25 mm电光Q开关在1064 nm波长使用时的开关电压和偏振角分别为4995 V和27.3°。将理论研究得到的结论应用于LGS晶体电光调Q的Nd∶YAG晶体激光器的实验研究中,实验结果与理论计算结果基本一致。得到输出能量为361 mJ,脉冲宽度为7.8 ns的脉冲激光输出。     

Easy-axis kagome antiferromagnet: local-probe study of Nd3Ga5SiO14

We report a local-probe investigation of the magnetically anisotropic kagome compound Nd3Ga5SiO14. Our zero-field muon spin relaxation (muSR) results provide direct evidence of a fluctuating collective paramagnetic state down to 60 mK, supported by a wipeout of the Ga nuclear magnetic resonance (NMR) signal below 25 K. At 60 mK a dynamics crossover to a much more static state is observed by muSR in magnetic fields above 0.5 T. Accordingly, the NMR signal is recovered at low T above a threshold field, revealing a rapid temperature and field variation of the magnetic fluctuations.     

La_3Ga_5SiO_(14)声光可调谐滤波器设计

分析了La3Ga5SiO14(简称LGS)既可以做成同向声光可调谐滤波器,又可以做成大孔径非同向声光可调谐滤波器。推导出超声波频率f和光波波长λo的调谐关系;计算出滤波器的光谱分辨率R和集光能力δiθ;光入射角iθ与衍射角θd、声入射角θa之间的关系。为LGS声光可调滤波器的实用化设计提供了充分可靠的理论依据。把LGS与TeO2声光可调滤波器的光谱分辨率和集光能力做了比较,认为LGS设计成同向声光可调谐滤波器既简便又实用。     

Photorefractive two-step recording in a piezoelectric La3Ga5SiO14 crystal doped with praseodymium

The first experimental verification to the authors' knowledge of efficient two-step recording in a photorefractive and piezoelectric crystal of La(3)Ga(5)SiO(14):Pr(3+) with cw laser light (I<20W/cm(2)) is reported. We found nonlinear behavior of the photorefractive sensitivity and photovoltaic current, indicating that the excitation process is connected to excitation of 4f(2) electrons of the Pr(3+) dopant through an intermediate level to the conduction band. This two-step nature of the photorefractive effect makes the crystal an exciting new candidate for applications in holographic storage.     

Excited state dynamics of Eu3+ in the partially disordered crystals La3Ga5SiO14 and La3Ga5.5Ta0.5O14

The spectroscopic properties of two partially disordered crystals, langasite (LGS) and langatate (LGT), doped with Eu³⁺ were investigated. The fluorescence lifetimes of the ⁵D₀ and ⁵D₁ excited levels are measured. The spectral overlapping between the luminescence from the ⁵D₀ and ⁵D₁ levels was eliminated using pulsed excitation at 532 nm and suitable delays in order to improve the precision of the calculation of the spectroscopic figures of merit R₀, R₂ (the areas of the electric-dipole transitions ⁵D₀→⁷F₀ and ⁵D₀→⁷F₂, respectively, divided by the area of the magnetic-dipole one—⁵D₀→⁷F₁). The maximum splitting of the ⁷F₁ level (ΔE) is calculated from the luminescence spectra and the B₂₀ crystal field parameter is determined. We obtain R₀(LGS)>R₀(LGT), R₂(LGS)<R₂(LGT), and ΔE(LGS)>ΔE(LGT), and we discuss these results taking into account structural data, covalency and J-mixing effects.     

LD-pumped high repetition rate Q-switched Nd:YVO4 laser by using La3Ga5SiO14 single crystal electro-optic modulator

A diode-end-pumped electro-optic (EO) Q-switched Nd:YVO4 laser operating at repetition rate of 10 kpps (pulses per second) was reported. A block of La3Ga5SiO14 (LGS) single crystal was used as a Q-switch and the driver was a metal oxide semiconductor field effect transistor (MOS-FET) pulser of high repetition rate and high voltage. At continuous wave (CW) operation, the slope efficiency of the laser was 46%, and maximum optical-to-optical efficiency was 38.5%. Using an output coupler with transmission of 70%, a 10-kpps Q-switched pulse train with 0.4-mJ monopulse energy and 8.2-ns pulse width was achieved, the optical conversion efficiency was around 15%, and the beam quality M2 factor was less than 1.2.     

La3Ga5SiO14晶体的介电性质、弹性与压电性质

研究了La3Ga5SiO14晶体的介电性质、弹性和压电性质，其中弹性和压电性质是利用高频振动模式通过谐振法测定的. 关键词： 介电性质 弹性 压电性质     

Crystal growth and optical properties of Tm:La3Ga5SiO14 single crystals

High optical quality Tm:La₃Ga₅SiO₁₄ single crystals with dopant concentration of 1 at. % Tm³⁺ ions were grown by the Czochralski method. The structure was studied by the X-ray powder diffraction method. The absorption spectrum and fluorescence spectrum of Tm³⁺:La₃Ga₅SiO₁₄ crystals were measured at room temperature. PACS 42.70.-a; 42.70.Hj; 61.10.Nz; 61.66.Fn; 78.20.-e; 78.90.+t; 81.10.-h