共查询到20条相似文献,搜索用时 359 毫秒
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Qinglong Meng Bin Zhang Sencheng Zhong Liguo Zhu 《Applied Physics A: Materials Science & Processing》2016,122(6):582
The damage threshold of lithium niobate crystal under single and multiple femtosecond laser pulses has been studied theoretically and experimentally. Firstly, the model for the damage threshold prediction of crystal materials based on the improved rate equation has been proposed. Then, the experimental measure method of the damage threshold of crystal materials has been given in detail. On the basis, the variation of the damage threshold of lithium niobate crystal with the pulse duration has also been analyzed quantitatively. Finally, the damage threshold of lithium niobate crystal under multiple laser pulses has been measured and compared to the theoretical results. The results show that the transmittance of lithium niobate crystal is almost a constant when the laser pulse fluence is relative low, whereas it decreases linearly with the increase in the laser pulse fluence below the damage threshold. The damage threshold of lithium niobate crystal increases with the increase in the duration of the femtosecond laser pulse. And the damage threshold of lithium niobate crystal under multiple laser pulses is obviously lower than that irradiated by a single laser pulse. The theoretical data fall in good agreement with the experimental results. 相似文献
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A simple and comprehensive electromagnetic theory uncovering complete picture of light transport in birefringent crystals 下载免费PDF全文
Jianbo Pan 《中国物理 B》2022,31(5):54201-054201
Birefringence production of light by natural birefringent crystal has long been studied and well understood. Here, we develop a simple and comprehensive rigorous electromagnetic theory that allows one to build up the complete picture about the optics of crystals in a friendly way. This theory not only yields the well-known refraction angle and index of ellipse for birefringence crystal, but also discloses many relevant physical and optical quantities that are rarely studied and less understood. We obtain the reflection and transmission coefficient for amplitude and intensity of light at the crystal surface under a given incident angle and show the electromagnetic field distribution within the crystal. We derive the wavefront and energy flux refraction angle of light and the corresponding phase and ray refractive index. We find big difference between them, where the phase refractive index satisfies the classical index of ellipse and Snell's law, while the ray refractive index does not. Moreover, we disclose the explicit expressions for the zero-reflection Brewster angle and the critical angle for total internal reflection. For better concept demonstration, we take a weak birefringent crystal of lithium niobate and a strong birefringent crystal tellurium as examples and perform simple theoretical calculations. In addition, we perform experimental measurement upon z-cut lithium niobate plate and find excellent agreement between theory and experiment in regard to the Brewster angle. Our theoretical and experimental results can help to construct a clear and complete picture about light transport characteristics in birefringent crystals, and may greatly facilitate people to find rigorous solution to many light-matter interaction processes happening within birefringent crystals, e.g., nonlinear optical interactions, with electromagnetic theory. 相似文献
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对LiNbO3: Fe晶体中二波耦合过程进行了动态观测.进一步探讨了LiNbO 3:Fe晶 体中弱光放大的物理机理.发现LiNbO3 : Fe晶体中二波耦合过程的弱光放大 对c轴指 向有明显的依赖关系,虽然光生伏打效应对光生载流子的迁移有主要贡献,但扩散机理的贡 献仍不可忽略.弱光最终得到放大是瞬态能量转移与扩散机理引起的能量转移的共同贡献.弱 光放大达到准稳态之后的下降过程为瞬态能量转移的时间指数衰减过程与光散射引起的能量 耗散的共同贡献.
关键词:
光折变效应
光放大
掺杂铌酸锂 相似文献
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Wenjie Xie Siu-Chung Tam Hongru Yang Jianhui Gu Gang Zhao Yee-Loy Lam Chan-Hin Kam 《Optics & Laser Technology》1999,31(5):387
It is important for laser designers to study the characteristics of heat transfer from the laser crystal slab to the coolant in high-power DPSS laser operations. We have simulated and obtained the optimum heat transfer coefficient and coolant flow rate for our cavity design, in which the circulating coolant is maintained at a constant temperature. It has been determined that the coolant temperature and the convective heat transfer coefficient (h) are important parameters in the thermal analysis. The coefficient h is affected by the coolant flow rate, the physical properties of the laser slab and the coolant and the pumping cavity geometry. Using analytical heat transfer equation, for cooling water temperature of 300 K, the optimum flow rate for our cavity geometry is found to be 390 cm3/s, corresponding to h=5 W/cm2 K. 相似文献
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The propagation of monochromatic laser radiation in a volume system of quantum dots (QDs) that are tunnel-coupled along one
axis is considered. The electron energy spectrum of the QD system is modeled in the tight-binding approximation with allowance
for the Coulomb interaction of electrons in the Hubbard model. The electromagnetic field of laser radiation in a QD system
is described quasi-classically by Maxwell equations; as applied to this problem, they are reduced to a non-one-dimensional
wave equation for the vector potential. As a result of the analysis of the wave equation in the approximation of varying amplitudes
and phases, an effective equation describing the electromagnetic field in a QD system is obtained and numerically solved.
The influence of the parameters of the system and the amplitude and frequency of the field of incident laser radiation on
the character of its propagation is investigated. Nonmonotonic dependences of the factor characterizing the laser beam diffraction
spread on the parameters of the electron energy spectrum of the system are obtained. 相似文献
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A compact continuous-wave blue laser has been demonstrated by direct frequency doubling of a laser diode with a periodically poled lithium niobate (PPLN) waveguide crystal. The optimum PPLN temperature is near 28 degrees C, and the dependence of waveguide crystals on crystal temperature is less sensitive than that of bulk crystals. A total of 14.8 mW of 488-nm laser power has been achieved. 相似文献
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Fuji T Rauschenberger J Apolonski A Yakovlev VS Tempea G Udem T Gohle C Hänsch TW Lehnert W Scherer M Krausz F 《Optics letters》2005,30(3):332-334
A new scheme for stabilizing the carrier-envelope (CE) phase of a few-cycle laser pulse train is demonstrated. Self-phase modulation and difference-frequency generation in a single periodically poled lithium niobate crystal that transmits the main laser beam allows CE phase locking directly in the usable output. The monolithic scheme obviates the need for splitting off a fraction of the laser output for CE phase control, coupling into microstructured fiber, and separation and recombination of spectral components. As a consequence, the output yields 6-fs, 800-nm pulses with an unprecedented degree of short- and long-term reproducibility of the electric field waveform. 相似文献
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采用解析法对Nd:YAG单晶光纤激光器热效应相关的光纤温度场分布进行研究。建立了Nd:YAG单晶光纤热模型,在单晶光纤所满足的边界条件下通过解析求解热传导方程,得到在高功率808 nm泵浦光抽运下产生946 nm激光的单晶光纤温度场分布,并与传统Nd∶YAG激光晶体的温度场进行比较,然后分别与同泵浦条件下的有限元数值方法的分析结果进行研究对比,最后分析泵浦光参数、单晶光纤参数等对温度场的影响。结果表明,功率为86 W的泵浦光入射至单晶光纤端面的最高温升仅为30.98℃,明显优于同泵浦条件下传统Nd∶YAG晶体的端面温升结果94.37℃,与有限元数值法得到的Nd:YAG单晶光纤19℃温升结果相比,该解析法结果更接近于实验的测量值31℃,能够更精确描述晶体光纤温度场。本文可对单晶光纤激光器热效应的精确研究提供一定参考,进而有利于提高单晶光纤激光器的性能。 相似文献
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In the present study, the hyperbolic heat conduction equation is derived from the Boltzmann transport equation and the analytical solution of the resulting equation appropriate to the laser short-pulse heating of a solid surface is presented. The time exponentially decaying pulse is incorporated as a volumetric heat source in the hyperbolic equation to account for the absorption of the incident laser energy. The Fourier transformation is used to simplify the hyperbolic equation and the analytical solution of the simplified equation is obtained using the Laplace transformation method. Temperature distribution in space and time are computed in steel for two laser pulse parameters. It is found that internal energy gain from the irradiated field, due to the presence of the volumetric heat source in the hyperbolic equation, results in rapid rise of temperature in the surface region during the early heating period. In addition, temperature decay is gradual in the surface region and as the depth below the surface increases beyond the absorption depth, temperature decay becomes sharp. 相似文献
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Potassium lithium tantalate niobate single crystals doped with erbium ions are grown by top-seeded solution growth method. The crystals are characterized by X-ray diffraction and differential thermal analysis. The refractive indices of the crystal are measured using ellipsometry method and fitted by Sellmeier equation. The as-grown crystals are tetragonal phase tungsten bronze-type structure with Curie temperature of 271.3 °C. Characteristic Er3 + absorption bands are observed from 350 to 1100 nm in ultraviolet–visible-near infrared absorption spectra. These crystals emit brightly green and red upconversion fluorescence under 975 nm LD laser excitation, and the steady state upconversion spectra are obtained at room temperature. The red emission intensity increases as the erbium ions concentration increases in crystals. Processes of excited state absorption and energy transfer are responsible for upconversion luminescence. The emission intensities are quadratic dependences on pump power from pump power dependence analyses and deduction of transition rate equation model. 相似文献
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The specific features revealed in the optical spectra of lithium niobate crystals at temperatures of 90 and 120–125°C can be attributed to the change in the electronic subsystem and the related isostructural transformation of the crystal lattice. In the near-IR range, the optical absorption spectra of lithium niobate crystals exhibit bands (1.43 eV) assigned to polarons of large radius with a binding energy of 0.48 eV. The decrease observed in the absorption coefficient at the maxima of these bands with an increase in the temperature to 160°C can be explained by the decay of polarons of large radius at these temperatures. 相似文献
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We report the numerical observation of discrete spatial solitons in a periodically poled lithium niobate waveguide array by applying an electrical field through electro-optical effect. We show that discrete spatial soliton can be controlled by applied voltage in the periodically poled lithium niobate. 相似文献
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Domas Paipulas Viačeslav Kudriašov Mangirdas Malinauskas Valerijus Smilgevičius Valdas Sirutkaitis 《Applied Physics A: Materials Science & Processing》2011,104(3):769-773
We report studies of the modifications induced inside lithium niobate and KDP crystals by Yb:KGW ultrafast laser pulses, having
300-fs pulse duration and operating at 100-kHz repetition rate. By focusing the laser beam with a 0.42 numerical-aperture
objective, we have recorded homogeneous volume Bragg gratings in the bulk of the niobate crystal that showed excellent diffraction
efficiencies, reaching up to 87%, and remained permanent after thermal annealing for one hour at 150°C. The refractive index
modification level was found to be 0.002 in lithium niobate. The results show that lithium niobate is a very promising crystal
candidate for microphotonics applications. On the contrary, in the KDP crystal no smoothly modified refractive index zones
were created. 相似文献
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基于中红外光源的气体光谱检测是新的痕量气体监测与分析方法,在大气监测领域具有重要的应用。构建了一套基于中红外DFG光源的甲烷气体光谱检测系统。该系统以1 550 nm和1 060 nm波段可调谐半导体激光器作为基频光源,采用PPLN晶体作为差频非线性变频器件,实现了3.3 μm处的窄线宽可调谐中红外光源输出。实验结果表明,当PPLN晶体工作温度为99.5℃时,闲频光的输出功率为112 μW,差频转换效率达到1.246 mW/W2。晶体的温度接受带宽为4.3℃,泵浦光波长接受带宽为5.3 nm。在此基础上,分别利用直接吸收法和谐波检测法获得了3 028.751 cm-1处的甲烷气体吸收光谱和二次谐波检测信号。 相似文献
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We systematically study the optimization of highly efficient terahertz(THz) generation in lithium niobate(LN)crystal pumped by 800 nm laser pulses with 30 fs pulse duration. At room temperature, we obtain a record optical-to-THz energy conversion efficiency of 0.43% by chirping the pump laser pulses. Our method provides a new technique for producing millijoule THz radiation in LN via optical rectification driven by joule-level Ti:sapphire laser systems, which deliver sub-50-fs pulse durations. 相似文献