Noncritically phase-matched second-harmonic generation in cesium lithium borate

Efficient generation of 236-nm light was demonstrated by use of noncritically phase-matched second-harmonic generation in cesium lithium borate. Noncritical phase matching provided approximately 20x the nonlinear drive for second-harmonic generation than beta-barium borate for 236-nm generation. The 236-nm wavelength is the fourth harmonic of a 946-nm Nd:YAG laser. Phase matching was accomplished at a crystal temperature of -15 degrees C.     

Efficient nonlinear frequency conversion in an all-resonant double- lambda system

We demonstrate efficient, pulsed, gas-phase, nonlinear frequency conversion in a quadruply resonant, double- Lambda system and, simultaneously, verify theoretical predictions of Rabi-frequency matching unique to absorbing nonlinear media. This system is used to up-convert ultraviolet light at 233 nm to the vacuum ultraviolet at 186 nm in atomic Pb vapor with small-signal conversion efficiencies exceeding 30% and with modest atomic density-length (NL) products (scale 10(14) cm(-2)) and optical power densities (10-100 kW/cm(2)).     

噁英鎓类高聚物薄膜非线性折射率的测量及其时间分辨研究

本文报道有机杂环化合物(口恶)英(钅翁)掺杂高聚物PMMA薄膜的光学特征,在600～1000nm波长范围内,透射率为80～90%,材料折射率n=1.554,利用反向传播简并四波混频法测得该薄膜的非线性光学系数x~(3)为10~(-10)e.s.u.,并观测到后向泵浦束被延迟情况下,前向泵浦光束与探测光束形成光栅瞬态弛豫时间分辨曲线,它的弛豫时间为30ps.     

Measurement of the thermal contribution to the nonlinear refractive index of air at 1064nm

The thermal contribution to the nonlinear refractive index of air at 1.064mum was measured with a high-finesse Fabry-Perot cavity and a 500-mW cw laser beam. At room temperature and pressure, the nonlinear refractive-index coefficient of air was found to be n(2)((th))=(-1.9+/-0.2)x10 (-14) cm(2)/W for a beam waist radius of 0.23 mm and was found to be independent of the relative humidity. The thermal nonlinearities of N(2) , O(2) , and CO(2) were also measured, and it was found that the dominant contribution to air is its O(2) content.     

Oscillations at a difference frequency in the middle and far infrareds in GaP semiconductor waveguides

The feasibility of oscillation at a difference frequency in the middle and far infrareds is considered under the condition of phase matching between a nonlinear polarization wave and a difference mode produced by two fundamental modes with a wavelength near 1 μm excited in a GaP dielectric waveguide. With 10-W short-wave modes propagating in a 100-μm-wide planar waveguide, the power of the difference mode can be as high as 300 μW at 1–8 THz at room temperature. When the GaP waveguide leans upon a silicon substrate, the power of the difference mode may reach 5 mW at 10–14 THz at the same temperatures.     

Dispersion of the nonlinear refractive index in sapphire

The nonlinear refractive index, n2, of sapphire was experimentally measured in the 550-1550-nm wavelength range by use of a picosecond Z-scan technique. It was found that in this spectral region the value of n2 decreases monotonically from approximately 3.3 x 10(-16) to approximately 2.8 x 10(-16) cm2/W. An empirical expression for the wavelength dependence of the nonlinear refractive index in the 270-1550-nm range was obtained.     

Quantum-phase resolved mapping of ground-state vibrational D2 wave packets via selective depletion in intense laser pulses

Applying 7 fs pump-probe pulses (780 nm, 4 x 10(14) W/cm2) we observe electronic ground-state vibrational wave packets in neutral D2 with a period of T=11.101(70) fs by following the internuclear separation (R-)dependent ionization with a sensitivity of Delta相似文献   

双轴晶体中二次谐波产生的最佳相位匹配条件

从二次谐波产生的理论出发，讨论了双轴晶体中二次谐波产生的相位匹配条件，推导了有效非线性光学系数的精确计算公式，以有机非线性光学晶体二苯甲酮为例，给出了对两种基波(1064μm和0808μm)二次谐波产生的相位匹配条件的数值模拟及相应的有效非线性光学系数的精确计算结果，并确定出相应的最佳相位匹配条件. 关键词： 二次谐波产生 最佳相位匹配 有效非线性光学系数 二苯甲酮晶体     

Plasma effect on the phase matching of high harmonic generation

By optimizing the phase matching condition of high harmonic generation(HHG) from a supersonic neon gas jet,the enhanced HHG in the region of 60-70 eV has been selected.Three-dimensional numerical calculation shows that plasma plays a significant role in the phase matching process of HHG in a supersonic gas jet with short medium length.Due to plasma formation,the harmonic emission decays as the laser intensity reaches over 3.5 × 10 14 W/cm 2.The plasma induces the broadening and blue shift of the HHG spectra,which provides a method for fine-tuning the harmonic wavelength.     

Accessing the optical nonlinearity of metals with metal- dielectric photonic bandgap structures

Metals typically have very large nonlinear susceptibilities (~10(6) times larger than those of typical dielectrics), but because they are nearly opaque their nonlinear properties are effectively inaccessible. We demonstrate numerically that a multilayer metal-dielectric structure in which the metal is the dominant nonlinear [chi((3))] material can have much larger intensity-dependent changes in the complex amplitude of the transmitted beam than a bulk sample containing the same thickness of metal. For 80 nm of copper the magnitude of the nonlinear phase shift is predicted to be as much as 40 times larger for the layered copper-silica sample, and the transmission is also greatly increased. The effective nonlinear refractive-index coefficient n(2) of this composite material can be as large as (3+6iota)x10(-9) cm (2)/W , which is among the largest values for known, reasonably transmissive materials.     

Terahertz frequency standard based on three-photon coherent population trapping

A scheme for a terahertz frequency standard based on three-photon coherent population trapping in stored ions is proposed. Assuming the propagation directions of the three lasers obey the phase matching condition, we show that stability of few 10(-14) at 1 s can be reached with a precision limited by power broadening to 10(-11) in the less favorable case. The referenced terahertz signal can be propagated over long distances, the useful information being carried by the relative frequency of the three optical photons.     

Highly efficient third-order optical nonlinearities in donor-substituted cyanoethynylethene molecules

We investigated the third-order nonlinear optical properties of several donor-substituted cyanoethynylethene molecules in the zero-frequency limit. We observed nonlinearities that are extraordinarily large relative to the small molecular mass of these molecules and that are within a factor of 50 from the fundamental limit. At a wavelength of 1.5 microm, the rotational average of the third-order molecular polarizability is 53 +/- 13 x 10(-48) m5 V(-2) (3.8 x 10(-33) esu) for the best molecule, which corresponds to 1.7 x 10(-48) m5 V(-2) per delocalized electron. The high nonlinear efficiency of these molecules is due to the compact two-dimensional conjugated system and the effective donor-acceptor substitution patterns.     

Large nonlinear optical response of polycrystalline Bi3.25La0.75Ti3O12 ferroelectric thin films on quartz substrates

We measure the nonlinear susceptibility of Bi(3.25)La(0.75)Ti(3)O(12) (BLT) thin films grown on quartz substrates using the Z-scan technique with picosecond laser pulses at a wavelength of 532 nm. The third-order nonlinear refractive index coefficient gamma and absorption coefficient beta of the BLT thin film are 3.1 x 10(-10) cm(2)/W and 3 x 10(-5) cm/W, respectively, which are much larger than those of most ferroelectric films. The results show that the BLT thin films on quartz substrates are good candidate materials for applications in nonlinear optical devices.     

共线和非共线模式下单光子探测器定标比对实验研究

采用相关光子法定标单光子探测器的量子效率对提高光学载荷的辐射定标准确度具有重要意义.利用355nm连续激光泵浦BBO晶体产生Ⅰ类自发参量下转换,在共线和非共线两种相位匹配模式下分别测量了单光子探测器雪崩光电二极管在736nm波段的量子效率.结果表明,共线和非共线两种模式测量结果的合成不确定度分别为0.71%和0.39%,相对偏差均优于0.4%,这两种模式都可以定标探测器量子效率,且具有很好的一致性.最后比较了两种模式定标探测器量子效率的优缺点,该研究为以后利用相关光子法对遥感器进行辐射定标提供了晶体相位匹配模式选择的依据.     

聚苯胺/NMP溶液的激光诱导自衍射

实验观察到526um基模高斯先来通过聚苯按/N-甲基-2-吮咯烷酮(NMP)溶液时,在这场处产生了多个同心衍射圆环。该现象可以用高斯光束通过非线性介质时产生的空间自相位调制来解释。理论分析表明,对于薄样品,光束横截面上产生的非线性附加相移近似于高斯分布。通过测量衍射环个数,可以估算出聚苯胺/NMP溶液(对526um的吸收系数为0.56cm^-1)的克尔常数γ≈4.4x10^-10m²/W.     

Thomson scattering measurements of saturated ion waves in laser fusion plasmas

We have measured the characteristics of saturated ion-acoustic waves in inertial confinement fusion plasmas. A 263-nm probe laser has been applied to simultaneous Thomson scatter on both ion-acoustic waves excited by thermal electrostatic fluctuations and by stimulated Brillouin scattering of a kilojoule laser beam of varying intensity. The Thomson scattering spectra show saturated ion-wave amplitudes for intensities above 5x10(14) W cm(-2) consistent with three dimensional nonlinear wave modeling.     

参变过程中的群速延迟对晶体匹配长度的影响

基于能量守恒和三波耦合波方程,建立了超短脉冲在参变过程中二次谐波产生时的I类和II类相位匹配条件、基波与谐波之间的群速延迟时间、以及群速失配对晶体长度限制的理论基础。以负单轴非线性光学晶体CsLiB6O10为例,分析和数值计算了超短脉冲宽度为100fs时,谐波的群速匹配长度随基波波长变化的规律。研究结果表明在I类相位匹配条件下,基波波长为642nm时,群速延迟最小,相应的群速匹配晶体长度最长为19.1mm;在II类相位匹配条件下,基波波长为767nm,群速延迟最小,群速匹配长度最长为0.89mm。     

紫外晶体CsLiB6O10混频允许参量范围的数值分析

模拟计算了CLBO晶体混频的相位匹配角、有效非线性系数、走离角、允许角和允许波长的理论曲线。通过与BBO晶体的比较，得到了CLBO晶体的混频作用具有走离角小、允许参量范围宽的结论。     

Structuring mechanism in a nonlinear fizeau interferometer: Two-dimensional effects and the bifurcation pattern

Forming is examined for a nonlinear Fizeau interferometer with two-dimensional feedback [1]. A previous paper [2] dealt with explaining the formation mechanism for simple optical structures and detailed interferometer an input beam parameters. Here we consider factors responsible for the rate of change in the phase shift u(x, y, t) in a beam cross section; the role of the nonlinearity is considered in detail, which determines the number of possible states of u(x, y, t), and the limits to the applicability of the approach are considered. Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 10–14, March, 1997.