共查询到19条相似文献,搜索用时 203 毫秒
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本文采用均方根梯度描述低频位相噪声,建立了合理的低频位相畸变模型,以Ⅰ/Ⅱ类角度失谐KDP晶体的高强度三次谐波转换为例,详细的研究了低频位相畸变对三倍频光聚焦特性的影响。研究结果表明,三倍频光的焦斑半径随着基频光低频位相畸变的均方根梯度增大而明显增大,并且在均方根梯度较大时与基频光的焦斑半径相近。 相似文献
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针对KDP晶体的TypeI+ TypeⅡ匹配方式的三倍频方案,采用理论模拟与实验研究相结合方式,从非线性耦合波方程组出发,编制了考虑衍射、离散、吸收和端面反射等物理因素的二维模拟计算程序.针对x、y方向均是六阶超高斯分布的入射基频光,功率密度在2~8 GW/cm2时,得到了TypeⅠ倍频晶体厚度11.8 mm、失谐角300 μrad,TypeⅡ混频晶体厚度9 mm、失谐角为0 μrad的优化参数,此时三倍频转换具有较大的动态范围和较高的效率. 在星光Ⅱ激光装置大厅建立了高强度三倍频实验研究平台,实验平台上基频光光束口径为Φ70 mm、功率密度为1~7 GW/cm2内可调、脉冲宽度约为0.8 ns.在实验平台上采用Φ100 mm能量卡计对基频光(1ω)、二倍频(2ω)和三倍频光(3ω)的能量进行测量,二、三倍频的外部转换效率可达60%以上;利用条纹相机对1ω光和3ω光的脉宽进行测量,脉宽变化基本为0.8 ns(1ω)和0.5 ns(3ω);采用512×512点阵的CCD对1ω光和3ω光的近场分布进行了对应测量,通过图像处理,得到描述光束质量的强度调制度和通量对比度值.基频光的远场发散角利用列阵相机进行监测,得到对应的1ω光光束发散角θ=0.3±0.06 mrad.在倍频晶体后5 m远处用哈特曼小孔阵列板测量基频光和三倍频光的波前分布,得其均方根(rms)分别为1.129 waves和0.425 waves.实验中,当入射基频光功率密度较高时,倍频晶体出现了明显的非线性自聚焦丝破坏现象.(OB11) 相似文献
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为了使谐波转换系统保持高效稳定的3次谐波转换,采用数值模拟的方法,研究了基频光脉冲波形对3倍频转换效率的影响,并对高斯脉冲和平顶脉冲的不同谐波转换特点作了详细分析.当基频光为高斯脉冲时,在3GW/cm2的输入条件下最佳的2倍频转换效率为56.8%,低于理论预计的66.7%.进一步计算了不同功率密度下,最佳2倍频转换效率与超高斯脉冲阶数的关系.当考虑空间走离效应,基频光时间和空间均为平顶分布时,最佳的2倍频转换效率为62%;若基频光时间为平顶分布、空间分布为高斯分布时,最佳2倍频转换效率为51%,进一步地偏离66.7%.结果表明,当基频光脉冲形状偏离理想的平顶分布时,适当地降低2倍频转换效率,可提高3倍频转换效率. 相似文献
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We show that very high-efficiency second- and third- harmonic conversions can be generated simultaneously in 1-D semiconductor photonic crystals that possess both chi(2) and chi(3) nonlinearities. This is theoretically demonstrated in a CdS-SiO2 photonic crystal. The total conversion efficiency can be as large as ~30% for both second- and third-harmonic generations in a small sample with ~14 mum thickness and an input power of ~300 MW/cm2. Such high conversion efficiency is the result of 1) the improved phase matching induced by the Kerr effect and 2) the formation of coupled localized states for the fundamental and second- and third-harmonic waves. From our calculation results, we have also observed the tristability of the output intensity as a function of the input power for each of the fundamental, second-harmonic and third-harmonic waves. The origin of the tristability can be understood from the merging of two bistabilities of the fundamental and higher harmonic waves. 相似文献
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The evolution of complex leaky waves in partially open gyromagnetic slotlines into complex modes in a shielded slotline is presented. Given a particular stratified gyromagnetic slotline with two sidewalls present, four types (Types I-IV) of guided structures are defined and investigated, depending upon the four possible combinations of top and bottom covers. The behavior of the complex solutions is discussed for the partially open gyromagnetic slotlines. Initially, the slotline of Type I, which lacks both top and bottom covers, shows that no coupling exists among various pairs of leaky waves. By adding only a top cover into Type I, the resultant slotline of Type II exhibits certain coupling between different sets of leaky waves. Similarly, by adding only a bottom cover into Type I, the resultant slotline of Type III shows that certain strong leaky waves of Types I and II now become weak leaky waves. From these numerical experiments, we deduce that the complex modes supported by Type IV, which is completely shielded, can be the result of the mode coupling of the two previously found leaky waves in Types II and III waveguides, respectively. Therefore, the formation of complex modes in shielded slotline is related to the effects of covering on mode coupling of the various leaky waves of the partially open slotlines 相似文献
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《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1971,59(11):1613-1613
Many problems associated with acoustical holography are caused by the large difference between the wavelength of the recording acoustic waves and the wavelength of the reconstructing light waves. These problems can be partially compensated for by reducing the size of the acoustical hologram. It is demonstrated that there is a value of the reduction ratio that produces a maximum image size with small aberrations. 相似文献
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《Microwave Theory and Techniques》1981,29(2):107-114
The reflection and the scattering properties of even TE and TM surface waves incident in an abruptly ended dielectric slab waveguide are analyzed. The discontinuity is regarded as a junction between two open waveguides namely the dielectric slab waveguide and the free space waveguide. The boundary conditions acting together with the orthogonality provide singular coupled integral equations on the discrete and the continuous wave amplitudes at the discontinuity. These singular coupled intergral equations with Cauchy kernels and infinite limits of integration are solved by iteration via the Neuman series. Numerical results are presented for the reflectivity of the even TE/sub 0/ and TM/sub 0/ fundamental modes, together with their mode conversion on even TE/sub 2/ and TM/sub 2/ in a slab where two guided modes can propagate. Reflectivity and mode conversion of higher order excitations are also investigated 相似文献
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本文研究了基频光脉冲波形对三倍频转换效率的影响,对高斯脉冲和平顶脉冲的不同谐波转换特点作了详细分析,研究结果表明,当基频光脉冲形状偏离理想的平顶分布时,适当地降低二倍频转换效率,可提高三倍频转换效率。当基频光为高斯脉冲时,在3GW/cm2的输入条件下最佳的二倍频转换效率为56.8%,低于理论预计的66.7%。进一步的,计算了不同功率密度下,最佳二倍频转换效率与超高斯脉冲阶数的关系。 相似文献
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A solid-state laser cavity is studied where the laser crystal aberrations are corrected by a diffractive optic element. The type of aberration and the location of the correction plate are found to significantly influence the modal performance of the cavity. The largest modal discrimination is obtained for axicon-like crystal aberrations and when the correction is performed close to the end mirror. An experiment is performed with a laser diode-pumped Nd:YVO4 laser. With no correction, a thermal aberration of approximately two waves is measured across the crystal. By using a diffractive corrector plate, the single-mode slope efficiency is increased by a factor of 4, and the total single-mode output power is increased by a factor of 3 相似文献
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Mohamed A.K. Pruvost J.-A. Ribet I. Lefebvre M. Rosencher E. Binks D.J. 《Quantum Electronics, IEEE Journal of》2001,37(2):290-295
Intracavity frequency doubling of a pulsed Ti:sapphire laser is shown to be well described by multimode rate equations nonlinearly coupled through the homogeneous gain linewidth of the amplifying medium. Hole burning in the fundamental wave spectrum is observed at the phase-matched frequency and is explained well by theory in terms of the dynamic depletion of the fundamental waves phase-matched to the nonlinear output mirror. The doubling conversion efficiency is shown to be greatly improved by injection seeding at the same frequency as the “spectral hole” with a low power continuous-wave-tunable laser diode. This leads, for the first time to our knowledge, to single-mode UV-tunable (380-410 nm) emission using this technique. Finally, the source is shown to exhibit a minimum yield at the coincidence between injection and exactly phase-matched wavelengths while maintaining high efficiency when injecting a few nanometers away from the phase-matching maximum 相似文献
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Jian WANG Junqiang SUN Qizhen SUN Weiwei ZHANG Zhefeng HU Xinliang ZHANG Dexiu HUANG 《中国光电子学前沿》2008,1(1)
An all-optical 40 Gbit/s tunable single-tosingle channel wavelength conversion is experimentally realized based on cascaded sum- and difference-frequency generation (cSFG/DFG) in periodically poled LiNbO3 (PPLN) waveguides. By employing two tunable filters to effectively suppress the amplified spontaneous emission (ASE) noise, both wavelength down- and upconversions are simultaneously observed. We also propose and verify a novel cSFG/DFG-based single-todual channel wavelength conversion by setting two pumps (pumpl, pump2) close to each other or pump2 and the signal close to each other. For the latter, two kinds of cSFG/DFG schemes are both demonstrated The dependence of the conversion efficiencies of two channel idler waves on pumpl wavelength is discussed.The wavelength relationships between two channel idler waves and the three incident waves are investigated in detail theoretically as well as experimentally. 相似文献