共查询到18条相似文献,搜索用时 109 毫秒
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带受激布里渊散射池的位相共轭激光器输出的空间特性 总被引:1,自引:1,他引:0
本文应用传输矩阵的方法对受激布里渊散射位相共轭腔输出的空间特性进行了分析及编程计算,给出了各种参数下受激布里渊散射-位相共轭腔的传输光束轮廓图,同时给出了实验结果与之相比较,提出了设计受激布里渊散射共轭腔时应注意的问题及几种实用的受激布里渊散射位相共轭腔的腔型。 相似文献
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采用瞬态受激旋转拉曼散射(SRRS)模型,详细考虑了激光脉冲的位相变化、时间波形、泵浦光的衰减、斯托克斯光的非线性放大以及初始的随机斯托克斯散射场等诸多因素,研究了空间位相畸变对空气中长程传输过程中产生的SRRS效应的影响。研究结果表明:位相畸变对阈值条件和时间特性影响较小,而对光束质量影响较为明显;随着位相畸变的增大,光束的能量分布变得极不均匀,光束的光强对比度也明显变大,从而使激光光束质量变差,而且当传输距离达到阈值条件后,随着传输距离的增加,光束质量将进一步变差。 相似文献
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位相畸变激光束的谐波转换 总被引:4,自引:2,他引:2
首次在理论上研究了位相畸变激光束的谐波转换,从波动方程出发,应用空间频谱方法处理位相畸变光束的非线性耦合问题,建立了适用于位相畸变且空间光强不均匀光束的谐波转换的理论模型。 相似文献
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采用外部F-P腔自锁定单模量子阱半导体激光器,观察到强度噪声的压缩现象,并同时大幅度降低了位相起伏.在35MHz附近观察到19.3%的强度压缩,对应激光输出的压缩度为37.8%,在9kHz-100MHz范围内观察到约3个数量级的位相噪声降低.获得了近最小测不准态.
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针对激光系统对光束匀滑的需求,设计了高斯型连续相位板,并对其远场特性进行了研究。分别计算了相干长度为39,30,10和3 mm的高斯相位板远场光斑分布,结果显示相位板自身相关长度是决定远场能量分布的重要因素,当相干长度大于10 mm时,由于不满足各态历经条件,远场光斑分布能量分散。当相干长度小于10 mm后,由于满足各态历经条件,远场光斑能量将接近理想的高斯分布特性。通过数值计算模拟了相干长度为3 mm的连续相位板对畸变光束进行匀滑处理的过程,演示了束匀滑处理结果。通过比较匀滑前后远场光斑的能量分布,显示了畸变光束通过连续相位板后远场光斑能量分布变化情况,通过相位板后,光斑形状明显接近理想高斯分布情况。 相似文献
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The phase diversity wavefront sensor is one of the tools used to estimate wavefront aberration, and it is often used as a wavefront sensor in adaptive optics systems. However, the performance of the traditional phase diversity wavefront sensor is limited by the accuracy and dynamic ranges of the intensity distribution at the focus and defocus positions of the CCD camera. In this paper, a modified phase diversity wavefront sensor based on a diffraction grating is proposed to improve the ability to measure the wavefront aberration with larger amplitude and higher spatial frequency. The basic principle and the optics construction of the proposed method are also described in detail. The noise propagation property of the proposed method is also analysed by using the numerical simulation method, and comparison between the diffraction grating phase diversity wavefront sensor and the traditional phase diversity wavefront sensor is also made. The simulation results show that the diffraction grating phase diversity wavefront sensor can obviously improve the ability to measure the wavefront aberration, especially the wavefront aberration with larger amplitude and higher spatial frequency. 相似文献
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Phase diversity wavefront sensor is one of the useful tools to estimate the wavefront aberration, and it is often used as a wavefront sensor in adaptive optics system. However, the performance of the traditional phase diversity wavefront sensor is limited by the accuracy and dynamic ranges of the intensity distribution at focus and defocus positions of the CCD camera. In this paper, a modified phase diversity wavefront sensor based on a diffraction grating is proposed to improve the ability to measure the wavefront aberration with larger amplitude and higher spatial frequency. The basic principle and the optics construction of the proposed method are also described in detail. The noise propagation property of the proposed method is also analysed by using the numerical simulation method, and comparison between the diffraction grating phase diversity wavefront sensor and the traditional phase diversity wavefront sensor is also made. The simulation results show that the diffraction grating phase diversity wavefront sensor can obviously improve the ability to measure the wavefront aberration, especially the wavefront aberration with larger amplitude and higher spatial frequency. 相似文献
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双锥光纤滤波器的研制 总被引:4,自引:1,他引:3
实验研究了熔锥条件对双锥光纤滤波器的影响。提出一个高斯模型,预测锥的几何形状。获得了窄带带通双锥光纤滤波器以及带阻中心波长分别为135nm和1559nm的带阻双锥光纤滤波器。 相似文献
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Influence of the abdominal wall on the nonlinear propagation of focused therapeutic ultrasound
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This article theoretically studies the influence of
inhomogeneous abdominal walls on focused therapeutic ultrasound
based on the phase screen model. An inhomogeneous tissue is
considered as a combination of a homogeneous medium and a phase
aberration screen. Variations of acoustic parameters such as peak
positive pressure, peak negative pressure, and acoustic intensity
are discussed with respect to the phase screen statistics of
human abdominal walls. Results indicate that the abdominal wall can
result in energy loss of the sound in the focal plane. For a
typical human abdominal wall with correlation length of 7.9~mm and
variance of 0.36, the peak acoustic intensity radiated from a 1~MHz
transmitter with a radius of 30~mm can be reduced by about 14% at
the focal plane. 相似文献
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Feasibility of nonresonant third harmonic generation in thallium is investigated. The third order susceptibility, for driving
frequencies in the visible region, is calculated and the phase matching with Ar as buffer gas is investigated. Other related
quantities like coherence length, minimum pulse lengths required to get phase matching and power input requirements to achieve
50% conversion are also calculated. 相似文献