聚焦高斯光束照射下平板laser的光谱奇异性和阈值增益
Spectral singularities and threshold gain of a slab laser under illumination of a focused Gaussian beam
摘要：
本文研究了均匀光学活性材料无限平板在高斯光束照射下，在薄透镜焦点处的光谱奇异性。我们将这种结构下高斯光束的场分布描述为在光轴附近传播的平面波，其相位和振幅随离光束中心的距离而变化。在此基础上，我们求出了板的传递矩阵。我们探讨的后果，这种配置上确定的阈值增益的活性介质和调谐相关的光谱奇异性的谐振频率。结果表明，光谱奇异性和阈值增益随离高斯光束中心的距离以及聚焦透镜的相对孔径而变化。因此，使用具有较高相对孔径的薄透镜，对应于共振的光谱奇异性向较高频率（较低波长）偏移。数值结果证实了理论研究结果
英文摘要：
We study spectral singularities of an infinite planar slab of homogeneous optically active material in focus of a thin lens under illumination of a Gaussian beam. We describe the field distribution of the Gaussian beam under this configuration as a plane wave propagated near the optical axis which its phase and amplitude vary with distance from center of the beam. Based on this approximation, we carry out the transfer matrix for the slab. We explore the consequences of this configuration on determining the threshold gain of the active medium and tuning the resonance frequencies related to spectral singularities. We show that the spectral singularities and the threshold gain besides that vary with distance from center of the Gaussian beam, also they change with relative aperture of the focusing lens. As a result, using a thin lens with higher relative aperture, the spectral singularities corresponding resonances shift to the higher frequencies (lower wavelengths). Numerical results confirm the theoretical findings
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