Propagation of modulated optical fields through saturable-absorbing media: a general theory of modulation spectroscopy
Propagation of modulated optical fields through saturable-absorbing media: a general theory of modulation spectroscopy
复制标题
调制光场通过可饱和吸收介质的传播：调制光谱的一般理论
DOI：
10.1364/josab.2.001444
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发表时间：
1985
影响因子：
1.9
通讯作者：
C. R. Stroud
中科院分区：
文献类型：
--
作者：
M. Kramer;R. Boyd;L. W. Hillman;C. R. Stroud
处理弱调制光束通过非线性材料的传播。代表这种光束的光场由强载波频率分量和两个弱的、对称移位的边带组成，它们组合在一起形成一个场，该场可以是纯调幅（AM）、调频（FM）或这两种调制形式的某种组合。结果表明，对于任何光学非线性，存在两种调制形式，它们具有调制形式在光束传播下不变的特性。如果将这些自然模式之一以外的调制形式注入非线性介质中，则调制形式将随着光束传播而改变，渐近地接近经历较低衰减的自然模式。对于非线性介质可以建模为两级原子集合的情况，给出了这些自然模式的显式表达式。对于谐振泵浦光束的特殊情况，自然模式对应于纯幅度调制和纯频率调制。这种形式提供了 AM 和 FM 领域的饱和光谱的一般描述。推导出纯 FM 光束由于与两能级原子介质相互作用而转换为 AM 光束的速率公式。我们还考虑了由于 AM 波与两能级原子共振相互作用的调制深度的传播而产生的变化。该形式主义预测光谱特征的存在，其形状敏感地取决于材料的内部弛豫过程。给出了玻璃中红宝石、紫翠玉和荧光素的实验光谱并进行了解释。
The propagation of a weakly modulated light beam through a nonlinear material is treated. The optical field representing such a beam consists of a strong carrier-frequency component and two weak, symmetrically displaced sidebands that combine to form a field, which may be purely amplitude modulated (AM), frequency modulated (FM), or some combination of these two modulation forms. It is shown that, for any optical nonlinearity, two modulation forms exist that have the property that the form of modulation is invariant under propagation of the beam. If a modulation form other than one of these natural modes is injected into the nonlinear medium, the modulation form will change as the beam propagates, asymptotically approaching the natural mode that experiences the lower attenuation. Explicit expressions for these natural modes are presented for the case in which the nonlinear medium can be modeled as a collection of two-level atoms. For the special case of an on-resonance pump beam, the natural modes correspond to pure amplitude modulation and pure frequency modulation. This formalism provides a general description of saturation spectroscopy for both AM and FM fields. Formulas are derived for the rate at which a pure FM beam is converted to an AM beam owing to its interaction with a two-level atomic medium. We also consider the variation that is due to propagation of the depth of modulation of an AM wave interacting resonantly with two-level atoms. The formalism predicts the existence of spectral features whose shape depends sensitively on the internal relaxation processes of the material. Experimental spectra are presented for ruby, alexandrite, and fluorescein in glass and are interpreted.