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Nonlinear Optics - Chapter 8

Spontaneous Light Scattering and Acoustooptics 8.1.Các tính năng của tán xạ ánh sáng tự phát Trong chương này, chúng tôi mô tả tự phát tán xạ ánh sáng, Chương 9 và 10 mô tả hiện tại của các kích thích quá trình tán xạ ánh sáng. Tán xạ ánh sáng tự nhiên, chúng tôi có nghĩa là tán xạ ánh sáng trong điều kiện như vậy mà các tính chất quang học của hệ thống tài liệu chưa sửa đổi bởi sự hiện diện của chùm ánh sáng tới. Chúng tôi được nhìn thấy trong hai chương tiếp theo mà các. | Chapter 8 Spontaneous Light Scattering and Acoustooptics 8.1. Features of Spontaneous Light Scattering In this chapter we describe spontaneous light scattering Chapters 9 and 10 present descriptions of various stimulated light-scattering processes. By spontaneous light scattering we mean light scattering under conditions such that the optical properties of the material system are unmodified by the presence of the incident light beam. We shall see in the following two chapters that the character of the light-scattering process is profoundly modified whenever the intensity of the incident light is sufficiently large to modify the optical properties of the material system. Let us first consider the light-scattering experiment illustrated in part a of Fig. 8.1.1. Under the most general circumstances the spectrum of the scattered light has the form shown in part b of the figure in which Raman Brillouin Rayleigh and Rayleigh-wing features are present. By definition those components of the scattered light that are shifted to lower frequencies are known as Stokes components and those components that are shifted to higher frequencies are known as anti-Stokes components. Table 8.1.1 lists some of the physical processes that can lead to light scattering of the sort shown in the figure and gives some of the physical parameters that describe these processes. One of these light-scattering processes is Raman scattering. Raman scattering results from the interaction of light with the vibrational modes of the molecules constituting the scattering medium. Raman scattering can equivalently be described as the scattering of light from optical phonons. 391 392 8 Spontaneous Light Scattering and Acoustooptics Figure 8.1.1 Spontaneous light scattering. a Experimental setup. b Typical observed spectrum. Table 8.1.1 Typical values of the parameters describing several light-scattering processes Process Shift cm-1 Linewidth cm-1 Relaxation Time sec Gain a m MW Raman 1000 5 10-12 5 X 10-5 .