Polarization orthogonal

A RIKES experunent is essentially identical to that of CW CARS, except the probe laser need not be tunable. The probe beam is linearly polarized at 0° (—>), while the polarization of the tunable pump beam is controlled by a linear polarizer and a quarter waveplate. The pump and probe beams, whose frequency difference must match the Raman frequency, are overlapped in the sample (just as in CARS). The strong pump beam propagating tlirough a nonlinear medium induces an anisotropic change in the refractive mdices seen by tlie weaker probe wave, which alters the polarization of a probe beam [96]. The signal field is polarized orthogonally to the probe laser and any altered polarization may be detected as an increase in intensity transmitted tlirough a crossed polarizer. When the pump beam is Imearly polarized at 45° y), contributions... 

When the electromagnetic radiation is incident at a boundary between two phases, part of the beam is reflected and part of it is transmitted into the second medium. Figure 9.1 shows the plane of incidence at the boundary formed by a transparent and an absorbing phase. The plane of incidence is the plane that contains the incident and reflected beams. Figure 9.1 shows that the incident beam can be envisaged as composed of two linearly polarized orthogonal components. These components, called p- and s-polarized components, are characterized by the directions of the electric field vectors in the plane of incidence and perpendicular to it, respectively. When the electric field of the radiation is located only in the plane of incidence, the beam is referred to as p-polarized. On the other hand, when the electric field of the radiation is located only in the plane perpendicular to the plane of incidence the beam is said to be s-polarized. 

In the simplest situation, termed type I phase matching, the incident radiation is polarized as an ordinary or an extraordinary ray, depending on the properties of the nonlinear material, and the harmonic radiation is polarized orthogonally to the incident radiation as shown in Fig. 6a. The wave-vector mismatch is then given by... 

Figure 9.37 Polar/orthogonal preform (Courtesy of Bally Ribbon Mills).

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