Probe beam linearly polarized

After the sample has been excited, the probe beam propagates in the sample probing the modified index of refraction. We assume the probe beam linearly polarized at 45° with respect to the excitation beam in the xy plane. The expression of the laser beam before the sample has been reported in the appendix. After the beam has propagated through the sample, the anisotropic index of refraction produces a modification of phase, which is different for the probe components along x and y. Neglecting the effect of the induced birefringence (see appendix) on the probe envelope functions, , the expression for the probe electric field after the sample is... 

The optical Kerr effect is a phenomenon of the optical field-induced birefringence and refers to the linear birefiingence induced by a linearly polarized optical field. The pump and probe beams are polarized 45 to each other in optical Kerr effect experiments. The probe beam may be composed of two orthogonal linearly polarized beams, and the polarization of one beam is parallel to that of the pump beam. According to third-order optical nonlinearity, the pump beam-induced linear birefringence is given by [46]. 

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... 

The probe was always p-polarised. The polarisation of the pump could be varied continuously from a p-polarised state either to a circularly polarised state by rotating a quarter wave plate (12) placed after a polarizer (13) (geometry 1), or to a state in which the beam was linearly polarized at an angle to the plane of incidence (geometry 2). In the latter case a quarter wave plate (12) was placed in front of the polarizer (13) in order to make the... 

The noncollinear pump-probe experiment is depicted schematically in Fig. 13. The linearly polarized (P3) pump pulse is focused (LI) into the sample producing induced transmission changes. The polarization of the probe beam is adjusted to 45° relative to the pump with a half-wave plate (A./2) and a Gian polarizer (PI). By the help of an analyzer (P2) simultaneous detection of the parallel ( ) and perpendicular ( L) components of the energy transmission T(v, to) of the probe through the sample is installed. For blocked excitation (chopper, Ch) the sample transmission... 

For larger aggregates, stronger enhancement is expected. The work by Tanaka et al. [89] showed that silver nanoparticles simultaneously trapped by a NIR laser beam also tend to ahgn parallel to the linear polarization, and it exhibited pronounced SERS signal at a very low concentration of probe molecules, 10 " M pseudoisocyanine (PIC) excited by a separate laser beam, whereas no SERS appeared if the trapping laser was not focused in the solution. 

PI-1 and PI-2 films exhibit dichroic absorbance after polarized irradiation. Figure 4.15 shows polar plots of the absorbance of linearly polarized probe light (at 488 nm) as a function of the angle, between the polarization of the probe and irradiation light (532 nm 30 mW/cm ). Nonpolar orientation is clearly shown for both PI-1 (left) and PI-2 (right). The highest absorption is observed when the probe and irradiation beams have perpendicular polarizations,... 

Sum-frequency generation (SFG) at second-order and the nonlinear Raman spectroscopy BioCARS at fourth-order can also probe chiral molecules. They have no analog in linear optics. We show that both are only symmetry allowed in a fluid, if the fluid is chiral. However, in contrast to optical activity phenomena, these processes arise entirely from induced electric-dipoles (without magnetic or quadrupolar transitions) and they are not circular differential. All laser beams can be linearly polarized and no polarization modulation is required as the detection of a sum-frequency (yiz. five-wave mixing) photon is in itself a measure of the solution s chirality. Since an achiral solvent can not contribute to the signal, these techniques are sensitive, background-free probes of molecular chirality. The SFG... 

An intense linearly polarized beam is used to induce optical birefringence in the media, 8n = nii — n, which results on a change of polarization of the weaker probe... 

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