Cross-polarized Wave Generation

Cross-polarized Wave Generation

Cross polarized wave (XPW) generation is a nonlinear optical process that can be classified in the group of frequency degenerate processes. It can take place only in media with anisotropy of third order nonlinearity. As a result of such nonlinear optical interaction at the output of the nonlinear crystal it is generated a new linearly polarized wave at the same frequency, but with polarization oriented perpendicularly to the polarization of input wave

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Simplified optical scheme for XPW generation is shown on Fig. 1. It consists of a nonlinear crystal plate (thick 1-2 mm) sandwiched between two crossed polarizers. The intensity of generated XPW has cubic dependence with respect to the intensity of the input wave. In fact this is the main reason this effect is so successful for improvement of the contrast of the temporal and spatial profiles of femtosecond pulses. Since cubic crystals are used as nonlinear media they are isotropic with respect to linear properties (there is no birefringence) and because of that the phase and group velocities of both waves XPW and the fundamental wave(FW) are equal:VXPW=VFW and Vgr,XPW=Vgr,FW. Consequence of that is ideal phase and group velocity matching for the two waves propagating along the crystal. This property allows obtaining very good efficiency of the XPW generation process with minimum distortions of the pulse shape and the spectrum.

Read more about Cross-polarized Wave Generation:  Description of The Process, For Additional Reading

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