01-08-2012, 10:58 AM
GENERATION OF OPTICAL PHASE CONJUGATE WAVE IN DYE SENSITIZED MEDIA
GENERATION OF OPTICAL PHASE.pptx (Size: 625.44 KB / Downloads: 32)
Nonlinear Polarization
Permanent Polarization
First order polarization:
Second order Polarization
Third Order Polarization
Third Order Polarization
The first term - describes a response at frequency 3ω that is due to an applied field at frequency ω. This term leads to the process of third harmonic generation
The second term - describes a non linear contribution to the polarization at the frequency of the incident field; this term hence leads to a non linear contribution to refractive index experienced by a wave at frequency ω. This intensity dependence of refractive index can result in important processes like Optical phase conjugation, Self focusing, Optical switching.. etc..
Optical Phase conjugation
Light beam interacting in a nonlinear material is reflected in such a manner as to retrace its optical path.
The image-transformation properties of this reflection are radically different from those of a conventional mirror
FOUR WAVE MIXING
A physical process that can generate a phase conjugate wave front.
Degenerate four wave mixing (DFWM)
DFWM
One of the most important processes used for OPC.
It’s a parametric process where the energy from two pump photons, one from each wave, is converted into one probe and one output signal photon.
The energy conservation requirement is obviously fulfilled in this case since all photons have the same frequency.
RESULT AND DISCUSSIONS
It was found that Lissamine green and Toluidine blue exhibits a third order optical nonlinearity thereby generating a phase conjugate wave by degenerate four wave mixing
It is inferred that the PC signal build up is not instantaneous but takes several minutes and it decays slowly with respect to time.
CONCLUSION
Observation of phase conjugate signal in glass doped with Lissamine green and Toluidine Blue dyes.
The dependence of PC wave generation on time of exposure was studied.
The phase-conjugate signal is found to have contributions from the DFWM and the holographic processes.