May 6 2014
Optical phase conjugation is a non-linear optical process, which is capable of time reversing the scattering process and healing the distortions in a wavefront. Phase conjugation is an interesting phenomenon that is capable of creating unusual characteristics. The operating principle is similar to that of holography.
Optical phase conjugation has been an active field since the 1970s. By the process of optical phase conjugation, the direction of the propagation of the wave can be reversed, and the phase can be varied.
Some of the other terminologies used to describe this phenomenon are wavefront reversal, retroreflection, and time reversal. This article will look into the working, experimental setup, and applications of the optical phase conjugation process.
Experimental Set-Up
The device that produces optical phase conjugation is called the phase conjugate mirror (PCM). A PCM may be defined as a mirror that reflects light back towards where it came from, in the same direction. The optical source is a pumped laser.
A total of four beams are used in the process of creating optical phase conjugation. Two pumping beams, a signal beam, and a probe beam. The two pumping beams are made to intersect with one another, while the probe beam is directed towards the intersection of the pumping beams.
The fourth beam is produced by the interaction of these three beams. Thus, the optical phase conjugation is created by the four-wave mixing method.
Working
The optical phase pumping phenomenon is similar to the way real-time holography works. In order to achieve optical phase conjugation, beams 1 and 2 need to be aligned anti-parallel to one another. This will automatically render beam 4 as the phase conjugate of beam 3. Thus, beam 3, when projected onto a mirror, will produce beam 4, which is the time-reversed reflection.
Applications
Some of the typical applications of optical phase conjugation phenomenon are listed below:
- Biological sample study
- Optical imaging
- Digital imaging
Sources and Further Reading