Self-starting optical phase conjugation

NONLINEAR OPTICAL PHENOMENA OBSERVED IN LIQUID CRYSTALS 

A hnearly polarized cw argon laser operating at the 5145 A line is electrically chopped to yield ptrlses of variable millisecond duration. It is focused onto the nematic hquid crystal sample with its electric field polarization vector E parallel to the director axis (i.e., an e wave). The transmitted beam is reflected, focused back on the sample, where it intersects the incident beam at a crossing angle in air of 3°. The polarization of the reflected beam is rotated so that it is orthogonal to the polarization direction of the incident beam (i.e., an o wave). 

As in most self-starting optical phase conjugation originating from speckle noise, the onset dynamics of the signal consist of two regimes an onset time r and 

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SELF-STARTING OPTICAL PHASE CONJUGATION (SSOPC)... 

I. C. Khoo, Hong Li and Yu Liang, "Self-Starting Optical Phase Conjugation in Dyed Nematic Liquid Crystal with Stimulated Thermal Scattering Effect," Opt. Letters, 18i. p. 3 (1993). 

Khoo, I. C., H. Li, and Y. Liang. 1993. Self-starting optical phase conjugation in dyed nematic liquid crystals with a stimulated thermal-scattering effect. Opt. Lett. 18 1490. 

Figure 12.15. Typical dynamics of self-starting optical phase conjugation process.

Figure 12.19. Schematic depiction of experimental set up used to demonstrate associative memory with self-starting optical phase conjugation, where a complete image is reconstructed from partial input data (78).

The observed dynamics of the self-starting phase conjugation process is governed by the optical nonlinearity and scattered noise amplitude [27], as well as the thermal grating build up time. Both the onset time and build up times are shortened as the input pump power is increased. The total time it takes for the signal to build up to the maximum can be as short as 0.5 ms, at a pump power of about 800 mWatt. These shortenings of the build up and onset times have also been observed as the sample temperature is increased towards T [25]. 

I. C. Khoo, "Self-Starting Phase Conjugation with Liquid Crystal," lEEE-Lasers and Electro-Optics Society Technical Meeting, San Jose, CA (November 1993). I. C. Khoo and Yu Liang, (to be published). 

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