Real-time image transmission and interferometry through a distorting medium using two phase conjugators

Single beam one-way imaging through a thick dynamic turbulent medium

A new method to record an image through a thick dynamic phase distorting medium by using a photorefractive LiNbO3 crystal is demonstrated. The method uses only one beam of light, the object light. By making use of the photorefractive fanning effect, gratings are formed in the LiNbO3 crystal through the interference between the object light and its own fanning light. Because the time scale of the distorting fluctuation is much shorter than the writing time of the LiNbO3 crystal, the fluctuated light does not induce any fanning. Therefore only the static portion of the image is recorded in the crystal, and the intensity distribution of the image can then be reconstructed at any later time.

One-way imaging with an aberrated reference beam

We demonstrate image reconstruction by way of four-wave mixing for a signal that makes a single pass through a distorting medium. Both the signal and the reference originate from the same source and propagate through the same disturbance. In the four-wave mixing process, phase aberrations are subtracted out. A read beam from a second source reconstructs the undistorted image, yielding a phase conjugate without a double pass through the disturbance. Good reconstructed image fidelity is demonstrated for static distortions if the phase mismatch between the signal and the reference beams is minimized. If there is significant phase mismatch, reconstructed image fidelity is poor. We show that this technique can also be used to measure the autocorrelation function of the disturbance when the mismatch between the signal and the reference in the four-wave mixing scheme is varied.

Image transmission through a thick dynamic distorter by the photorefractive fanning effect

A new method of one-way image transmission through a thick dynamic distorter without the need for a reference beam or four-wave mixing is demonstrated. In this method there are only one object beam and one sampling beam. The response time of the photorefractive crystal must be much longer than the fluctuation period of the dynamic distorter. Thus the crystal responds only to the time-averaged intensity pattern of a rapidly varying object beam. The images, reconstructed with high fidelity, are picked up through the photorefractive fanning effect.