Contrast-enhanced, amplified optical imaging by photorefractive recycling

Summary form only given. Optical processing by means of high-pass filtering is a well-established technique of enhancing the contrast of an optical image. However, this procedure is energetically inefficient, because the power associated with the low spatial frequency components of the image is ordinarily discarded. Here we demonstrate a new technique of performing contrast enhancement in an energy efficient manner, by recycling the optical power ordinarily discarded using photorefractive two-beam coupling in barium titanate. In the demonstration of our technique, we convert a phase object (a fingerprint on a glass slide) to an intensity image while conserving much of the power in the beam used to illuminate the phase object. Our technique thus holds considerable promise for applications such as biomedical imaging of organic tissue, where the power that can be used to illuminate the object is necessarily limited.