Wave front shaping, the ability to manipulate light fields both spatially and temporally, in complex media is an emerging field with many applications. This review summarizes how insights from mesoscopic scattering theory have direct relevance for optical wave control experiments and vice versa. The results are expected to have an impact on a number of fields ranging from biomedical imaging to nanophotonics, quantum information, and communication technology.

Light fields in complex media: Mesoscopic scattering meets wave control

Optical phase conjugation: principles, techniques, and applications

We report an original two-dimensional time-resolved direct imaging method for transillumination optical tomography that combines the time-gating and forward phase-conjugation properties of type II degenerate parametric amplification. An object with subcentimeter resolution embedded in 4-cm-thick chicken breast tissue was imaged with a signal-to-noise ratio of 2.

Two-dimensional time-resolved direct imaging through thick biological tissues: a new step toward noninvasive medical imaging.

Image parametric amplification and its applications are reviewed in this paper. Phase matching conditions allow the resolution to be determined and spatial frequency filtering to be performed. The phase conjugate idler image can be used to cancel aberrations. Then, time gating properties are applied to ultrafast imaging, imaging through diffusing media, and lifetime fluorescence imaging. Degenerate schemes permit polychromatic amplification as well as phase-sensitive amplification, which is proved to be noiseless with respect to spatial fluctuations at the quantum level. Finally, it is shown that the spatial fluctuations of the signal and the idler are subshot noise correlated.

Parametric Amplification of Images: From Time Gating to Noiseless Amplification

Broadband and polarization-insensitive phase conjugation, achieved based on difference-frequency generation in a second-order nonlinear composite consisting of stacked KTiOPO4 (KTP) plates, was exploited to restore blurred images due to phase distortion as a novel scheme. Due to the quasi-phase matching in the stacked KTP crystals, our result reveals that the image restoration is insensitive to the polarization direction and wavelength of the input beam.

Restoration of blurred images due to phase distortion based on polarization-insensitive phase conjugation in second-order nonlinear medium

Restoration of an image through an aberrant plate has been achieved by use of optical phase conjugation in a type??II parametric interaction in which the amplified signal and idler waves are reflected back through the aberrant medium. The resolution of the restored phase-conjugate images is equal to 0.18??mm, and the amplification gain is ?4 dB.

E. Guiot

Papers

Image restoration through aberrant media by optical phase conjugation in a type II three-wave mixing interaction.