Nonlinear periodically poled ridge LiNbO3 waveguides have been fabricated on silicon substrates. Components are micromachined with a precision dicing machine and/or by grinding or polishing steps. They show efficient second harmonic generation at telecommunication wavelengths with normalized conversion reaching 600%/W in a 20mm long device. Influence of geometrical non uniformities of waveguides due to fabrication process is asserted. Components characteristics are studied notably their robustness and tunability versus temperature.
In this paper we present a three dimensional numerical model, based on a Pseudo-Spectral Time Domain algo- rithm (PSTD), that simulates the propagation of light carrying an image through a scattering medium and the back propagation of the scattered light which is re ected back by a phase conjugate mirror, modelled thanks to the nonlinear optical process of three-wave-mixing. We show how the phase conjugate wave retraces the scattering path and retrieves the spatial information of the input image with a signal to noise ratio that depends on the lateral dimensions of the phase conjugate mirror and of the number of realizations cumulated. Moreover, we show that the image restoration is not precluded by the polarization change between the phase conjugate wave and the scattered light exiting the complex medium.
We show that phase-conjugation by three-wave mixing allows turbidity suppression through biological tissues with thicknesses up to 5 mm, at a near-infrared wavelength included in the therapeutic window. Because of the ultrafast character of the imaging process, a motion of the tissue, which mimics in vivo imaging, can be exploited to significantly improve the signal-to-noise ratio and the resolution of the restored images.
In this paper we present results of real-time imaging through biological tissues by means of nonlinear three-wave mixing phase conjugation process. Biological tissues with thicknesses up to 5 mm are used and the imaging process is performed at a near infrared wavelength included in the therapeutic window. Furthermore we show that real-time compensation of turbidity of biological tissues allowed with this method can be applied to scattering media in motion, with a significant improvement of the signal to noise ratio and resolution of the restored images.
Design, fabrication and test of an optofluidic device are presented. It is constituted of a circular waveguide crossing a
fluidic channel integrated in a monolithic LiNbO3 wafer. The fluidic channel is realized by precision sawing and the
optical waveguide is induced by photorefractive beam self-trapping controlled by the pyroelectric effect. The self-aligning
property of this latter writing technique allows both, efficient light coupling inside the channel and light
collection after channel crossing. It is shown that the refractive index of a liquid present in the fluidic channel can be
accurately evaluated by simple monitoring of the light transmitted through the waveguide.
We report semi-classical numeric simulations of the quantum spatial fluctuations in parametric amplification of images limited by the shot noise. Noiseless amplification of images is demonstrated by the use of a degenerate type 2 phase sensitive amplifier.
The picosecond parametric amplification of a polychromatic image with a wavelength bandwidth of 140 nm and a gain of 15 dB has been obtained in a type I, LBO crystal. Thirty per 30 points were resolved. These results are in good agreement with a numerical study of the phase-matching conditions around the collinear degeneracy where phase-matching is non- critical for the signal beam in angle as well as in wavelength.
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