Light Focusing and Additive Manufacturing Through Highly Scattering Media Using Upconversion Nanoparticles

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An investigation of the parametric amplification and its coherent control in a semiconductor micro-cavity is presented. The time and angle resolved pump and probe experiments show that several ps after pumping parametric scattering is still phase coherent. The experimental data are in qualitative agreement with the numerical data obtained from a relatively simple theoretical model based on three polarisation components, pump, probe, and idler. This model also predicts that under particular circumstances, th

We present a tunable interference filter for infrared and visible light that scans the desired part of the optical spectrum within milliseconds. A single pixel detector measures serially the intensity at selected wavelengths. This concept avoids expensive linear detectors as used for grating spectrometers. The tunable optical interference filter is fabricated by a new porous silicon batch technology using only two photolithography steps. The refractive index of this filter microplate is gradually modulated

Off-axis holograms recorded with a CCD camera are numerically reconstructed with a calculation of scalar diffraction in the Fresnel approximation. We show that the zero order of diffraction and the twin image can be digitally eliminated by means of filtering their associated spatial frequencies in the computed Fourier transform of the hologram. We show that this operation enhances the contrast of the reconstructed images and reduces the noise produced by parasitic reflections reaching the hologram plane wit

Tests performed in different regimes reveal the interplay of two edge-enhancement mechanisms in radiological images taken with coherent synchrotron light. The relative weight of the two mechanisms, related to refraction and to Fresnel edge diffraction, can be changed in a controlled way. This makes it possible to obtain different images of the same object with complementary information. (C) 1999 American Institute of Physics. [S0021-8979(99)03720-2].

The high- and low-temperature forms, i.e., phase I (stable above 328 K) and phase II (stable below 328 K), of Cu8GeSe6 have been investigated by the powder X-ray diffraction method. Cu8GeSe6 II is hexagonal with A = 12.6438(2), C = 11.7570(1) Angstrom, Z = 6, and P6(3)cm, and its structure is considered to be a superstructure of the high-temperature form, Cu8GeSe6I (hexagonal, a = 7.3164(4) congruent to A/root 3, c = 11.7679(7) Angstrom, Z = 2, and P6(3)mc). Rietveld analysis of Cu8GeSe6 I (350 K) and II (2

A new way of measuring ozone and water vapor in the Planetary Boundary Layer (PBL) is proposed. The method is based on the simultaneous measurement of the Raman backscattering in the UV by O2, N2 and H2O, using a single pump beam at 266 nm. The ozone concentration is retrieved from the differential absorption of the N2 and O2 Raman backscattered signals, while the water vapor is measured using the classical Raman scheme. We present some preliminary results showing daytime ozone measurements in good correlat

Digital holograms are recorded by a CCD camera and are numerically reconstructed, in intensity and phase, by means of an algorithm which calculates their discrete Fresnel transform. By using a low-coherence source, the tomography of a 3D scene can be performed without lateral scanning with a depth resolution equal to the coherence length and a lateral resolution equal to the diffraction limit of the microscope objective used

Using a model structure consisting of a network of corner sharing tetrahedra, we calculate the infrared spectrum of amorphous SiO2 within a first-principles approach and find good agreement with experiment both for the positions and the intensities of the main peaks. In addition to the vibrational properties, this required the dynamical charge tensors, which were obtained applying the recent quantum polarization theory. The relative intensities in the spectrum depend sensitively on the charge tensors and th

The design and characterization of optical phantoms which have the same absorption and scattering characteristics as biological tissues in a broad spectral window (between 400 and 650 nm) are presented. These low cost phantoms use agarose dissolved in water as the transparent matrix. The latter is loaded with various amounts of silicon dioxide, intralipid, ink, bovine serum, blood, azide, penicillin and fluorochromes. The silicon dioxide and intralipid particles are responsible for the light scattering wher

We describe here a numerical application of the optical low- coherence holographic microscopy (OLCHM) technique. A low coherent source illuminates an object and the backscattered light interfere with a reference wave which optical path's length can be precisely adjusted. Holograms are recorded by a CCD camera and numerically reconstructed. With this technique optical tomography can be performed with a single scan along the optical axis. The transverse resolution of the reconstructed images mainly depends on

For holographic biopsy purposes, holograms of biological tissue samples have been recorded in vitro to establish the possibility of differentiating tissues on the holograms. With the use of specific absorbing dyes for staining tissues, the contrast has been improved. On the holograms, tissue architecture has been observed in the cortex of the kidney. Isolated epithelial cells could be seen with a distinct nucleus. Two distinct layers of the gray matter in the human brain have been differentiated. Finally, t

Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) has been established as a good and relatively sensitive method for qualitative analysis of powders and rough surfaces. The technique is non-destructive and high quality spectra can be easily obtained without extensive sample preparation. The capacity of the method for qualitative analysis of functional groups has been demonstrated in numerous fields. The potential of DRIFTS for quantitative analysis was recognized quite early as well. Howe

Light Focusing and Additive Manufacturing Through Highly Scattering Media Using Upconversion Nanoparticles

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Quantum kinetics of parametric polariton scattering in microcavities

Microspectrometer based on a tunable optical filter of porous silicon

Spatial filtering for zero-order and twin-image elimination in digital off-axis holography

Coherence-enhanced synchrotron radiology: Refraction versus diffraction mechanisms

Superspace-group approach to the phase transition of Cu8GeSe6

A Raman differential absorption lidar for ozone and water vapor measurement in the lower troposphere

Optical tomography by means of a numerical low-coherence holographic technique

Dynamical charge tensors and infrared spectrum of amorphous SiO2

Design and characterization of a phantom that simultaneously simulates tissue optical properties between 400 and 650 nm

Optical tomography at the microscopic scale by means of a numerical low coherence holographic technique

High-resolution holography and biopsy: Preliminary results

Spectroscopie FTIR quantitative de réflectance et transmittance diffuses