Flexible automated assembly of micro-optical elements (optical SMD)

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We demonstrate 2-mu m wavelength, wafer-fused InGa(Al)As/InP-AlGaAs/GaAs vertical-cavity surface-emitting lasers (VCSELs) emitting single-mode power of 0.5 mW at room-temperature with a threshold current of 4mA and side-mode suppression ratio of over 30 dB. Emission wavelength can be continuously tuned with current by similar to 5 nm without mode hopping with a tuning rate of 0.31 nm/mA. These features demonstrate the long wavelength VCSELs potential for gas sensing and other optical spectroscopy applicatio

As digital holography achieves numerical reconstruction of the complex wavefront diffracted by specimen, a numerical optics formalism has been developed: numerical filters replace pinholes in Fourier planes, numerical lenses allow aberrations compensation and image magnification.

An ammonia traces analyser based on photoacoustic spectroscopy is described. The system uses a CO2 laser and a properly designed resonant photoacoustic cell to achieve ammonia detection at sub-parts-per- billion (ppb) level. The instrument features unattended automatic on-line monitoring of ammonia with a detection limit of 0.1 ppb. Interferences from atmospheric CO2 and H2O are efficiently suppressed by a careful selection of the laser wavelength and a compensation of the water vapour signal made with a hi

High quality AlInN was grown near lattice-matched to GaN. It shows about 7% index contrast with GaN. AlInN is thus a promising alternative to AlGaN, as demonstrated by a 20-pairs AlInN/GaN distributed Bragg reflector with over 90% reflectivity. Light emitting diodes with active layers grown on top of AlInN/GaN multi-layers exhibit internal quantum efficiencies comparable to those of reference diodes grown directly on GaN buffer, this further demonstrate that AlInN material quality can meet the needs of opto

A new nondestructive method for measuring the spatial distribution of chromatic dispersion along an optical fiber is presented. It is based on using Brillouin optical time-domain analysis to probe the power distribution of the four-wave mixing generated by two continuous-wave lasers. The results obtained prove that this new method is capable of providing better performance than comparable techniques. Furthermore, sensing the variations of Brillouin gain maximum produces additional information about the fibe

Urotropin (U) and azelaic acid (AA) form 1:1 co-crystals (UA) that give rise to a rather complex diffraction pattern, the main features of which are diffuse rods and bands in addition to the Bragg reflections. UA is characterized by solvent inclusions, parasite phases, and high vacancy and dislocation densities. These defects compounded with the pronounced tendency of U to escape from the crystal edifice lead to at least seven exotic phase transitions (many of which barely manifest themselves in a different

An optical modulator is arranged to compensate for the thermo-optical modulating effects induced by charge-injection based phase modulators. It comprises first modulator means (3), that receive optical radiation (11, 21), direct it along an optical path, apply a first predetermined optical phase modulation by the injection of free charges into the optical path, and output optical radiation (13, 22) so modulated. Compensator means (4) apply, to optical radiation output from (13, 22), or to be received by, th

We have directly measured, under operating conditions, the distributions of carrier densities and temperatures in a gain-clamped semiconductor optical amplifier designed for operation at 1.55 mum. As expected, longitudinal spatial hole burning is much smaller than in conventional semiconductor optical amplifiers and the effects of gain clamping are clearly evidenced. The amplifier nevertheless shows a sizeable temperature increase for both the lattice and the carriers at high currents, which are attributed

We report on new developments of a technique, called Digital Holographic Microscopy (DHM), for the numerical reconstruction of digital holograms taken in microscopy, which allows simultaneous amplitude and quantitative phase contrast imaging. The reconstruction method computes the propagation of the complex optical wavefront diffracted by the object and is used to determine the refractive index and/or shape of the object with accuracies in the nanometer range along the optical axis. The method requires the

We present two digital image processing methods for image quality enhancement in Digital Holographic Microscopy (DHM). With the first method, the Fourier transform of an off-axis hologram is spatially filtered in order to eliminate the zero order of diffraction and the twin image. We show that this operation enhances the image contrast and the signal to background ratio. The second method describes an original technique to perform the apodization of the hologram with a transmission profile which follows a c

Diode-pumped solid body laser comprises an acoustic-optical modulator, a laser crystal, a delay plate and a crystal that doubles the frequency of the laser beam. Pulse lengthening is carried out by internal coupling of a doubler mechanism within the laser resonator Preferred Features: The end surface of the laser crystal is formed as an end mirror limiting the laser resonator. The mirror is highly reflective for the laser beam. Crystals of SiO2 or TeO2 are provided for the acoustic-optical modulator.

The study of semiconductor interfaces and of solid interfaces in general requires novel instrument capable to investigate the lateral fluctuations of properties on a microscopic scale. We present the first result of a major effort in that framework, whose main objective is the exploitation of the unique characteristics of free electron laser (FEL) infrared sources. The background was provided by our previous development of FEL-based techniques to measure interface barriers with high accuracy and reliability

Flexible automated assembly of micro-optical elements (optical SMD)

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2-μm wavelength range InGa(Al)As/InP-AlGaAs/GaAs wafer fused VCSELs for spectroscopic applications

Numerical Optics in Digital Holography

Ammonia monitoring at trace level using photoacoustic spectroscopy in industrial and environmental applications

AlInN as high-index-contrast material for GaN-based optoelectronics

Distributed measurement of chromatic dispersion by four-wave mixing and Brillouin optical-time-domain analysis

Urotropin azelate: a rather unwilling co-crystal

An optical modulator

Density clamping and longitudinal spatial hole burning in a gain-clamped semiconductor optical amplifier

Digital holography applied to microscopy

Spatial filtering and aperture apodization in digital holographic microscopy

Diode-pumped solid body laser used in ophthalmology comprises an acoustic-optical modulator, a laser crystal, a delay plate and a crystal that doubles the frequency of the laser beam

Interface applications of scanning near-field optical microscopy with a free electron laser