Abstract: A semiconductor-based SWIR infrared detector sensitive to wavelengths shorter than about 2.5 microns comprises a stack of semiconductor layers based on III-V materials forming a PIN photodiode. The stack includes a naked electrical contact, called a lower electrical contact, serving as an optical window; and a detection layer sensitive to said wavelengths. The lower contact comprises at least one layer of indirect-bandgap III-V material(s) doped n-type, pseudomorphic or lattice matched with a substrate intended to serve as a temporary substrate possibly being made of a III-V material such as InP or GaAs or of silicon or germanium.

Abstract: A semiconductor-based SWIR infrared detector sensitive to wavelengths shorter than about 2.5 microns comprises a stack of semiconductor layers based on III-V materials forming a PIN photodiode. The stack includes a naked electrical contact, called a lower electrical contact, serving as an optical window; and a detection layer sensitive to said wavelengths. The lower contact comprises at least one layer of indirect-bandgap III-V material(s) doped n-type, pseudomorphic or lattice matched with a substrate intended to serve as a temporary substrate possibly being made of a III-V material such as InP or GaAs or of silicon or germanium.

Abstract: A laser active optronic system has an emission channel for the emission by an emission source of a laser beam which illuminates a target, and a receiving channel for receiving the wave backscattered by the target. An optical switching device is positioned in the receiving channel to receive the backscattered wave and has an optical gain medium and pumping means for pumping the gain medium. The gain medium is absorbent at the wavelength of the laser and becomes substantially transparent when it is pumped to allow the switching device to be actuated in the on mode or off mode respectively. A control unit for controlling the pumping means, allows the switching device to be actuated in the on mode in at least one temporal window of predetermined duration, triggered at a predetermined instant after the start of emission of the illuminating laser beam.

Abstract: The invention relates to a laser active optronic system with improved detectivity, especially an eye-safe optronic system. The system comprises a channel for the emission by an emission source of a laser beam illuminating a target and a channel for receiving the wave backscattered by the target. An optical switching device is positioned in the receive channel, said optical switching device receiving said backscattered wave and comprising an optical gain medium and pumping means for pumping said gain medium, said gain medium being absorbent at the wavelength of the laser and becoming substantially transparent when it is pumped, in such a way as to allow the switching device to be actuated in the on mode or off mode respectively. It further includes a control unit for controlling the pumping means, allowing the switching device to be actuated in the on mode in at least one temporal window of predetermined duration, triggered at a predetermined instant after the start of emission of the illuminating laser beam.

Abstract: The present invention relates to an optronic passive surveillance device, especially for infrared surveillance. It comprises a front optic (1) of given useful instantaneous field, means (2) for scanning a scene with a given total field of observation, means (3) for forming the image of the scene and means (4) for detecting said image. According to the invention, the detection means (4) comprise a two-dimensional matrix detector (41), the field of the detector along each of the dimensions being greater than or equal to said useful instantaneous field of the front optic along said dimension, and allow the acquisition, for each elementary area of the scene corresponding to the useful instantaneous field of the front optic, of N subimages formed on said detector (N?1), with a given integration time for each subimage.

Abstract: The present invention relates to an optronic passive surveillance device, especially for infrared surveillance.

Abstract: A device for harmonizing a laser beam path with an observation path for a target includes a laser that generates a laser beam; a first optical element that directs a first part of the laser beam toward the target along the laser beam path while directing a second part of the laser beam toward a conversion device; and a second optical element that directs a converted beam from the conversion device to a sensor that receives the converted beam and an image from the target. The conversion device includes a photoluminescent material that converts the second part of the laser beam into a converted radiation having a wavelength within a spectral band of the sensor, and an optical assembly that focuses the second part of the laser beam into the photoluminescent material and that collects at least a portion of the converted radiation to form the converted beam. The photoluminescent material can include photoluminescent ions such as erbium ions, or a semiconductor material such as indium arsenide.

Abstract: The invention relates to a modulation ratio amplification device, particularly for amplification at UHF. This device comprises means for making two optical waves, which are of the same amplitude but offset in frequency, interfere. These means may be a frequency converter, coupled to a continuous phase shifter; they may also involve two phase shifters: one continuous, the other varying sinusoidally over time. This type of device makes it possible greatly to amplify the desired modulation ratio, using an optical amplifier, given that the continuous background of the optical signal is suppressed.

Abstract: The invention relates to a frequency converter comprising a guide and a non-linear medium (NLM) in which the condition of phase matching between non-linear polarization and created waves is satisfied locally. The object of the invention resides in an additional layer C lying on the medium (NLM), the refractive index of which is such that it increases the conversion yield, for conversion of the incident waves to the waves created within the guide. This layer may be a symmetrization layer whose index is close to the index of the medium (NLM). The conversion yield may be further increased by means of an intermediate layer C.sub.ex, which lies between the layer C and the medium (NLM) and the index of which is close to that of the guide.

Abstract: Disclosed is a compact optical source capable of emitting wavelengths (notably in the blue spectrum) which it is difficult for standard laser diodes to achieve. This source has a laser (or laser diode) emitting at a wavelength .lambda.oi, a non-linear medium (NLM) in which the phase matching condition is achieved at a wavelength .lambda.o.sub.a belonging to the set of .lambda.o.sub.i values, a mirror M.sub.l transparent at .lambda.o.sub.i /2 and reflective at .lambda.oi placed at output of the medium (NLM) By reinjecting wavelengths .lambda.oi.noteq..lambda.oa into the laser, it is possible to lock the emission of the laser to .lambda.oa and thus set up a high-powered optical source .lambda.o.sub.a /2. Application: blue sources.

Abstract: Disclosed is a compact and coherent optical source using a laser that emits an incident wave at a wavelength .lambda.o.sub.i, a non-linear medium (NLM) in which the phase matching condition is verified at the wavelength .lambda.o.sub.a belonging to the set of .lambda.o.sub.i values. This optical source furthermore has two dichroic mirrors M1 and M2 at the points of entry into and exit from the non-linear medium that are highly transparent at the wavelengths .lambda.o.sub.i and highly reflective at the wavelengths .lambda.o.sub.i /2. Such a configuration advantageously enables the locking of the emission of the laser into the wavelength .lambda.o.sub.a, the recovery of a light wave at .lambda.o.sub.a /2 and, thus, the amplification of the emitted power at .lambda.o.sub.a /2. Application to blue sources.

Abstract: Disclosed is a non-linear optical device in which the non-linear medium comprises a circular surface on which the light beam to be processed gets reflected. A structure such as this can be used to resolve the difficulties of making mirrors of the cavity containing the non-linear medium.

Abstract: The invention pertains to an electromagnetic wave modulator comprising a quantum well semiconductor structure having two adjacent wells, the coupling of which is modified under the effect of an electrical field by the use of the phenomenon of anti-crossing of resonating levels. With this type of modulator, it is possible to attain 20% of modulation (as in the prior art) but with heightened sensitivity to the electrical field and a very short response time.

Abstract: A laser is capable of working at a wavelength L.sub.2 from an active material capable of generating radiating emissions at at least two wavelengths L.sub.1 and L.sub.2, through the presence of a semiconductor plate in the laser cavity. Notably, the laser can generate wavelengths ranging from 1.4 .mu.m to 2 .mu.m, a range in which the optical damage threshold of the eye is high, from an Nd.sup.3+ doped YAG having numerous radiating emission wavelengths ranging from 0.946 .mu.m to 1.8 .mu.m.

Abstract: A laser includes a gas enclosure placed in an optical cavity and receiving a pump beam to generate at least one first-order and one second-order Stokes wave. One of the mirrors of the cavity is transparent to wavelengths which are higher than the first-order Stokes wave.

Abstract: A coherent light power source comprising an oscillator and an amplifying optical fiber, both optically excited by the same pumping source, the beam of wave length L.sub.S output by the oscillator being amplified in the optical fiber.

Abstract: An electromagnetic wave detector has several stacks of layers of semiconducting materials. Each stack constitutes an asymmetrical quantum well with stepped barrier and has two energy levels, one of which is located beneath the energy level of the intermediate barrier step while the other is located above it. Means are used to apply an electric field to the structure.

Abstract: The device according to the invention is a frequency doubler comprising an optical index network which can be electrically controlled by two continuous electrodes, the network being created by the presence of (+P) polarization domains periodically separated by (-P) polarization domains, the electrodes being used to electrooptically compensate for variations in the index between the (+P) domains and (-P) domains.

Abstract: A method for the optical writing of information elements uses a material (Ma) that is highly non-linear optically, on which it is possible to record information elements with sizes several times smaller than the writing wavelength. Also disclosed is a method for the reading of information elements recorded on a material (Ma) deposited on a material (Mb) capable of being the site of a stimulated emission generating the reading of the recorded information elements. Applications: high definition television, digital sound.

Abstract: A semi-conducting structure delimits two quantal wells (CP1, CP2) connected across a barrier layer (CB). The application of an electric field to the structure makes possible the transfer of electrons from one of the wells to the other. The electron-hole pairs are created by a wave-pump, or by the doping of one of the wells. This makes possible, in particular, a dual control by means of the wave-pump and the electric field, thus creating an "AND"-function modulator.