Abstract: The present invention relates to a method for assisting in the detection of elements in an environment, comprising: the acquisition of a first wide-field image of an environment by a first sensor (14A) having a first field of view and a first resolution, the generation of a fused image from first narrow-field images of the environment acquired by a second sensor (14B) having a second field of view strictly less than the first field of view and a second resolution finer than the first resolution, In response to the detection of a difference relating to an element on a second wide-field image acquired by the first sensor (14A), compared to the first wide-field image, the acquisition of a second narrow-field image imaging the difference, and the update the fused image with the second narrow-field image.

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: 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: 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 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.

Abstract: Disclosed is a frequency doubler having a quantum well semiconductor structure and a second-order non-linear susceptibility grating that can be used to amplify notably the frequency doubling. The grating can be recorded optically or electrically within the semiconductor structure and has a pitch in the plane of the structure. Such a frequency doubler finds particular application to optical recording or reading systems.

Abstract: A quantum well wave modulator comprises a central well sandwiched by two lateral wells. The central well is populated with electrons and the two lateral wells, having different constitutions, are coupled to the central well so as to modulate two light waves under the effect of the application of an electrical field perpendicularly to the structure in one direction or in the opposite direction.

Abstract: The detector can be used to detect a wave in the medium infrared range by controlling the detector through optical pumping by means of a near infrared wave. In this case, the detector has a quantum well structure consisting of alternating first layers and second layers, these materials being such that there is a potential well in the conduction band and the valence band of each first layer. The thickness of each first layer is such that the electrons of the conduction band have at least one permitted discrete level of energy, such that the difference in energy between this level and the bottom of the conduction band in the second layers is smaller than or equal to the energy corresponding to the frequency of the wave to be detected; and such that the difference in energy between the fundamental level permitted for the holes in the valence band and the fundamental level permitted for the electrons in the conduction band corresponds to a frequency close to the frequency of the control wave.

Abstract: A quantum well electromagnetic wave detector disclosed having a semiconductor structure including a stacking of layers of material wherein the widths of the forbidden gaps of the materials are used to obtain a profile of potential energy corresponding to the bottom of the conduction band for the electrons in such a way that a first layer has a relatively low energy level with second and third layers having an intermediate energy higher than the energy of the first layer and fourth and fifth layers having high energy greater than either the intermediate or the low energy levels.

Abstract: A modulator enables the modulation of a wave in the medium infrared range by means of a signal modulating the amplitude of another electromagnetic wave in the near infrared range. The modulator comprises: a central layer such that the electrons of the conduction band have at least two permitted discrete levels of energy, the energy difference of which corresponds to a frequency close to the frequency of the wave to be modulated, and such that the holes of the valence band have permitted levels of energy such that the difference in energy between the permitted fundamental level for the holes in the valence band and the permitted fundamental level for the electrons in the conduction band has a value close to that corresponding to the frequency of the control wave.

Abstract: A frequency shifter to shift the frequency of a guided wave in the medium infrared range comprises:an optical guide, formed by semiconducting materials, on the surface of which a diffraction grating is created by carriers photo-induced by a periodic illumination.standard optic means projecting, on the surface of the guide, two wave beams having different frequencies in the near infrared or visible range, to produce, by interference, a periodic illumination of the surface of the guide. This illumination induces photocarriers constituting a diffraction grating which is in translational motion at constant speed. This motion shifts the frequency of the diffracted wave by Doppler effect.