Abstract: Many applications require the use of lasers with short optical ray lengths. However, at present, there is no module that makes it possible to refine a ray from a light source in a satisfactory manner, in particular one from a semiconductor laser. The invention relates to a spectral refinement method (500), a device with refined spectral line (200) comprising at least one light source (210) and a spectral refinement module (100). The latter includes at least one first coupler (111), a Brillouin resonator (120) and a modulator (130).

Abstract: Many applications require the use of lasers with short optical ray lengths. However, at present, there is no module that makes it possible to refine a ray from a light source in a satisfactory manner, in particular one from a semiconductor laser. The invention relates to a spectral refinement method (500), a device with refined spectral line (200) comprising at least one light source (210) and a spectral refinement module (100). The latter includes at least one first coupler (111), a Brillouin resonator (120) and a modulator (130).

Abstract: An analysis system comprises a transmitting device (1.1) and a receiving device (1.2). The transmitting devices comprises means for illuminating an object (1.3), or a part of the object, by a first light beam (1.8) consisting of signals with two distinct frequencies and first orthogonal polarisation states. The receiving device comprises means (1.6) for detecting, in a second light beam with second polarisation states and resulting from the illumination of the object to be analysed by the first light beam, a signal at a beat frequency equal to a difference between the two frequencies of the first light beam; and means (1.7) for obtaining information relating to the depolarising or dichroic character of the object, or of the part of the object, according to the detection or not of a signal at the beat frequency.

Abstract: The invention concerns an oscillator generating a wave composed of a frequency of on the order of terahertz from a beat of two optical waves generated by a dual-frequency optical source. The oscillator includes a modulator the transfer function of which is non-linear for generating harmonics with a frequency of less than one terahertz for each of the optical waves generated by the dual-frequency optical source, an optical detector able to detect at least one harmonic for each of the optical waves generated by the dual-frequency optical source and transforming the harmonics detected into an electrical signal, a phase comparator for comparing the electrical signal with a reference electrical signal, and a module for controlling at least one element of the dual-frequency optical source with a signal obtained from the signal resulting from the comparison.

Abstract: In the field of the production of very high frequencies, for example from 1 gigahertz to several terahertz, by beating the frequencies of two laser beams together, a device includes a resonant optical cavity having very stable dimensions receiving the beams, with for each beam, an interrogation device of the resonant cavity supplying an electrical signal representing the difference in frequency between the light frequency of the beam and a resonance frequency of the resonant cavity. The frequency of each beam is servo controlled to minimize the frequency difference observed. The laser beams are produced by a dual-frequency laser producing two beams of different frequencies and orthogonal polarizations. A polarization separator is used for separate servo control of the beams according to polarization, and a polarizer is placed behind a main output of the resonant cavity producing an electromagnetic beam mixing the two polarizations and amplitude-modulated at the beat frequency.

Abstract: An analysis system comprises a transmitting device (1.1) and a receiving device (1.2). The transmitting devices comprises means for illuminating an object (1.3), or a part of the object, by a first light beam (1.8) consisting of signals with two distinct frequencies and first orthogonal polarisation states. The receiving device comprises means (1.6) for detecting, in a second light beam with second polarisation states and resulting from the illumination of the object to be analysed by the first light beam, a signal at a beat frequency equal to a difference between the two frequencies of the first light beam; and means (1.7) for obtaining information relating to the depolarising or dichroic character of the object, or of the part of the object, according to the detection or not of a signal at the beat frequency.

Abstract: Techniques for identifying images of a scene including illuminating the scene with a beam of 3 or more wavelengths, polarized according to a determined direction; simultaneously acquiring for each wavelength an image X//(?i) polarized according to said direction and an image X?(?i) polarized according to a direction perpendicular to said direction, X?(?i) being spatially distinct from X//(?i); calculating for each wavelength an intensity image which is a linear combination of X//(?i) and X?(?i), providing an intensity spectrum for each pixel; calculating for each wavelength a polarization contrast image on the basis of an intensity ratio calculated as a function of X//(?i) and of X?(?i), providing a polarization contrast spectrum for each pixel; and calculating a spectro-polarimetric contrast image of the scene, each pixel of this spectro-polarimetric contrast image calculated based on the intensity spectrum and the contrast spectrum of the pixel considered.

Abstract: The invention concerns an oscillator generating a wave composed of a frequency of on the order of terahertz from a beat of two optical waves generated by a dual-frequency optical source (10). The oscillator comprises: a modulator (12) the transfer function of which is non-linear for generating harmonics with a frequency of less than one terahertz for each of the optical waves generated by the dual-frequency optical source, an optical detector (14) able to detect at least one harmonic for each of the optical waves generated by the dual-frequency optical source and transforming the harmonics detected into an electrical signal, a phase comparator (15) for comparing the electrical signal with a reference electrical signal, means (16) for controlling at least one element of the dual-frequency optical source with a signal obtained from the signal resulting from the comparison.

Abstract: In the field of the production of very high frequencies, for example from 1 gigahertz to several terahertz, by beating the frequencies of two laser beams together, a device includes a resonant optical cavity having very stable dimensions receiving the beams, with for each beam, an interrogation device of the resonant cavity supplying an electrical signal representing the difference in frequency between the light frequency of the beam and a resonance frequency of the resonant cavity. The frequency of each beam is servo controlled to minimize the frequency difference observed. The laser beams are produced by a dual-frequency laser producing two beams of different frequencies and orthogonal polarizations. A polarization separator is used for separate servo control of the beams according to polarization, and a polarizer is placed behind a main output of the resonant cavity producing an electromagnetic beam mixing the two polarizations and amplitude-modulated at the beat frequency.

Abstract: The general field of the invention is that of gyrolasers comprising at least one ring-shaped optical cavity comprising at least three mirrors, a solid state amplifying medium pumped by a laser diode whose optical emission power is determined by a current supply source, the cavity and the amplifying medium being such that two so-called contra-rotating optical modes propagate in opposite directions to each other within the said optical cavity, the gyrolaser being a class B gyrolaser, the gyrolaser also comprising means of measuring the difference in optical frequency existing between the two optical modes. The gyrolaser comprises means of measuring the total optical power circulating in the optical cavity and first means of control of the current delivered by the supply source in such a way as to maintain the total optical power substantially constant in a narrow spectral band centred on the relaxation frequency of the laser.

Abstract: Techniques for identifying images of a scene including illuminating the scene with a beam of 3 or more wavelengths, polarized according to a determined direction; simultaneously acquiring for each wavelength an image X//(?i) polarized according to said direction and an image X?(?i) polarized according to a direction perpendicular to said direction, X?(?i) being spatially distinct from X//(?i); calculating for each wavelength an intensity image which is a linear combination of X//(?i) and X?(?i), providing an intensity spectrum for each pixel; calculating for each wavelength a polarization contrast image on the basis of an intensity ratio calculated as a function of X//(?i) and of X?(?i), providing a polarization contrast spectrum for each pixel; and calculating a spectro-polarimetric contrast image of the scene, each pixel of this spectro-polarimetric contrast image calculated based on the intensity spectrum and the contrast spectrum of the pixel considered.

Abstract: The general field of the invention is that of gyrolasers comprising at least one ring-shaped optical cavity comprising at least three mirrors, a solid state amplifying medium pumped by a laser diode whose optical emission power is determined by a current supply source, the cavity and the amplifying medium being such that two so-called contra-rotating optical modes propagate in opposite directions to each other within the said optical cavity, the gyrolaser being a class B gyrolaser, the gyrolaser also comprising means of measuring the difference in optical frequency existing between the two optical modes. The gyrolaser comprises means of measuring the total optical power circulating in the optical cavity and first means of control of the current delivered by the supply source in such a way as to maintain the total optical power substantially constant in a narrow spectral band centred on the relaxation frequency of the laser.

Abstract: The subject of the invention is a laser comprising a semiconductor active medium with a population inversion lifetime ?c and a resonant cavity with a lifetime of the photons in the cavity ?p. The cavity includes means for being longitudinally monomode and means so that ?p>?c, such as for example a very long cavity, so as to obtain a laser with a very low intrinsic noise.