Thomson-csf

Thales

Thomson-csf Semiconducteurs Specifiques

Thomson Composants Militaires Et Spatiaux

Thompson-csf

Jean-Paul Pocholle

Michel Papuchon

Gilles Feugnet

Sylvain Schwartz

Claude Puech

Jean-Pierre Huignard

Dominique Delacourt

Eric Lallier

Claude Weisbuch

Daniel Dolfi

Daniel Kaplan

Carlo Sirtori

Thierry Debuisschert

François Gutty

Christian Larat

Didier Rolly

Francois Gutty

Jean-Luc Ayral

Borge Vinter

Martine Doisy

Martin Defour

Nakita Vodjdani

Patrice Jano

Mehdi Alouini

Etienne Bonnaudet

Stéphanie Molin

Emmanuel Marquis

Thibaut De Saxce

Julien Nagle

Augustin Mignot

Bernard Groussin

François-Xavier Doittau

Claude Carriere

Schwartz Sylvain

Jean-Marc Breteau

Loïc Morvan

Franck Lacassie

Bastien Steinhausser

Eric L Allier

Christian L Arat

Denis Rabault

The invention relates a power fiber laser system including at least one single-mode fiber laser, emitting at a signal wavelength, the fiber including at least one outer cladding and a core, in which the core of the fiber has a radially graded index. The fiber includes, at least over a part of its length, a geometrical section having a graded fiber-core radius that decreases between an input end of the section and an output end of the section, the core radius and the index variation between the cladding and the fiber at the input end being such that the normalized frequency at the signal wavelength is less than the normalized cutoff frequency at which the fiber becomes unimodal.

High-power laser fiber system

A laser gyro for measuring the angular velocity or the angular position relative to a defined rotation axis includes: an optical ring cavity; a solid-state amplifying medium; and a non-reciprocal magneto-optic device; which are arranged so that four linearly polarized propagation modes can propagate within the cavity, the magneto-optic device introducing a frequency bias between the modes propagating in a first direction and the modes propagating in the opposite direction. In the device, the cavity also includes a stabilizer device for stabilizing the intensity of the four propagation modes at substantially equivalent levels, said device comprising at least one optical element made of a non-linear crystal of the frequency-doubling type.

Multi-oscillator solid-state laser gyro passively stabilized by a frequency-doubling crystal device

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.

Solid state gyrolaser with controlled optical pumping

Solid-state gyrolaser having a device for stabilizing the intensities making it possible to maintain equilibrium of the two counter-propagating modes having at least a means for calculating a rotation measurement (&#x3a9;, I&#x3a9;) of the gyrolaser on the basis of the counter-propagating modes having a frequency difference (&#x394;&#x3bd;mes) between them, by assuming that the frequency difference (&#x394;&#x3bd;mes) between the two counter-propagating modes is induced only by the rotation of the cavity. The gyrolaser also includes a means for measuring the control command (Co), a means for storing a behavior model (Mo) of a frequency bias (&#x394;&#x3bd;b) induced by the device for stabilizing the intensities, as a function of the control command, a means for calculating the frequency bias (&#x394;&#x3bd;b) induced by the device for stabilizing the intensities, on the basis of the value of the control command (Co) and the model (Mo), a means for calculating the bias (&#x394;&#x3a9;b, &#x394;I&#x3a9;b) in the rotation measurement (&#x3a9;, I&#x3a9;), induced by the frequency bias (&#x394;&#x3bd;b), and a means for compensating for the bias (&#x394;&#x3a9;b, &#x394;I&#x3a9;b) in the rotation measurement (&#x3a9;, I&#x3a9;).

Stabilized solid-state gyrolaser

The general field of the invention is that of fiber-optic sensors comprising at least one measurement optical fiber having an optically pumped doped amplifying medium, the optical characteristics of which are sensitive to a physical quantity, the fiber having at least one Bragg grating. The fiber is designed so as to generate, in the amplifying medium, two optical waves having different optical frequencies that propagate in the same direction after reflection on the Bragg grating and are emitted by the amplifying medium, the two optical frequencies depending on the physical quantity. The two waves may be generated using either a birefringent polarization-maintaining fiber or a DBR (Distributed Bragg Reflector) laser cavity. Notably, this sensor may be used as a hydrophone.

Self-referenced optical fiber sensor and related sensor network

The field of the invention is that of solid-state laser gyros used for the measurements of rotation speed or relative angular positions. This type of equipment is notably used for aeronautical applications. The object of the invention is to complete the optical devices necessary to control the instability of lasers by specific optical devices enabling elimination of the dead zone and of population inversion gratings exiting in the amplifying medium. An 'all optical' solid-state laser is hence obtained without moveable parts, stable and without a dead zone. To this end, the laser gyro according to the invention comprises notably and optical assembly enabling a nonreciprocal optical phase-shift to be introduced between the counterpropagating modes; and control means allowing the phase-shift amplitude to be varied periodically around a mean value that is very approximately zero.

Solid-state laser gyro optically active through alternating bias

The general field of the invention is that of rate gyros, of the matter-wave type, allowing the measurement of a speed of rotation in a given direction of measurement. This type of rate gyro works by the Sagnac effect and uses ultracold atoms to perform the measurement. It necessarily comprises an atom trap allowing a cloud of ultracold atoms to be immobilized in a given configuration and means for separation-displacement-recombination of the cloud into two packets of atoms so as to make them trace out a given area. The device according to the invention combines both of these two functions onto one atom chip notably comprising a first conducting wire through which a DC current Iflows with adjustable intensity, a second conducting wire and a third conducting wire that are substantially parallel, within the region of the trap, to the first conducting wire and are disposed symmetrically on either side of this first wire, the second and the third wire carrying an AC current of the same amplitude and same frequency flowing in the same direction, the maximum amplitude and the frequency of said current being sufficient to create, within the atom cloud, a magnetic field of higher intensity than the magnetic intensity required for the separation of the atom cloud into two packets of atoms.

Matter-wave rate gyro integrated onto an atom chip and associated Accelerometer

The present invention relates to a method for antimissile protection of vehicles having a very short response time with practically no false alarms and not requiring the use of means such as decoys or conventional laser jammers, while providing the best possible protection. It is characterized in that at least one curtain of plasma filaments is created between these vehicles and the probable launch point of these missiles, this curtain being intended to blind the target-seeking device of the missiles.

Method for antimissile protection of vehicles and implementing device

The field of the invention is that of solid-state laser gyros used in inertial control units. However, there are certain technical difficulties in producing laser gyros of this type that are due partly to the fact that the counterpropagating waves interfere with each other in the amplifying medium. A laser gyro according to the invention comprises at least one solid-state amplifying medium and an optical ring cavity comprising first optical means for imposing a first linear polarization state common to the two counterpropagating optical waves at the entrance and exit of the zone containing the amplifying medium and second optical means for imposing, within the amplifying medium, a second linear polarization state on the first optical wave and a third linear polarization state on the second optical wave, these polarization states being perpendicular. Thus, all the drawbacks associated with interference are eliminated.

Solid-state laser gyro having orthogonal counterpropagating modes

A laser gyro includes a semiconductor medium and assembled discrete elements, thus offering the possibility of producing large cavities for achieving the desired precision. More precisely, the laser gyro includes an optical ring cavity and a semiconductor amplifying medium with an external cavity having a vertical structure. The semiconductor amplifying medium which is used in reflection includes a stack of plane gain regions that are mutually parallel, and the dimensions of the cavity being substantially are larger than those of the amplifying medium.

Semiconductor solid-state laser gyro having a vertical structure

The field of the invention is that of solid-state ring lasers or laser gyros. The laser gyro according to the invention comprises at least one optical cavity in the form of a ring and a solid-state amplifying medium which are designed so that two counterpropagating optical modes can propagate in opposite directions one with respect to the other inside said optical cavity and pass through the amplifying medium, said amplifying medium being coupled to an electromechanical device imparting on said amplifying medium a periodic translational movement along an axis substantially parallel to the direction of propagation of said optical modes. Thus, the population inversion grating, written by the standing wave into the amplifying medium, which disturbs the nominal operation of the laser gyro, is greatly attenuated.

Solid-state laser gyro with a mechanically activated gain medium

A laser cavity optical architecture of a solid-state laser gyro measures rotational velocity or angular position and is based on a global conservation of the scale factor so that each parameter varies with temperature and avoids optical mode hops.

Scale-factor stabilized solid-state laser gyroscope

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.

Laser active optronic system with improved detectivity

The field of the invention is that of solid-state laser gyros. One of the major inherent problems in this technology is that the optical emission of this type of laser is by nature highly unstable in terms of power. To reduce this instability, the invention proposes to introduce, into the cavity, optical gains controlled by the installation of an optical assembly comprising an anisotropic lasing medium, a first optical element and a second optical element exhibiting a nonreciprocal effect, each acting on the polarization of the counterpropagating optical modes, at least one of these two effects being variable, thus making it possible to introduce controlled optical gains that depend on the propagation direction of the counterpropagating optical modes. Several devices are described and employ either fixed effects of the element that are combined with variable nonreciprocal effects, or the reverse. These devices apply in particular to monolithic-cavity lasers.

Stabilized solid-state laser gyro and anisotropic lasing medium

The field of the invention is that of solid-state laser gyros. One of the major problems inherent in this technology is that the optical cavity of this type of laser gyro is by nature highly unstable. To reduce this instability, controlled optical are introduced into the cavity that depend on the direction of propagation by using acoustooptic devices. Several devices are described, employing different configurations of acoustooptic devices. These devices apply in particular to laser gyros having monolithic cavities, and in particular to neodymium-doped YAG laser gyros.

Solid-state gyrolaser stabilised by acousto-optic devices

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La Norville, France

Jean-Paul Pocholle