Thales

Centre National De La Recherche Scientifique

Thomson-csf

Ecole Normale Superieure De Cachan

Association Pour La Recherche Et Le Developpement De Methodes Et Processus Industriels “armines”

Ecole Normale Superieure Paris-saclay

Gilles Feugnet

Sylvain Schwartz

Jean-Paul Pocholle

François Gutty

Arnaud Brignon

Christian Larat

Didier Rolly

Francois Gutty

Fabien Bretenaker

Philippe Martin

Pierre Rouchon

Mehdi Alouini

Etienne Bonnaudet

Augustin Mignot

Jérome Bourderionnet

Bastien Steinhausser

Jean-Paul Pocholles

Eric L Allier

Christian L Arat

Muriel Schwarz

Noad Hamze El Badaoui

Schwartz Sylvain

Maxime Descampeaux

Aranud Brignon

The invention relates to an optical reception device for receiving a signal from an antenna array comprising:

Device for optically receiving a signal coming from a phased antenna array and associated antenna system

An iterative method for determining scattering coefficients of the cavity of a laser gyro in operation supporting two counter-propagating modes, comprises steps of: determining a set of variables dependent on characteristic physical quantities of the laser gyro, one reference variable per dependency relationship being selected from the variables; measuring values of the characteristic physical quantities of the laser gyro in operation; determining measured values of the variables; estimating, via an iterative method, estimated values of the coefficients minimising a discrepancy between the measured values of the reference variables and estimated values of the reference variables, which are estimated from the values of the coefficients and the measured values of the variables other than the reference variables; and determining estimated values of the scattering coefficients from the estimated values of the coefficients.

Method for estimating scattering coefficients of a laser gyro in operation and associated gyroscopic system

A passive resonant optical gyroscope comprising a cavity and operating with three frequencies comprises: a first injecting laser to inject a first optical beam into the cavity in a first direction; a second injecting laser to inject a second optical beam into the cavity in an opposite direction; a third injecting laser to inject a third optical beam into the cavity in one of the aforementioned directions, one laser amongst the injecting lasers having a master frequency, the two other injecting lasers, called the first and second slave lasers, respectively having a first slave frequency and a second slave frequency; a master servocontrol device; a first servocontrol stage comprising first and second slave devices; and a second servocontrol stage comprising first and second optical phase-locking devices respectively comprising a first and second slave oscillator to generate a first radiofrequency offset signal and a second radiofrequency offset signal.

Compact three-frequency resonant optical gyroscope

The general field of the invention is that of passive resonator gyros comprising an injection laser emitting an initial optical beam at a first frequency and a fiber optic cavity. The gyro according to the invention operates with three optical beams at three different optical frequencies. A first beam is injected in a first direction of rotation, the second and the third beam are injected in the contrary direction. The gyro includes three slaving devices maintaining each optical frequency at a specific mode of resonance of the cavity. The gyro includes means for measuring the frequency differences existing between the different frequencies. Combined together, these differences are representative of the length of the cavity and the angular rotational velocity of the cavity along an axis perpendicular to its plane.

Optical passive resonator gyro with three beams

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

A laser gyro having a solid-state amplifying medium and an optical ring cavity includes an assembly encompassing the optical cavity and able to experience an oscillating rotational motion, as well as at least one external optical device for longitudinal injection of energy into the solid-state amplifying medium. The laser gyro also includes a fixing assembly adapted for translationally and rotationally binding said assembly encompassing the optical cavity and said external optical device for longitudinal injection of energy.

Laser gyro having a solid-state amplifying medium and an optical ring cavity

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 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 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

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 is by its nature highly unstable. To reduce this instability, the invention proposes to introduce controlled optical losses into the cavity that depend on the polarization direction by placing in the cavity an optical assembly comprising a polarizing element, a first element exhibiting a reciprocal effect that acts on the polarization of the wave and a second element exhibiting a nonreciprocal effect that also acts on the polarization of the wave, at least one of these two effects being variable, and to electronically slave these losses to the difference in intensity between the counterpropagating modes. Several devices are described that implement either fixed reciprocal effects combined with variable nonreciprocal effects, or vice versa. These devices apply in particular to monolithic cavity lasers and especially to lasers of the neodymium-doped YAG type and also to fiber cavity lasers.

Stabilized solid-state laser gyroscope

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.

Growing community of inventors

Palaiseau, France

Gilles Feugnet