Two-dimensional diffraction grating atomic interferometer and atomic interferometry method
Disclosed is an atomic interferometer including a source of atoms, a laser source and a magnetic field generating device, a polarizer, a system for adjusting a detuning between two optical frequencies of the incident laser beam, a two-dimensional diffraction grating arranged in such a way as to receive the incident laser beam and to form by diffraction at least three diffracted beams, a controller configured to select a combination of an optical frequency detuning, a polarization state and a magnetic field, the combination being adapted to select a first pair of laser beams among the pairs of beams formed from the incident laser beam and the diffracted beams, the pair of laser beams being applied in such a way as to interact with the cloud of atoms by multi-photon transitions and to detect an acceleration of the cloud of atoms along a measurement direction.
1. An atomic interferometer ( 100 ) comprising a source of atoms ( 1 ) adapted to generate a cloud of atoms, a laser source ( 2 ) configured to generate a source laser beam ( 10 ), a magnetic field generating device ( 6 , 61 , 62 , 63 ), the atomic interferometer ( 100 ) further comprising polarization means ( 4 ) configured to receive the source laser beam ( 10 ) and to generate an incident laser beam ( 11 ) polarized according to an adjustable polarization state, a system ( 3 ) for adjusting a detuning between two optical frequencies of the incident laser beam, a two-dimensional diffraction grating ( 5 ) arranged in such a way as to receive the incident laser beam ( 11 ) and to form by diffraction at least three beams ( 12 , 13 , 14 , 15 ) diffracted along at least three non-coplanar directions, the at least three diffracted beams being inclined with respect to the axis of the incident laser beam, a controller ( 20 ) configured to select a first combination of a first optical frequency detuning of the incident laser beam related to a first speed of the cloud of atoms, a first polarization state of the incident laser beam and a first magnetic field oriented along a determined direction with respect to the two-dimensional diffraction grating, the first combination being adapted to select a first pair of laser beams among the pairs of beams formed from the incident laser beam and the at least three diffracted beams, a difference between two wavevectors of the first pair of laser beams determining a first measurement direction, the first pair of laser beams being applied in such a way as to interact with the cloud of atoms according to a time sequence by multi-photon transitions and to form a first Mach-Zehnder atomic interferometer sensitive to an acceleration of the cloud of atoms along the first measurement direction.
2. The atomic interferometer ( 100 ) according to claim 1 , wherein the controller ( 20 ) is configured to select a second combination of a second optical frequency detuning of the incident laser beam related to a second speed of the cloud of atoms, a second polarization state of the incident laser beam and a second magnetic field with respect to the two-dimensional diffraction grating, the second combination being adapted to select a second pair of laser beams among the pairs of beams formed from the incident laser beam and the at least three diffracted beams, a difference between two wavevectors of the second pair of laser beams determining a second measurement direction different from the first measurement direction, the second pair of laser beams being applied in such a way as to interact with the cloud of atoms according to a time sequence by multi-photon transitions and to form a second Mach-Zehnder atomic interferometer sensitive to an acceleration of the cloud of atoms along the second measurement direction.
3. The atomic interferometer ( 100 ) according to claim 1 , wherein the two-dimensional diffraction grating ( 5 ) is a diffraction grating configured to generate by diffraction four diffracted beams in four non-coplanar directions.
4. The atomic interferometer ( 100 ) according to claim 1 , wherein the two-dimensional diffraction grating ( 5 ) is a diffraction grating configured to generate by diffraction three diffracted beams in three non-coplanar directions.
5. The atomic interferometer ( 100 ) according to claim 1 , wherein the two-dimensional diffraction grating ( 5 ) is of the polarization-maintaining type.
6. The atomic interferometer ( 100 ) according to claim 1 , wherein the polarization means ( 4 ) comprise a liquid crystal retarder, a Pockels cell or a polarization controller based on the deformation of a single-mode optical fibre.
7. The atomic interferometer ( 100 ) according to claim 1 , wherein the magnetic field generating device includes three pairs of electric coils ( 61 , 62 , 63 ) in Helmholtz configuration.
8. The atomic interferometer ( 100 ) according to claim 1 , comprising magnetic field gradient generating means ( 64 , 65 ) adapted to adjust the first speed of the cloud of atoms.
9. The atomic interferometer ( 100 ) according to claim 1 , wherein the system ( 3 ) for adjusting a detuning between two optical frequencies of the incident laser beam is adapted to adjust the first optical frequency detuning as a function of the first speed of the cloud of atoms.
10. The atomic interferometer ( 100 ) according to claim 1 , wherein the system ( 3 ) for adjusting a detuning between two optical frequencies of the incident laser beam comprises an electro-optic modulator and a radiofrequency source.
11. The atomic interferometer according to claim 2 , wherein the two-dimensional diffraction grating is a diffraction grating configured to generate by diffraction four diffracted beams in four non-coplanar directions.
12. The atomic interferometer according to claim 2 , wherein the two-dimensional diffraction grating is a diffraction grating configured to generate by diffraction three diffracted beams in three non-coplanar directions.
13. The atomic interferometer according to claim 2 , wherein the two-dimensional diffraction grating ( 5 ) is of the polarization-maintaining type.
14. The atomic interferometer according to claim 2 , comprising magnetic field gradient generating means adapted to adjust the second speed of the cloud of atoms.
15. The atomic interferometer according to claim 2 , wherein the system for adjusting a detuning between two optical frequencies of the incident laser beam is adapted to adjust the second optical frequency detuning as a function of the second speed of the cloud of atoms.
16. An atomic interferometry method comprising the following steps:
a) generating a cloud of atoms;
b) selecting a first polarization state of a laser beam incident on a two-dimensional diffraction grating and a first magnetic field oriented along a determined direction with respect to the two-dimensional diffraction grating;
c) launching ( 70 ) the cloud of atoms with a first speed and calculating a first detuning between two optical frequencies of the incident laser beam, the first optical frequency detuning being related to the first speed, to form a first combination of the first optical frequency detuning of the incident laser beam, the first polarization state of the incident laser beam and the first magnetic field, the first combination being adapted to select a first pair of beams among the pairs of beams formed from the incident laser beam and at least three diffracted beams formed by diffraction of the incident laser beam on the two-dimensional diffraction grating along at least three non-coplanar directions;
d) applying to the cloud of atoms the first combination of the first magnetic field, the first polarization state and the first detuning between two optical frequencies of the incident laser beam, in such a way as to select the first pair of laser beams, a difference between wavevectors of the first pair of laser beams determining a first measurement direction, the first pair of laser beams being applied in such a way as to interact with the cloud of atoms according to a time sequence of multi-photon transitions and to form a first Mach-Zehnder atomic interferometer sensitive to an acceleration of the cloud of atoms along the first measurement direction;
e) detecting ( 90 ) a signal representative of an acceleration of the cloud of atoms along the first measurement direction.
17. The atomic interferometry method according to claim 16 , wherein step a) is repeated, and further comprising the following steps:
f) selecting a second magnetic field and a second polarization state of the laser beam incident on the two-dimensional diffraction grating;
g) launching ( 70 ) the cloud of atoms with a second speed and calculating a second detuning between two optical frequencies of the incident laser beam, the second optical frequency detuning being related to the second speed, to form a second combination of the second optical frequency detuning of the incident laser beam, the second polarization state of the incident laser beam and the second magnetic field, the second combination being adapted to select a second pair of beams among the pairs of beams formed from the incident laser beam and the at least three diffracted beams;
h) applying to the cloud of atoms the second combination of the second magnetic field, the second polarization state and the second detuning between two optical frequencies of the incident laser beam, in such a way as to select the second pair of laser beams, a difference between wavevectors of the second pair of laser beams determining a second measurement direction, the second pair of laser beams being applied in such a way as to interact with the cloud of atoms according to a time sequence of multi-photon transitions and to form a second Mach-Zehnder atomic interferometer sensitive to an acceleration of the cloud of atoms along the second measurement direction;
i) detecting ( 90 ) a signal representative of an acceleration of the cloud of atoms along the second measurement direction.
18. The atomic interferometry method according to claim 16 , comprising a step of trapping and cooling the cloud of atoms to form a cloud of cold atoms ( 19 ) and preparing an initial quantum state of the cloud of cold atoms ( 19 ).
19. The atomic interferometry method according to claim 18 , wherein the trapping and cooling step comprises a magneto-optic trapping of the cloud of atoms by superposition of the incident laser beam ( 11 ) and the at least three diffracted beams ( 12 , 13 , 14 , 15 ) in an overlapping area ( 16 ) and by application of a quadripolar magnetic field adapted to form the cloud of cold atoms ( 19 ).