GAS CELL FOR AN ATOMIC SENSOR AND METHOD FOR FILLING A GAS CELL

• US 20180210403A1
• Filed: 07/13/2016
• Published: 07/26/2018
• Est. Priority Date: 07/16/2015
• Status: Active Grant

• Current Assignee: Centre National De La Recherche Scientifique, Universite De Franche-Comte
• Original Assignee: Centre National De La Recherche Scientifique, Universite De Franche-Comte
• Inventors: Maurice, Vincent, Passilly, Nicolas, Gorecki, Christophe
• Granted Patent: US 10,775,747 B2
• Time in Patent Office: Days
• CPC Class Codes: G01R 33/0047 Housings or packaging of magnetic sensors packaging of semiconductor devices H01L23/00; Holders
• CPC Class Codes: G04F 5/14 using atomic clocks
• CPC Class Codes: G04F 5/145 using Coherent Population Trapping
• CPC Class Codes: H03B 17/00 Generation of oscillations using radiation source and detector, e.g. with interposed variable obturator
• CPC Class Codes: H03L 7/26 using energy levels of molecules, atoms, or subatomic particles as a frequency reference

Abstract

The invention relates to a gas cell for an atomic sensor, comprising an optical cavity provided with at least one optical window (9) and fillable with a gas. The cell also comprises a sealing cup comprising a cavity mouth, a channel mouth, and a sealing access, as well as a membrane which hermetically closes the sealing access of the sealing cup. The membrane can be plastically deformed by heating so as to hermetically close the cavity mouth and/or the channel mouth, in such a way as to hermetically separate the optical cavity from the gas inflow channel.

Claims

1. A gas cell, in particular for inclusion in an atomic sensor such as an atomic clock, an atomic magnetometer, or an atomic gyro, associated with at least one laser emitting an incoming exterior laser beam striking the cell as well as with a photodetector for receiving an exterior laser beam exiting the cell, the laser beam having penetrated the cell, the cell comprising an optical cavity provided with at least one optical window and adapted to be filled with a gas,

the cell comprising

a sealing basin comprising

a cavity mouth adapted to allow the passage of gas between the sealing basin and the optical cavity,

a channel mouth designed to allow gas to enter the sealing basin via a gas inflow channel, and

a sealing access, and

a membrane hermetically closing the sealing access of the sealing basin, wherein the cell is arranged such that the membrane is capable of hermetically closing at least one among the cavity mouth and the channel mouth when said membrane is plastically deformed by heating, in such a way as to hermetically separate the optical cavity from the gas inflow channel.

2. The cell according to claim 1, further comprising a heating device in contact with the membrane, in particular a resistive element adapted to be traversed by an electric current or a layer of a material that is absorbent to at least one wavelength of light which is not absorbed by the membrane.

3. The cell according to claim 1, comprising a multilayer assembly comprising:

a shapeable plate—

or wafer—

shaped to present a recess opening into at least one opening, said recess being adapted to be filled with a gas, and at least one glass plate—

or wafer—

hermetically closing said opening of the recess to form the optical cavity provided with at least one optical window, the glass plate—

or wafer—

and the shaped plate—

or wafer—

with recess being arranged facing one another and sealed to one another, in particular by anodic bonding.

4. The cell according to claim 3, wherein the membrane is a portion of the glass plate—

or wafer—

, and in particular wherein the optical window and the membrane are formed by two portions separated from one another by a single glass plate—

or wafer—

.

5. The cell according to claim 3, wherein the shapeable plate—

or wafer—

is shaped to present a second recess forming the sealing basin and opening into at least a second opening forming the sealing access.

6. The cell according to claim 3, wherein the sealing basin and the membrane are formed in the glass plate—

or wafer—

, in particular wherein the glass plate—

or wafer—

comprises at least a first glass sub-layer and a second glass sub-layer which are superimposed and integrally secured, the sealing basin being formed in the first glass sub-layer, the membrane being formed in the second glass sub-layer.

7. The cell according to claim 3, wherein the glass plate—

or wafer—

comprises a first glass sub-layer and a second glass sub-layer and wherein the multilayer assembly further comprises an intermediate layer for anodic bonding, in particular of silicon, arranged between the first glass sub-layer (27a) and the second glass sub-layer so as to enable anodic bonding between the first glass sub-layer and the second sub-glass layer,

in particular wherein

the membrane is formed in the second glass sub-layer,

at least the cavity mouth is formed in the first glass sub-layer, and

the intermediate layer for anodic bonding is shaped to leave at least the optical window unobstructed.

8. The cell according to claim 3, wherein the gas inflow channel is formed in at least one among the shapeable plate—

or wafer—

and the glass plate—

or wafer—

, so as to traverse the entire thickness of said plate—

or wafer—

, in a manner perpendicular to a plane of extension of said plate—

or wafer.

9. The cell according to claim 1, wherein the membrane is glass, and in particular is a thinned portion of a glass plate—

or wafer—

.

10. The cell according to claim 1, wherein the membrane comprises a protrusion facing the sealing basin, in particular a protrusion on the inner face of the membrane, extending into the sealing basin.

11. The cell according to claim 1, wherein the sealing basin comprises a sealing area surrounding the channel mouth, planar and parallel to the non-deformed membrane, and adapted to form a hermetic contact with the membrane plastically deformed by heating so as to hermetically separate the optical cavity from the gas inflow channel.

12. The cell according to claim 11, wherein a distance between the non-plastically deformed membrane and the sealing area—

measured perpendicularly to said non-plastically deformed membrane and said sealing area—

is less than a hundred microns.

13. The cell according to claim 11, wherein a diameter of the sealing area of the sealing basin is greater than three times said distance between the non-plastically deformed membrane and the sealing area.

14. The cell according to claim 1, wherein a thickness of the membrane is less than 500 microns, preferably less than 200 microns.

15. The cell according to claim 1, comprising a gas source connected to the gas inflow channel and adapted to fill the optical cavity with a gas via the gas inflow channel and the sealing basin, by means of the cavity mouth and the channel mouth.

16. The cell according to claim 15, wherein the source comprises a source cavity connected to the gas inflow channel and a dispenser of alkali metal received in the source cavity and adapted to generate alkali vapor by heating.

17. The cell according to claim 1, comprising, in addition to the optical cavity, an additional cavity filled with an additional gas, adjacent to the optical cavity and separated therefrom by a wall intended to be pierced to enable mixing said additional gas with a gas contained within the optical cavity.

18. The cell according to claim 17, wherein the wall of the additional cavity is adapted to be pierced by a contactless action exogenous to the cell, in particular by interaction of a pulsed laser beam, a continuous laser beam, or an electric discharge, with the wall.

19. The cell according to claim 1, wherein the optical cavity is filled with a gas, and wherein the membrane is in a plastically deformed state in which the membrane hermetically closes at least one among the cavity mouth and the channel mouth, hermetically separating the optical cavity from the gas inflow channel.

20. A set of cells comprising a plurality of cells according to claim 1, wherein the gas inflow channels are connected to a single gas source, in particular wherein said plurality of cells forms an integral and rigid assembly adapted to be cut so as to separate the cells from one another.

21. The method for filling a cell with gas, wherein:

a cell according to claim 1 or a set of cells according to claim 20 is provided,

a gas source connected to the gas inflow channel of the cell or set of cells is provided,

the optical cavity is filled with gas from the source via the gas inflow channel and the sealing basin, by means of the cavity mouth and the channel mouth, and

the membrane is plastically deformed by heating so as to hermetically close at least one among the cavity mouth and the channel mouth, in such a way that it hermetically separates the optical cavity from the gas inflow channel.

22. A gas filling method according to claim 21, wherein the membrane is plastically deformed by heating an outer face of the membrane, said outer face being in particular a face external to the cell.

23. The gas filling method according to claim 21, wherein the membrane is plastically deformed by heating using a laser directed onto the membrane.

24. The gas filling method according to claim 21, wherein the membrane is plastically deformed by heating, by allowing an electric current to flow through a resistive element in contact with the membrane.

25. The gas filling method according to claim 21, wherein the source is a dispenser of alkali metal received within a source cavity connected to the gas inflow channel of the cell or set of cells, and wherein the optical cavity is filled by heating said dispenser.

26. The gas filling method according to claim 21, wherein, after the membrane is plastically deformed in order to hermetically separate the optical cavity from the gas inflow channel, the cell is detached from the gas source.

27. The gas filling method according to claim 21, wherein, after the membrane is plastically deformed in order to hermetically separate the optical cavity from the gas inflow channel, a wall separating the optical cavity from an additional cavity filled with an additional gas is pierced so as to mix said additional gas with a gas contained within the optical cavity.

28. The gas filling method according to claim 21, wherein a set of cells according to claim 18 is provided, and wherein, after having filled the optical cavity with gas from the source,

at least the gas cavities of the cells of the set of cells are brought to a temperature above a first predefined temperature, said first predefined temperature being greater than a cell operating temperature of the set of cells, and a cold region of the set of cells is brought to a second predefined temperature that is strictly less than the first predefined temperature,

the membrane of each cell of the set of cells is plastically deformed by heating while maintaining the temperatures of the gas cavities of the cells and the cold region of the set of cells, and

the gas cavities of the cells of the set of cells are cooled to the operating temperature of said cells.

29. A Method for creating a vacuum in a cell, wherein;

a cell according to claim 1 or a set of cells according to claim 20 is provided,

a pumping station connected to the gas inflow channel of the cell or set of cells is provided,

the pumping station is operated so as to suction gas contained in the optical cavity via the gas inflow channel and sealing basin, by means of the cavity mouth and channel mouth, and

the membrane is plastically deformed by heating so as to hermetically close at least one among the cavity mouth and the channel mouth, in such a way as to hermetically separate the optical cavity from the gas inflow channel.

30. The method for fabricating a cell according to claim 1, wherein

a shapeable plate—

or wafer—

and at least one glass plate—

or wafer—

is provided,

the shapeable plate—

or wafer—

is shaped, in particular is etched, to form a recess opening into at least one opening,

at least one among the shapeable plate—

or wafer—

and the glass plate—

or wafer—

is shaped, in particular etched, so as to form a gas inflow channel and a sealing basin comprising

a cavity mouth adapted to allow the passage of gas between the sealing basin and the optical cavity,

a channel mouth designed to allow gas to enter the sealing basin via the gas inflow channel, and

a sealing access,

a multilayer assembly comprising the shapeable plate—

or wafer—

and said at least one glass plate—

or wafer—

is formed such that

the opening of the recess is hermetically closed to form an optical cavity having at least one optical window and adapted to be filled with a gas, and

the sealing access is hermetically closed with a membrane capable of being plastically deformed by heating so as to hermetically close at least one among the cavity mouth and the channel mouth, in such a way as to hermetically separate the optical cavity from the gas inflow channel.

31. A atomic sensor comprising a cell according to claim 1, associated in a compact manner with a laser emitting an incoming exterior laser beam striking the cell, and with a photodetector for receiving an exterior laser beam exiting the cell.