DEVICE FOR AN ATOMIC CLOCK

• US 20120212298A1
• Filed: 09/01/2010
• Published: 08/23/2012
• Est. Priority Date: 09/04/2009
• Status: Active Grant

• Current Assignee: Rolex SA
• Original Assignee: CSEM Centre Suisse D'Electronique et de Microtechnique SA
• Inventors: Lecomte, Steve, Haesler, Jacques
• Granted Patent: US 8,816,783 B2
• Time in Patent Office: Days
• US Class Current: 331/94.1
• CPC Class Codes: G04F 5/14 using atomic clocks
• CPC Class Codes: G04F 5/145 using Coherent Population Trapping
• CPC Class Codes: H01S 1/06 Gaseous , i.e. beam masers
• 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

A device for an atomic clock, including: a laser source (102) that generates a laser beam; a splitter (101) that makes it possible to divert and allow a portion of the laser beam to pass therethrough in accordance with a predefined percentage; a quarter-wave plate (105) that modifies the linear polarization of the laser beam into circular polarization and vice versa; a gas cell arranged on the circular polarization laser beam; a mirror (107) sending the laser beam back toward the gas cell (106); a first photodetector (108a), and a polarizer (103) arranged between the laser beam outlet and the splitter in order to protect the laser source from the retroreflections emitted by different optical elements constituting the device.

Claims

1. A device for an atomic clock comprising:

a laser source generating a laser beam,

a splitter for deflecting and allowing a portion of the laser beam to pass according to a predefined percentage,

a quarter-wave plate modifying the linear polarization of the laser beam into a circular polarization and vice versa,

a gas cell placed on the laser beam of circular polarization,

a mirror sending the laser beam back toward the gas cell, and

a first photodetector,

the splitter being placed between the laser source and the mirror, the quarter-wave plate being placed between the splitter and the mirror, the gas cell being placed between the quarter-wave plate and the mirror, in such a way that the polarization of the beam originating from the laser source via the splitter and arriving on the quarter-wave plate is linear according to the first angle and is modified by the quarter-wave plate into circular polarization, and so that the circular polarization of the beam reflected by the mirror and passing a second time through the gas cell is modified into linear polarization according to the second angle by the quarter-wave plate, the splitter directing a portion of the back-reflected beam toward the first photodetector,

wherein the device also comprises a polarizer placed between the output of the laser beam and the splitter in order to protect the laser source from the back-reflections originating from the various optical elements that make up the device.

2. The device as claimed in claim 1, it which comprises a second photodetector, placed behind the mirror, said mirror being semi-transparent and allowing a portion of the laser beam to pass, said second photodetector being used to control the optical frequency of the laser and/or to control the temperature of the cell.

3. The device as claimed in claim 1, which comprises a third photodetector placed after the splitter in such a way that a portion of the laser beam reaches said third photodetector without having passed through the gas cell.

4. The device as claimed in claim 1, which comprises a diaphragm placed between the splitter and the gas cell, this diaphragm reducing the size of the laser beam.

5. The device as claimed in claim 1, which comprises a second diaphragm placed between the splitter and the gas cell, this diaphragm reducing the size of the laser beam.

6. The device as claimed in claim 2, which comprises a third photodetector placed after the splitter in such a way that a portion of the laser beam reaches said third photodetector without having passed through the gas cell.

7. The device as claimed in claim 2, which comprises a diaphragm placed between the splitter and the gas cell, this diaphragm reducing the size of the laser beam.

8. The device as claimed in claim 3, which comprises a diaphragm placed between the splitter and the gas cell, this diaphragm reducing the size of the laser beam.

9. The device as claimed in claim 6, which comprises a diaphragm placed between the splitter and the gas cell, this diaphragm reducing the size of the laser beam.

10. The device as claimed in claim 2, which comprises a second diaphragm placed between the splitter and the gas cell, this diaphragm reducing the size of the laser beam.

11. The device as claimed in claim 3, which comprises a second diaphragm placed between the splitter and the gas cell, this diaphragm reducing the size of the laser beam.

12. The device as claimed in claim 4, which comprises a second diaphragm placed between the splitter and the gas cell, this diaphragm reducing the size of the laser beam.

13. The device as claimed in claim 6, which comprises a second diaphragm placed between the splitter and the gas cell, this diaphragm reducing the size of the laser beam.

14. The device as claimed in claim 7, which comprises a second diaphragm placed between the splitter and the gas cell, this diaphragm reducing the size of the laser beam.

15. The device as claimed in claim 8, which comprises a second diaphragm placed between the splitter and the gas cell, this diaphragm reducing the size of the laser beam.

16. The device as claimed in claim 9, which comprises a second diaphragm placed between the splitter and the gas cell, this diaphragm reducing the size of the laser beam.