Device for an atomic clock

• US 8,816,783 B2
• Filed: 09/01/2010
• Issued: 08/26/2014
• 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
• Primary Examiner(s): Gannon, Levi
• Application Number:
  US13/393,996
• Publication Number:
  US 20120212298A1
• Time in Patent Office: 1,455 Days
• Field of Search: 331/3, 331/94.1, 356/436, 356/437, 372/32, 372 70- 75
• 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 allowing a first portion of the laser beam to pass according to a predefined percentage and deflecting a second portion of the laser beam,

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

a gas cell passed through by the first portion of the laser beam of circular polarization,

a mirror sending the first portion of the laser beam back toward the gas cell,

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

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

a second photodetector being placed after the splitter in such a way that the second portion of the laser beam reaches said second photodetector without having passed through the gas cell.

2. The device as claimed in claim 1, which comprises a third photodetector, placed behind the mirror, said mirror being semi-transparent and allowing a portion of the laser beam to pass, said third 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 2, which comprises a first diaphragm placed between the splitter and the gas cell, the first diaphragm reducing the size of the laser beam.

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

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

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

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

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

9. The device as claimed in claim 1, wherein the second photodetector is used to measure and/or adjust the output power of the laser source.