Atomic oscillator and interrogation method of coherent population trapping resonance

Patent metadata

Field	Value
Publication number	US-9444476-B2
Application number	US-201314420709-A
Country	US
Kind code	B2
Filing date	Aug 28, 2013
Priority date	Aug 30, 2012
Publication date	Sep 13, 2016
Grant date	Sep 13, 2016

Abstract

An atomic oscillator includes an alkali-metal cell in which alkali-metal atoms are enclosed, a light source which irradiates the atoms in the alkali-metal cell with laser beams, a photodetector which detects a light amount of the laser beams passing through the alkali-metal cell to enter the photodetector, and a controller which generates sidebands including a pair of laser beams with different wavelengths by performing frequency modulation of a carrier on the light source, causes the pair of laser beams with the different wavelengths to enter the alkali-metal cell, and controls a modulation frequency according to optical absorption characteristics of the atoms by quantum interference effects of a pair of resonance laser beams, wherein the side bands include second-order or higher-order sidebands.

First claim

The invention claimed is:

1. An atomic oscillator comprising:
an alkali-metal cell in which alkali-metal atoms are enclosed;
a light source configured to irradiate the atoms in the alkali-metal cell with laser beams;
a photodetector configured to detect a light amount of the laser beams passing through the alkali-metal cell to enter the photodetector;
a controller configured to generate a pair of laser beams with different wavelengths by performing frequency modulation of a carrier on the light source, cause the pair of laser beams with the different wavelengths to enter the alkali-metal cell, and control a modulation frequency according to optical absorption characteristics of the atoms by quantum interference effects of a pair of resonance laser beams, wherein the laser beams entering the alkali-metal cell are pulsed laser beams; and
a detector configured to detect a Ramsey interrogation signal, in a pulsed interrogation mode,
wherein the pair of laser beams with the different wavelengths are both third-order sidebands, to permit the modulation frequency for the Ramsey interrogation signal to be reduced.

2. The atomic oscillator according to claim 1 , wherein the pulsed laser beams have a waveform in a form of a square wave.

3. The atomic oscillator according to claim 1 , wherein the pulsed laser beams have a waveform in a form of a triangular wave.

4. The atomic oscillator according to claim 1 , wherein the controller is configured to generate the pulsed laser beams by modulating the laser beams emitted from the light source by using a liquid crystal element.

5. The atomic oscillator according to claim 1 , wherein the light source is made of a surface emitting laser.

6. An interrogation method of CPT resonance by an atomic oscillator including an alkali-metal cell in which alkali-metal atoms are enclosed, a light source configured to irradiate the atoms in the alkali-metal cell with laser beams, and a photodetector configured to detect a light amount of the laser beams passing through the alkali-metal cell to enter the photodetector, the interrogation method comprising:
generating a pair of laser beams with different wavelengths by performing frequency modulation of a carrier on the light source;
causing the pair of laser beams with the different wavelengths to enter the alkali-metal cell, wherein the laser beams entering the alkali-metal cell are pulsed laser beams;
detecting a Ramsey interrogation signal, in a pulsed interrogation mode; and
controlling a modulation frequency according to optical absorption characteristics of the atoms by quantum interference effects of a pair of resonance laser beams,
wherein the pair of laser beams with the different wavelengths are both third-order sidebands, to permit the modulation frequency for the Ramsey interrogation signal to be reduced.

7. The interrogation method according to claim 6 , wherein the pulsed laser beams have a waveform in a form of a square wave.

8. The interrogation method according to claim 6 , wherein the pulsed laser beams have a waveform in a form of a triangular wave.

9. The interrogation method according to claim 6 , wherein the generating includes generating the pulsed laser beams by modulating the laser beams emitted from the light source by using a liquid crystal element.

10. The interrogation method according to claim 6 , wherein the light source is made of a surface emitting laser.

Assignees

• Goka Shigeyoshi
• Yano Yuichiro
• Ricoh Co Ltd
• Univ Tokyo Metropolitan

Inventors

• Goka Shigeyoshi
• Yano Yuichiro

Classifications

• H03B17/00

  Generation of oscillations using radiation source and detector, e.g. with interposed variable obturator · CPC title

• H01S5/0687

  Stabilising the frequency of the laser · CPC title

• H03L7/26 Primary

  using energy levels of molecules, atoms, or subatomic particles as a frequency reference · CPC title

• H01S5/0085

  for modulating the output, i.e. the laser beam is modulated outside the laser cavity · CPC title

• G04F5/145

  using Coherent Population Trapping · CPC title