LASER SPECTROSCOPIC SENSOR USING ORBITAL ANGULAR MOMENTUM

• US 20160109361A1
• Filed: 09/01/2015
• Published: 04/21/2016
• Est. Priority Date: 10/16/2014
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Laboratories America Inc (NEC Corporation)
• Inventors: Wang, Ting, Weng, Yi
• Granted Patent: US 9,784,673 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01N 21/21 Polarisation-affecting properties G01N21/19 takes precedence
• CPC Class Codes: G01N 21/27 using photo-electric detection G01N21/31 takes precedence; circuits for computing concentration logarithmic circuits G06G7/24; photometric circuits in general G01J
• CPC Class Codes: G01N 21/3504 for analysing gases, e.g. multi-gas analysis
• CPC Class Codes: G01N 2201/06113 Coherent sources; lasers

Abstract

A method and system for optical angular momentum (OAM) spectroscopy includes generating a beam of light having a single OAM mode. A first spectrum of the beam of light is detected and the beam of light is passed through a gas to attenuate the beam of light in accordance with a presence and concentration of a respective gas. A second spectrum the beam of light is coherently detected and a difference between the first and second spectrum for the beam of light is analyzed to determine the presence and concentration of the respective gas.

Claims

1. A method for optical angular momentum (OAM) spectroscopy, comprising:

generating a beam of light having a single OAM mode;

detecting a first spectrum of the beam of light;

passing the beam of light through a gas to attenuate the beam of light in accordance with a presence and concentration of a respective gas;

coherently detecting a second spectrum the beam of light; and

analyzing a difference between the first and second spectrum for the beam of light to determine the presence and concentration of the respective gas.

2. The method of claim 1, further comprising generating a plurality of beams of light, each beam having a different OAM mode and a different respective gas.

3. The method of claim 2, wherein generating the plurality of beams of light comprises splitting a laser beam into the plurality of beams and imposing a respective OAM mode on each of the plurality of beams.

4. The method of claim 3, wherein the laser beam has a wavelength in the middle infrared range.

5. The method of claim 3, wherein imposing an OAM mode on a beam of light comprises passing the beam through a phase plate.

6. The method of claim 3, wherein imposing an OAM mode on a beam of light comprises passing the beam through a hologram plate.

7. The method of claim 1, wherein analyzing the difference between the first and second spectrum comprises matching the difference to an expected spectrum for the respective gas.

8. The method of claim 1, further comprising splitting the beam of light into orthogonal polarizations before the beam passes through the gas.

9. The method of claim 8, wherein coherently detecting the second spectrum comprises independently detecting each of the orthogonal polarizations.

10. An optical angular momentum (OAM) spectroscopy sensor, comprising:

a laser;

an OAM converter configured to impose an OAM mode on an output of the laser and produce an OAM beam;

a first OAM receiver configured to detect a first spectrum of the OAM beam from the OAM converter;

a gas cavity containing a mixture comprising one or more component gases configured to attenuate the OAM beam in accordance with a presence and concentration of a respective gas;

a second OAM receiver configured to coherently detect a second spectrum of the OAM beam after the OAM beam has passed through the gas cavity; and

a processor configured to analyze a difference between the first and second spectrum for the beam of light to determine the presence and concentration of the respective gas.

11. The sensor of claim 10, wherein the OAM converter comprises a splitter configured to split the output of the laser into a plurality of beams and is further configured to impose a respective OAM mode on each of the plurality of beams.

12. The sensor of claim 11, wherein the laser output has a wavelength in the middle infrared range.

13. The sensor of claim 11, wherein the OAM converter comprises a phase plate to impose an OAM mode on a beam.

14. The sensor of claim 11, wherein the OAM converter comprises a hologram plate to impose an OAM mode on a beam.

15. The sensor of claim 10, wherein the processor is further configured to match the difference to an expected spectrum for the respective gas.

16. The sensor of claim 10, further comprising a polarizing splitter configured to split the OAM beam into orthogonal polarizations before the beam passes through the gas cavity.

17. The sensor of claim 16, wherein the second OAM receiver is configured to independently detect each of the orthogonal polarizations.