Laser spectroscopic sensor using orbital angular momentum
View Patent ↗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.
1. A method for optical angular momentum (OAM) spectroscopy, comprising:
generating a plurality of beams of light, each beam having a different respective OAM mode, by splitting a laser beam and imposing a respective OAM mode onto each of the split beams;
detecting a first absorption spectrum of each of the beams of light;
passing the beams of light through a gas at the same time to attenuate the beams of light in accordance with a presence and concentration of a respective gas after detecting the first absorption spectra;
coherently detecting a second absorption spectrum of each of the beams of light; and
analyzing a difference between the first and second absorption spectra for the beams of light to determine the presence and concentration of the respective gas.
2. The method of claim 1 , wherein the laser beam has a wavelength in the middle infrared range.
3. The method of claim 1 , wherein imposing an OAM mode on a beam of light comprises passing the beam through a phase plate.
4. The method of claim 1 , wherein imposing an OAM mode on a beam of light comprises passing the beam through a hologram plate.
5. 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.
6. The method of claim 1 , further comprising splitting the beam of light into orthogonal polarizations before the beam passes through the gas.
7. The method of claim 6 , wherein coherently detecting the second spectrum comprises independently detecting each of the orthogonal polarizations.
8. An optical angular momentum (OAM) spectroscopy sensor, comprising:
a laser configured to output a plurality of unconverted beams;
an OAM converter configured to impose a respective OAM mode on each of the unconverted beams to produce respective OAM beams;
a first OAM receiver configured to detect a first absorption spectrum of each of the OAM beams from the OAM converter;
a gas cavity containing a mixture comprising one or more component gases configured to attenuate each of the OAM beams at the same time in accordance with a presence and concentration of a respective gas;
a second OAM receiver configured to coherently detect a second absorption spectrum of each of the OAM beams after the OAM beams have passed through the gas cavity; and
a processor configured to analyze a difference between the first and second absorption spectra for the beams of light to determine the presence and concentration of the respective gas.
9. The sensor of claim 8 , wherein the laser output has a wavelength in the middle infrared range.
10. The sensor of claim 8 , wherein the OAM converter comprises a phase plate to impose an OAM mode on a beam.
11. The sensor of claim 8 , wherein the OAM converter comprises a hologram plate to impose an OAM mode on a beam.
12. The sensor of claim 8 , wherein the processor is further configured to match the difference to an expected spectrum for the respective gas.
13. The sensor of claim 8 , further comprising a polarizing splitter configured to split the OAM beam into orthogonal polarizations before the beam passes through the gas cavity.
14. The sensor of claim 13 , wherein the second OAM receiver is configured to independently detect each of the orthogonal polarizations.