초록 ▼

A double-pass fiber-optic based spectroscopic gas sensor delivers Raman excitation light and infrared light to a hollow structure, such as a hollow fiber waveguide, that contains a gas sample of interest. A retro-reflector is placed at the end of this hollow structure to send the light back through

A double-pass fiber-optic based spectroscopic gas sensor delivers Raman excitation light and infrared light to a hollow structure, such as a hollow fiber waveguide, that contains a gas sample of interest. A retro-reflector is placed at the end of this hollow structure to send the light back through the waveguide where the light is detected at the same end as the light source. This double pass retro reflector design increases the interaction path length of the light and the gas sample, and also reduces the form factor of the hollow structure.

대표청구항 ▼

1. An apparatus, comprising: a hollow gas sampling structure having a first end, a second end, a diameter ranging from at least 200 micrometers to no more than 3 millimeters, a reflector located at said second end, an opening configured wherein a gas can freely but not forcibly migrate into and out

1. An apparatus, comprising: a hollow gas sampling structure having a first end, a second end, a diameter ranging from at least 200 micrometers to no more than 3 millimeters, a reflector located at said second end, an opening configured wherein a gas can freely but not forcibly migrate into and out of said structure and a reflective inner wall comprising a reflective material selected from the group consisting of a metal and a dielectric, wherein said reflective material is reflective and not absorbing of (i) Raman excitation light and Raman light having a wavelength within a range from UV to visible and (ii) infrared (IR) radiation having a wavelength within a range from 3 μm to 20 μm;a fiber optic bundle comprising a first distal end operatively and proximately connected to said first end, wherein said fiber optic bundle further comprises:a multimode first fiber optic configured for transmitting said Raman excitation light into said gas to produce Raman light generated in said gas, wherein said first fiber optic comprises a first fiber optic proximal end and a first fiber optic distal end, wherein said first fiber optic distal end terminates at said first distal end;a multimode second fiber optic configured for transmitting said IR radiation into said gas to produce attenuated IR radiation, wherein said second fiber optic comprises a second fiber optic proximal end and a second fiber optic distal end, wherein said second fiber optic distal end terminates at said first distal end, wherein said second fiber optic is further configured for collecting said attenuated IR radiation;a multimode first collection fiber configured for collecting said Raman light, wherein said first collection fiber optic comprises a first collection fiber optic proximal end and a first collection fiber optic distal end, wherein said first collection fiber optic distal end terminates at said first distal end;a first source of said Raman excitation light, wherein said first source is configured to direct said Raman excitation light into said first fiber optic proximal end;a second source of said IR radiation, wherein said second source is configured to direct said IR radiation into said second fiber optic proximal end;a Raman light detector configured to receive said Raman light from said first collection fiber optic proximal end; andan IR radiation detector configured to receive said attenuated IR radiation. 2. The apparatus of claim 1, wherein said IR radiation detector is configured to receive said attenuated IR radiation from said second fiber optic proximal end. 3. The apparatus of claim 1, wherein said bundle further comprises as multimode second collection fiber configured for collecting said attenuated IR radiation, wherein said second collection fiber optic comprises a second collection fiber optic proximal end and a second collection fiber optic distal end, wherein said second collection fiber optic distal end terminates in proximity with said first distal end, and wherein said IR radiation detector is configured to receive said attenuated IR radiation from said second collection fiber optic proximal end. 4. The apparatus of claim 1, further comprising a lens located such that said Raman excitation light and said IR radiation exiting said first distal end must propagate through said lens before interacting with gas located within said hollow gas sampling structure. 5. The apparatus of claim 1, further comprising a non-holographic filter located such that said Raman excitation light and said IR radiation exiting said first distal end must propagate through said filter before interacting with gas located within said hollow as sampling structure. 6. The apparatus of claim 1, wherein said mirror comprises a retroreflector. 7. The apparatus of claim 1, wherein said hollow gas sampling structure comprises a geometry selected from the group consisting of a tube and a groove in a planar waveguide. 8. The apparatus of claim 1, wherein said metal is selected from the group consisting of silver, gold, aluminum, platinum and rhodium and wherein said dielectric is configured within one or more layers of reflective and refractive coatings. 9. The apparatus of claim 1, wherein the inner surface of said hollow gas sampling structure comprises a feature selected from the group consisting of a roughened surface and nanostructures. 10. A method, comprising: providing the apparatus of claim 1;directing said Raman excitation light into said first fiber optic proximal end such that it propagates through said multimode first fiber optic to exit said first fiber optic distal end and enter said hollow gas sampling structure to interact with said gas and produce said Raman light;collecting said Raman light into said first collection fiber optic distal end such that it propagates through said first multimode collection fiber and exits said first collection fiber optic proximal end;detecting said Raman light that exits from said first collection fiber optic proximal end;directing said IR radiation into said second fiber optic proximal end Such that it propagates through said multimode second fiber optic to exit said second fiber optic distal end and enter said hollow gas sampling structure to interact with said gas to produce said attenuated IR radiation; anddetecting said attenuated IR radiation. 11. The method of claim 10, wherein the step of detecting said attenuated IR radiation comprises receiving into an IR radiation detector said attenuated IR radiation that exits from said second fiber optic proximal end. 12. The method of claim 10, wherein said apparatus further comprises a multimode second collection fiber configured for collecting said attenuated IR radiation, wherein said second collection fiber optic comprises a second collection fiber optic proximal end and a second collection fiber optic distal end, wherein said second collection fiber optic distal end terminates in proximity with said first distal end, wherein the step of detecting said attenuated IR radiation comprising receiving into an IR radiation detector said attenuated IR radiation that exits from said second collection fiber optic proximal end. 13. The method of claim 10, wherein said apparatus further comprises a lens located between said first distal end and said gas. 14. The Method of claim 10, wherein said apparatus further comprises a filter located between said first distal end and said gas. 15. The method of claim 10, wherein said mirror comprises a retroreflector. 16. The method of claim 10, wherein said hollow gas sampling structure comprises a geometry selected from the group consisting of a tube and a groove in a planar waveguide. 17. The method of claim 10, wherein said metal is selected from the group consisting of silver, gold, aluminum, platinum and rhodium and wherein said dielectric is configured within one or more layers of reflective and refractive coatings. 18. The method of claim 10, wherein the inner surface of said hollow gas sampling structure comprises a feature selected from the group consisting of a roughened surface and nanostructures. 19. The method of claim 10, further comprising analyzing at least one of said Raman light and said attenuated IR radiation to determine at least a portion of the composition of said gas sample. 20. The Method of claim 10, further comprising reflecting from said reflector at least a portion of one of said Raman excitation light and said IR radiation.