Optical multi-pass cell

1. An optical multi-pass cell ( 100 ), comprising:

a housing ( 101 ) defining a sample cavity ( 109 ) for receiving a sample under test;

first and second end mirrors ( 103 , 104 ) positioned within the housing ( 101 ), separated by a distance, L, and facing one another coaxially to an optical axis ( 113 ) extending between the first and second end mirrors ( 103 , 104 ), the first and second mirrors ( 103 , 104 ) being configured to reflect a beam of light directed at one of the first or second end mirrors ( 103 , 104 ) off-axis from the optical axis ( 113 ) one or more times between the first and second end minors ( 103 , 104 ) through the sample cavity ( 109 ) at a first distance from the optical axis ( 113 ) to create a first beam pattern ( 330 ); and

one or more relay mirrors ( 220 ) positioned to intercept the beam of light and configured to reflect the beam of light such that at least a second beam pattern ( 331 ) is created between the first and second end mirrors ( 103 , 104 ) at a distance from the optical axis ( 113 ) different from the first distance of the first beam pattern ( 330 ) such that the second beam pattern ( 331 ) does not overlap the first beam pattern ( 330 ).

2. The optical multi-pass cell ( 100 ) of claim 1 , further comprising an aperture ( 116 ) formed in one of the first or second end mirrors ( 103 , 104 ), wherein a relay mirror ( 220 ) of the one or more relay minors ( 220 ) is positioned within the aperture ( 116 ).

3. The optical multi-pass cell ( 100 ) of claim 1 , further comprising first and second end caps ( 105 , 106 ) coupled to the housing ( 101 ).

4. The optical multi-pass cell ( 100 ) of claim 3 , further comprising an optical aperture ( 107 ) formed in the first end cap ( 105 ) and aligned with an aperture ( 115 ) formed in the first end mirror ( 103 ) for introducing the beam of light into the sample cavity ( 109 ) and/or extracting the beam of light out of the sample cavity ( 109 ).

5. The optical multi-pass cell ( 100 ) of claim 3 , further comprising a first sample aperture ( 108 ) formed in the first end cap ( 105 ) and a second sample aperture ( 208 ) formed in the second end cap ( 106 ).

6. The optical multi-pass cell ( 100 ) of claim 1 , further comprising a center rod ( 102 ) extending within the housing ( 101 ) and coupled to the first and second end mirrors ( 103 , 104 ).

7. The optical multi-pass cell ( 100 ) of claim 6 , further comprising one or more apertures ( 110 ) formed in the center rod ( 102 ) proximate the first end mirror ( 103 ).

8. The optical multi-pass cell ( 100 ) of claim 6 , further comprising one or more apertures ( 111 ) formed in the center rod ( 102 ) proximate the second end mirror ( 104 ).

9. An optical multi-pass cell ( 100 ), comprising:

a housing ( 101 ) defining a sample cavity ( 109 ) for receiving a sample under test;

first and second end mirrors ( 103 , 104 ) positioned within the housing ( 101 ), separated by a distance, L, and facing one another coaxially to an optical axis ( 113 ) extending between the first and second end mirrors ( 103 , 104 ), the first and second mirrors ( 103 , 104 ) being configured to reflect a beam of light directed at one of the first or second end mirrors ( 103 , 104 ) off-axis from the optical axis ( 113 ) one or more times between the first and second end mirrors ( 103 , 104 ) through the sample cavity ( 109 ) at a first distance from the optical axis ( 113 ) to create a first beam pattern ( 330 );

one or more relay mirrors ( 220 ) positioned to intercept the beam of light and configured to reflect the beam of light such that at least a second beam pattern ( 331 ) is created between the first and second end mirrors ( 103 , 104 ) at a distance from the optical axis ( 113 ) different from the first distance of the first beam pattern ( 330 );

a center rod ( 102 ) extending within the housing ( 101 ) and coupled to the first and second end mirrors ( 103 , 104 );

an internal cavity ( 450 ) and an optically transparent portion ( 451 ) formed in the center rod ( 102 );

an optical source ( 230 ) and an optical detector ( 231 ) located in the internal cavity ( 450 );

one or more redirecting mirrors ( 460 a , 460 c ) located in the internal cavity ( 450 ); and

one or more redirecting mirrors ( 460 b ) located in the sample cavity ( 109 ), the redirecting mirrors ( 460 a - 460 c ) being configured to reflect a beam of light from the optical source ( 230 ) towards one of the first or second end mirrors ( 103 , 104 ) and reflect the beam of light from one of the first or second end mirrors ( 103 , 104 ) towards the optical detector ( 231 ).

10. A method for forming an optical multi-pass cell including a housing defining a sample cavity, comprising steps of:

positioning a first end mirror within the housing at a first end;

positioning a second end mirror within the housing at a second end, such that the first and second end mirrors are separated by a distance and face one another coaxial to an optical axis that extends between the first and second end mirrors and wherein the first and second end mirrors are configured to reflect a beam of light directed at one of the first or second end mirrors off-axis from the optical axis one or more times between the first and second end mirrors through the sample cavity at a first distance from the optical axis to create a first beam pattern; and

positioning one or more relay mirrors to intercept the beam of light and reflect the beam of light such that at least a second beam pattern is created between the first and second end mirrors at a distance from the optical axis different from the first distance of the first beam pattern such that the second beam pattern does not overlap the first beam pattern.

11. The method of claim 10 , further comprising steps of:

forming an aperture in one of the first or second end mirrors; and

positioning a relay mirror of the one or more relay mirrors within the aperture.

12. The method of claim 10 , further comprising a step of coupling first and second end caps to the housing.

13. The method of claim 12 , further comprising steps of:

forming an optical aperture in the first end cap; and

forming an aperture in the first end mirror to align with the optical aperture.

14. The method of claim 12 , further comprising steps of:

forming a first sample aperture in the first end cap; and

forming a second sample aperture in the second end cap.

15. The method of claim 10 , further comprising a step of extending a center rod within the housing.

16. The method of claim 15 , further comprising a step of forming one or more apertures in the center rod proximate the first end mirror.

17. The method of claim 15 , further comprising a step of forming one or more apertures in the center rod proximate the second end mirror.

18. A method for forming an optical multi-pass cell including a housing defining a sample cavity, comprising steps of:

positioning a first end mirror within housing at a first end;

positioning a second end mirror within the housing at a second end, such that the first and second end mirrors are separated by a distance and face one another coaxial to an optical axis that extends between the first and second end mirrors and wherein the first and second end mirrors are configured to reflect a beam of light directed at one of the first or second end mirrors off-axis from the optical axis one or more times between the first and second end mirrors through the sample cavity at a first distance from the optical axis to create a first beam pattern;

positioning one or more relay mirrors to intercept the beam of light and reflect the beam of light such that at least second beam pattern is created between the first and second end mirrors at a distance from the optical axis different from the first distance of the first bean pattern;

extending a center rod within the housing;

forming an internal cavity and an optically transparent portion in the center rod;

positioning an optical source and an optical detector in the internal cavity;

positioning one or more redirecting mirrors in the internal cavity; and

positioning one more redirecting mirrors in the sample cavity,

wherein the redirecting mirrors are configured to reflect a beam of light from the optical source towards one of the first or second end minors and reflect the beam of light from one of the first or second end mirrors towards the optical detector.