Off-axis cavity absorption cell
First Claim
1. An absorption cell forming a coupling aperture and comprising opposed astigmatic mirrors that define an actual closed optical path from the coupling aperture and back to it, consisting of an odd number N of cycles through the absorption cell, in which the locations of the spots at which the actual path hits one of the mirrors, as a function of those spots'"'"' order of occurrence, exhibits motion consisting essentially of only two frequency components kx /N and ky /N associated with high-frequency and low-frequency axes, respectively, along which the contribution of the other frequency component is essentially zero, where kx and ky are different integers and their common factors, other than unity, with N are distinct, each of the mirrors having principal radii rx '"'"' and ry '"'"' related to the principal radii rx and ry >
- rx of a prototype cell by the relationships rx '"'"'<
rx /(1+Δ
e) and ry '"'"'>
ry /(1-Δ
e), where Δ
e=2×
10-4, the axes of the prototype cell'"'"'s mirrors are oriented with their principal axes aligned and define a prototype closed optical path consisting of the same odd number N of cycles through the prototype cell, and the locations at which the prototype path strikes a mirror make kx cycles in the direction of one principal axis and ky cycles in the direction of the other principal axis.
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Accused Products
Abstract
An off-axis cavity absorption cell (10) includes astigmatic mirrors (22, 28). The cell design is based on a prototype design that yields a closed beam path having a desired geometry, but the mirrors are fabricated so that the ratios of their radii of curvature are actually larger than those calculated for the prototype. To achieve the desired closed beam path, the mirror spacing is adjusted from that of the prototype design, and the planes of their axes of greatest curvature are oriented out of the alignment that characterizes the prototype design. If the mirrors'"'"' manufacturing process yields errors in the curvature-radius ratios within certain prescribed limits, a cell of this design can be adjusted to achieve the closed beam path by simply changing the mirror separation and the "twist angle" between their respective planes of maximum curvature radius.
37 Citations
11 Claims
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1. An absorption cell forming a coupling aperture and comprising opposed astigmatic mirrors that define an actual closed optical path from the coupling aperture and back to it, consisting of an odd number N of cycles through the absorption cell, in which the locations of the spots at which the actual path hits one of the mirrors, as a function of those spots'"'"' order of occurrence, exhibits motion consisting essentially of only two frequency components kx /N and ky /N associated with high-frequency and low-frequency axes, respectively, along which the contribution of the other frequency component is essentially zero, where kx and ky are different integers and their common factors, other than unity, with N are distinct, each of the mirrors having principal radii rx '"'"' and ry '"'"' related to the principal radii rx and ry >
- rx of a prototype cell by the relationships rx '"'"'<
rx /(1+Δ
e) and ry '"'"'>
ry /(1-Δ
e), where Δ
e=2×
10-4, the axes of the prototype cell'"'"'s mirrors are oriented with their principal axes aligned and define a prototype closed optical path consisting of the same odd number N of cycles through the prototype cell, and the locations at which the prototype path strikes a mirror make kx cycles in the direction of one principal axis and ky cycles in the direction of the other principal axis. - View Dependent Claims (2, 3, 4)
- rx of a prototype cell by the relationships rx '"'"'<
- 5. An absorption cell forming a coupling aperture and comprising opposed astigmatic mirrors forming a twist angle of more than 1.0 degree with respect to each other and defining, for light entering the coupling aperture at a predetermined angle, a closed multiple-reflection path from the inlet aperture and back to it.
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8. A method of constructing an absorption cell comprising the steps of:
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A) constructing a cell that forms a coupling aperture and includes opposed astigmatic mirrors spaced apart along a central axis therethrough; and B) varying the mirrors'"'"' twist angle and their separation along the central axis until, at a twist angle that exceeds 1.0 degree, the mirrors define, for light entering the inlet aperture at a predetermined angle, a closed multiple-reflection path from the coupling inlet aperture and back. - View Dependent Claims (9, 10, 11)
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Specification