Mode matching for cavity ring-down spectroscopy based upon Brewster's angle prism retroreflectors
First Claim
1. A resonator for a ring-down cavity spectroscopy cell having an optic axis, the resonator comprising:
- a first Brewster'"'"'s angle retroreflector prism having a plurality of total internal reflection surfaces with one of the total internal reflection surfaces being a curved surface;
a second Brewster'"'"'s angle retroreflector prism having a plurality of total internal reflection surfaces and being disposed in alignment with the first prism along the optic axis of the resonator; and
an optical element for coupling radiation into one of the first and second prisms.
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Accused Products
Abstract
A stable resonator for a ring-down cavity spectroscopy cell having an optic axis. The resonator includes two Brewster'"'"'s angle retroreflector prisms, each having a plurality of total internal reflection surfaces, with one of the total internal reflection surfaces of at least one of the prisms having a curved surface (either a ground curved surface or a surface curved by the addition, through optically contacting or gluing, of a plano-convex lens to the surface). The prisms are disposed in alignment along the optic axis of the resonator. A spherical mirror or lens, tilted from normal incidence to produce a desired degree of astigmatism, mode matches the radiation into the resonator. One or both of the prisms can be rotated so that light rays enter and leave a surface of the prism nearly at Brewster'"'"'s angle to the normal of the prism surface. This feature maintains alignment between the prisms and allows the resonator to be tuned.
39 Citations
22 Claims
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1. A resonator for a ring-down cavity spectroscopy cell having an optic axis, the resonator comprising:
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a first Brewster'"'"'s angle retroreflector prism having a plurality of total internal reflection surfaces with one of the total internal reflection surfaces being a curved surface;
a second Brewster'"'"'s angle retroreflector prism having a plurality of total internal reflection surfaces and being disposed in alignment with the first prism along the optic axis of the resonator; and
an optical element for coupling radiation into one of the first and second prisms. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
wherein a distance between the entry point and the waist point is approximately equal to a distance between the entry point and the effective waist point. -
12. The resonator as recited in claim 11, wherein the distance between the entry point and the waist point is an optical distance, the optical distance equal to a physical distance between the entry point and the waist point multiplied by an index of refraction of the second Brewster'"'"'s angle retroreflector prism.
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13. A resonator for a ring-down cavity spectroscopy cell having an optic axis, the resonator comprising:
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a first Brewster'"'"'s angle retroreflector prism having;
(a) a plurality of total internal reflection surfaces with one of the total internal reflection surfaces being a curved surface, (b) an apex angle of about 135°
minus Brewster'"'"'s angle,(c) a second angle of about 90°
, and(d) a third angle of about 180°
minus two times Brewster'"'"'s angle;
a second Brewster'"'"'s angle retroreflector prism having a plurality of total internal reflection surfaces and being disposed in alignment with the first prism along the optic axis of the resonator; and
means for coupling radiation into one of the first and second prisms. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22)
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Specification