Monolithic element and system for collimating or focusing laser light from or to an optical fiber
A monolithic optical element and system is used for collimating or focusing laser light from or to optical fibers. The optical fiber terminates in a tip that directly abuts against the first surface of the optical element. The optical element may provide a collimation or focusing function depending upon whether the abutting fiber delivers light for collimation or receives focused light from a collimated beam. The optical element may be a standard or modified barrel or drum lens, with the first and second surfaces being convex curved surfaces having the same or different radii of curvature. The end of the optical element to which the fiber abuts may have a diameter to match the inner diameter of a ferrule for positioning the fiber. A pair of the elements may be used for collimation and focusing in a Raman probehead or other optical detection system.
1. An optical measurement probe configured for interconnection to a first optical fiber for carrying excitation energy to the probe and to a second optical fiber for carrying collected energy from the probe for analysis, the probe comprising:
a first monolithic optical component including a first cylindrical portion with a first incident surface for receiving light from an end of the first optical fiber and a second cylindrical portion with a first transmission surface outputting an expanded, collimated excitation beam for direction to a sample, wherein the first cylindrical portion has a diameter that is smaller than that of the second cylindrical portion, and wherein the first optical component further includes a first stepped transition region between the first cylindrical portion and the second cylindrical portion;
a beam combiner for merging a collimated collection beam from the sample with the collimated excitation beam to produce a counter-propagating combined beam; and
a second monolithic optical component including a third cylindrical portion with a second incident surface for receiving the combined beam and a fourth cylindrical portion with a second transmission surface structured to output a focused beam into an end of the second optical fiber, wherein the fourth cylindrical portion has a diameter that is smaller than that of the third cylindrical portion, and wherein the second optical component further includes a second stepped transition region between the third cylindrical portion and the fourth cylindrical portion, and
wherein the end of the first optical fiber directly contacts the first incident surface of the first optical component and the end of the second optical fiber directly contacts the second transmission surface of the second optical component.
2. The optical probehead of claim 1 , wherein the first optical component and the second optical component are modified barrel or drum lenses.
3. The optical probe of claim 1 , wherein the first optical component and the second optical component are identical lenses.
4. The optical probe of claim 1 , wherein the diameters of the first cylindrical portion and the fourth cylindrical portion are sized to complement the inner diameter of a ferrule receiving each respective optical fiber.
5. The optical probe of claim 1 , wherein the excitation beam and the collection beam are respectively configured to induce and collect Raman scattering from the sample.
6. The optical probe of claim 1 , wherein the first incident surface and the first transmission surface of the first optical component are convex curved surfaces, and/or the second incident surface and the second transmission surface of the second optical component are convex curved surfaces.
7. The optical probe of claim 6 , wherein the first incident surface and the first transmission surface of the first optical component have the same radius of curvature, and/or the second incident surface and the second transmission surface of the second optical component have the same radius of curvature.
8. The optical probe of claim 6 , wherein a radius of curvature of the first incident surface of the first optical component is larger than a radius of curvature of the first transmission surface of the first optical component.
9. The optical probe of claim 6 , wherein a radius of curvature of the second incident surface of the second optical component is larger than a radius of curvature of the second transmission surface of the second optical component.
10. The optical probe of claim 1 , wherein a diameter and a radius of curvature of the first transmission surface, a length, and a refractive index of the first optical component are selected in combination to produce exact collimation from a point on the center of a tip of the first optical fiber, and
wherein a diameter and a radius of curvature of the second incident surface, a length, and a refractive index of the second optical component are selected in combination to produce exact focusing to a point on the center of a tip of the second optical fiber.
11. The optical probe of claim 10 , wherein the refractive indices the first optical component and the second optical component are sufficiently high to minimize spherical aberration.
12. The optical probe of claim 1 , wherein the first transmission surface of the first optical component and the second incident surface of the second optical component are aspheric.
13. The optical probe of claim 1 , wherein the first optical component and the second optical component each forms a gradient index lens.
14. The optical probe of claim 1 , wherein the probe is employed in a Raman measurement probe.
15. The optical probe of claim 1 , wherein the stepped transition regions of the first optical component and the second optical component each include relief regions.
16. The optical probe of claim 15 , wherein the relief regions each are embodied to facilitate a mating connection between the first optical component and a ferrule of the first optical fiber and between the second optical component and a ferrule of the second optical fiber.