Nanoscale structures on optical fiber for surface enhanced Raman scattering and methods related thereto
A nanoscale structure fabricated on a planar end facet of an optic fiber is described, to enable detection of molecules by surface-enhanced Raman scattering. The nanoscale structure may comprise an array of nanopillars. The nanoscale structure may also comprise a non periodic, or random, surface-relief structure. The nanoscale structure may be coated in a metal, comprising, for example, silver, gold, aluminum, iridium, platinum, palladium, copper, or a combination of the same. The nanoscale structure may be fabricated on a planar end facet of an optical fiber by interference lithography.
1. A method comprising:
providing an optical fiber having a planar facet end;
attaching a ferrule to the optical fiber adjacent to the planar facet end;
fitting the optical fiber with the ferrule on a spin coater;
coating the planar facet end of the optical fiber with the ferrule with a photoresist;
producing a pattern in the photoresist for a nanoscale structure by interference lithography;
developing the photoresist;
removing the photoresist and a portion of the optic fiber unprotected by the photoresist, thus obtaining a nanoscale structure in the optic fiber; and
depositing a layer of metal on the nanoscale structure.
2. The method of claim 1 , wherein the nanoscale structure is a periodic surface-relief structure.
3. The method of claim 1 , wherein the nanoscale structure is a non periodic surface-relief pattern.
4. The method of claim 1 , wherein the nanoscale structure is a random surface-relief pattern.
5. The method of claims 2 , wherein the relief pattern is configured to be antireflective.
6. The method of claim 1 , wherein the nanoscale structure is an array of nanopillars on the planar facet end of the optical fiber, the array of nanopillars substantially perpendicular to the planar facet end.
7. The method of claim 6 , wherein the nanopillars have a substantially cylindrical shape.
8. The method of claim 6 , wherein the nanopillars have a substantially conical shape.
9. The method of claim 1 , wherein a planar antireflective material is coated onto the facet of the optical fiber attached to the ferrule, prior to coating the photoresist, and the antireflective coating is removed during the step which removes the photoresist and a portion of the optic fiber.
10. The method of claim 1 , wherein the removal process comprises ion milling or deep reactive ion etching or inductively coupled plasma etching or electron cyclotron resonance etching.
11. The method of claim 1 , wherein the metal layer is deposited by e-beam or sputtering or thermal evaporation or chemical vapor deposition.
12. The method of claim 1 , wherein the metal layer is selected from the group consisting of: silver, gold, aluminum, iridium, platinum, palladium and copper.
13. The method of claim 1 , wherein the metal layer covers also the surface of the optic fiber between the nanopillars.
14. The method of claim 1 , wherein the metal layer coverage is non-continuous.