Microsphere based patterning of metal optic/plasmonic sensors including fiber based sensors

A method of forming a network array of nanoantennas on an optical fiber, wherein the optical fiber comprises a glass fiber and an encapsulation of the glass fiber, wherein the glass fiber comprises a core and a cladding, the method comprising:

• conducting microsphere photolithography on an optical fiber assembly, wherein the optical fiber assembly comprises:
• an exposed area of the glass fiber that is an end surface of the glass fiber and/or a portion of the circumferential surface of the glass fiber from which a portion of the encapsulation has been removed from the optical fiber;
• an optional sub-photoresist layer on the exposed area of the glass fiber, wherein the optional sub-photoresist layer has a thickness in a range of about 25 nm to about 150 nm, wherein the sub-photoresist layer comprises a metal, dielectric, semiconductor, or combination thereof;
• a photoresist layer secured, directly or indirectly via the optional sub-photoresist layer, to the exposed area of the glass fiber, wherein the photoresist layer comprises a negative photoresist composition or a positive photoresist composition;
• and
• a layer of microspheres, wherein the microspheres are transparent to the photolithographic radiation and have a nominal diameter in a range of about 500 nm to about 3 μm and are in a hexagonal closed packed configuration, and wherein the microspheres in substantially uniform contact with the photoresist layer;
• wherein the microsphere photolithography comprises:
• directing the photolithographic radiation toward the microsphere layer at an incidence having an polar angle (θ) that is in a range of about −30° to about 30° and an azimuthal angle (φ) that is in a range of 0° to 360° for an exposure dosage that is in a range of about 0.1 mJ/cm2 to about 25 mJ/cm2 such that the microspheres focus the incident photolithographic radiation to produce an array of photonic jets that expose portions of the photoresist layer, wherein the exposed portions have:
• locations that depend, at least in part, on the incidence;
• diameters (d) that depend, at least in part, on the exposure dosage, wherein d is in a range of about 50 nm to about 750 nm;
• a thicknesses of the photoresist layer;
• and
• a periodicity that depends, at least in part, on the nominal diameter of the microspheres and the incidence, wherein the periodicity is in a range of about 0.5 μm to about 3 μm;
• wherein the exposed portions form a repeating pattern of a 2-D shape at the surface of the photoresist layer;
• developing the exposed photoresist layer to remove the exposed portions, in the case of a positive photoresist composition, or the unexposed portions, in the case of a negative photoresist composition;
• forming the nanoantennas on the portion of the exposed area of the glass fiber, if the optional sub-photoresist layer is not present, or the optional sub-photoresist layer, if present, in a pattern corresponding to the removed portions of the developed photoresist layer, wherein said forming of the nanoantennas is accomplished via etching of the optional sub-photoresist layer, if present, or depositing a nanoantenna material that comprises a comprises a metal, dielectric, semiconductor, or combination;
• and
• removing the remaining photoresist to expose the nanoantennas;
• thereby forming the network array of nanoantennas on the optical fiber.