Fabrication of corrugated probes for scanning near-field optical microscopy

We present a method of fabricating aperture tapered-fiber metal-coated SNOM probes with a corrugated core surface which assures efficient photon-to-plasmon conversion and thus high energy throughput. High energy throughput allows for a small apex aperture and high resolution. The procedure consists of recording of Bragg grating in the to-be-tapered part of a Ge-doped silica fiber and chemical etching with the Turner method. Bragg gratings are recorded with UV light through nearly sinusoidal phase masks of chosen lattice constants. The refractive index contrast in the Bragg grating differentiates the etch rate of the Ge-doped hydrogenated fiber core in exposed and unexposed parts by about 100 nm/min at room temperature.