This paper presents a maskless micromachining process that can reform or reshape a section of an optical fiber into a complex 3-D photonic microstructure. This proposed micromachining process is based on the etching rate control achieved by the introduction of phosphorus pentoxide into silica glass through standard fiber manufacturing technology. Regions within a fiber cross section doped with phosphorus pentoxide can etch up to 100 times faster than pure silica when exposed to hydrofluoric acid. Various new photonic devices can be effectively and economically created by design and production of purposely doped fibers that are spliced at the tip or in-between standard lead-in fibers, followed by etching into a final structure
https://ieeexplore.ieee.org/document/5873110?arnumber=5873110&tag=1
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