High pressure CVD inside microstructured optical fibres

Abstract

We report the fabrication of semiconductor structures within holey fibres via a pressure driven microfluidic chemical vapour deposition process, demonstrating templated growth of crystalline Group IV semiconductor structures and devices in extreme aspect ratio geometries.

High‐Pressure Chemical Deposition for Void‐Free Filling of Extreme Aspect Ratio Templates

“…[ 20 ] For such applications in-fi ber wires can be confi gured as centimeters long void-free coaxial junction devices by sequentially depositing layers of doped semiconductor. [ 4 ] This "outside in" approach to coaxial junction fabrication in microstructured optical fi ber templates, in contrast to an "inside out" approach such as deposition on the exterior of nanowires, has the advantage of avoiding surface roughness associated with the deposition. [ 21 ] Densely packed arrays of these junctions can be precisely patterned by appropriate choice of the microstructured optical fi ber template.…”

“…[ 4 ] Just like silica fi bers, these pores can have exceptional diameter uniformity along their length, a circular cross-section, and surface roughness approaching atomically smooth ( ∼ 0.1 nm root mean square (RMS)). [ 5 ] CFD in microstructured optical fi bers is practical and low cost and can be confi gured for large scale parallel production.…”

Hybrid Optical Fibers – An Innovative Platform for In‐Fiber Photonic Devices

“…In this process, the holes of microstructured silica fi bers act as chemical microreactors, in which the materials are deposited from the gas phase on the inner side walls. [ 60 ] The various gaseous ingredients needed for the process are inserted via high external pressure (of the order of several hundreds of bars), and the actual chemical reactions are either thermally stimulated or externally triggered via photoexcitation (e.g., by side focusing laser light onto the capillary). [ 61 ] The deposition process starts at the side walls of the bore, with the fi nal fi lm thickness being determined by the deposition time up to the point when the bore is completely fi lled.…”

“…This technique was shown to be capable of producing semiconductor wires with diameters of the order of several micrometers down to hundreds of nanometers of various materials of extremely good optical and electrical quality. [ 60 ] By controlling the fabrication process and applying particular post-processing techniques, [ 62 ] the morphologies of the incorporated materials can be engineered, allowing the production of entirely amorphous, [ 63 ] polycrystalline [ 64 ] or even single-crystal semiconductor [ 61 ] wires inside MOFs. In addition to their optical functionalities, these structures allow the integration of semiconductor junctions directly into fi bers, which makes them very attractive from the optoelectronic perspective.…”

Simultaneous tapering and crystallisation of silicon core optical fibres

“…A high-pressure microfluidic chemical deposition technique, as described in [1], was used to fabricate the silicon optical fibre. The fibre consisted of an amorphous silicon core, with a diameter of 2.5 µm, and a silica cladding, with a diameter of 125 µm.…”