Extreme electronic bandgap modification in laser-crystallized silicon optical fibres

• Published in: Nature materials Vol. 13; no. 12; pp. 1122 - 1127
• Main Authors: Healy, Noel, Mailis, Sakellaris, Bulgakova, Nadezhda M., Sazio, Pier J. A., Day, Todd D., Sparks, Justin R., Cheng, Hiu Y., Badding, John V., Peacock, Anna C.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.12.2014; Nature Publishing Group
• Subjects: 140/133; 639/301/119/1000; Anisotropy; Biomaterials; Cladding; Condensed Matter Physics; Crystallization; Electronics; Fiber technology; Laser processing; Materials Science; Microelectronics; Nanotechnology; Optical and Electronic Materials; Optical properties; Photonics; Reduction; Semiconductor materials; Silica; Silicon; Telecommunications; Wavelengths
• ISSN: 1476-1122; 1476-4660
• DOI: 10.1038/nmat4098

For decades now, silicon has been the workhorse of the microelectronics revolution and a key enabler of the information age. Owing to its excellent optical properties in the near- and mid-infrared, silicon is now promising to have a similar impact on photonics. The ability to incorporate both optical and electronic functionality in a single material offers the tantalizing prospect of amplifying, modulating and detecting light within a monolithic platform. However, a direct consequence of silicon’s transparency is that it cannot be used to detect light at telecommunications wavelengths. Here, we report on a laser processing technique developed for our silicon fibre technology through which we can modify the electronic band structure of the semiconductor material as it is crystallized. The unique fibre geometry in which the silicon core is confined within a silica cladding allows large anisotropic stresses to be set into the crystalline material so that the size of the bandgap can be engineered. We demonstrate extreme bandgap reductions from 1.11 eV down to 0.59 eV, enabling optical detection out to 2,100 nm. The electronic band structure in silicon optical fibres can be engineered by continuous laser irradiation during the crystallization of the fibres. A reduction of the bandgap down to 0.59 eV is demonstrated.