Silicon forms the basis of everything from solar cells to the integrated circuits at the heart of our modern electronic gadgets. However the laser, one of the most ubiquitous of all electronic devices today, has long been one component unable to be successfully replicated in this material. Now researchers have found a way to create microscopically-small lasers directly from silicon, unlocking the possibilities of direct integration of photonics on silicon and taking a significant step towards light-based computers.
Whilst there has been a range of microminiature lasers incorporated directly into silicon over the years, including melding germanium-tin lasers with a silicon substrate and using gallium-arsenide (GaAs) to grow laser nanowires, these methods have involved compromise. With the new method, though, an international team of researchers has integrated sub-wavelength cavities, the basic components of their minuscule lasers, directly onto the silicon itself.
To help achieve this, a team of collaborating scientists from Hong Kong University of Science and Technology, the University of California, Santa Barbara, Sandia National Laboratories and Harvard University, first had to find a way to refine silicon crystal lattices so that their inherent defects were reduced significantly enough to match the smooth properties found in GaAs substrate lasers. They did this by etching nano-patterns directly onto the silicon to confine the defects and ensure the necessary quantum confinement of electrons within quantum dots grown on this template.
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