Researchers from the University of Texas at Arlington and the University of Wisconsin-Madison have conceptualized the design for a new laser to facilitate on-chip optical connections promoting high speed and energy efficiency.
Artist representation of on-chip laser design (Credit: Hongjun Yang.)
Edge-emitter lasers are considered as the ideal choice for on-chip optical connections. But these lasers are voluminous in comparison to available chip area and the mirrors are difficult to form, thereby impeding their use as optical links.
Surface-emitting lasers on the other hand could be a cheaper and better alternative owing to their extremely small size of just few micrometers. Even these are considered too big in relation to their silicon surroundings. In order to shrink the size of on-chip lasers, the researchers propose a solution in which two highly reflective photonic crystal mirrors replace the layers of reflectors necessary for conventional distributed Bragg reflector laser design. The mirrors are composed of compound semiconductor quantum well materials and silicon nano membranes are used to hold the mirrors in place.
Since one layer of photonic crystal is equivalent to 15 to 30 layers of dielectric reflectors employed in existing lasers, the former makes it possible to produce 2 µm high lasers for optical connections with performance on par with current designs. Optical data links are employed at the higher levels of data networks such as connections between countries and cities. The data at the lower echelons such as from regional hub to home is still transmitted through slow metal connections. The research team is hopeful of a move to optical connections at all levels through their design which would be an important contributor to high speed computer processing.