Researchers at the University of California at Santa Barbara have demonstrated a novel quantum dot laser that not only is grown on silicon but that performs as well as similar lasers grown on their native substrates.
The researchers believe the work is an important step toward large-scale photonic integration in an ultra-low-cost platform.
While photonic devices offer an energy-efficient alternative to traditional copper network links for information transmission, these devices are also almost always prohibitively pricey.
One way to bring those costs down is to make photonics compatible with the existing silicon microelectronics industry. A promising way to do that is by growing "quantum dot" lasers directly on silicon substrates, according to graduate student Alan Y. Liu and his colleagues.
Although such quantum dot lasers have been grown on silicon before, their performance has not equaled those of quantum dot lasers grown on their native substrates, which are platforms made of materials similar to the quantum dot lasers themselves.
A quantum dot laser is similar in design to a quantum well laser, but the sheets of quantum well materials are replaced with a high density of smaller dots, each a few nanometers high and tens of nanometers across.
"Quantum wells are continuous in two dimensions, so imperfections in one part of the well can affect the entire layer. Quantum dots, however, are independent of each other, and as such they are less sensitive to the crystal imperfections resulting from the growth of laser material on silicon," Liu said.
The team grew quantum dots directly on silicon substrates using molecular beam epitaxy, in which the entire laser can be grown continuously in a single run, “which minimizes potential contamination," according to Liu.
The team will discuss its record-breaking results achieved using such lasers at this year's OFC Conference and Exposition, being held March 9-13 in San Francisco.
Their work was published in Applied Physics Letters, 104, 041104 (2014).
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