UCSB researchers boost efficiency of quantum-dot lasers on silicon

A group at the University of California at Santa Barbara (UCSB) is lowering the cost of laser sources on silicon-photonic chips by growing efficient quantum dot (QD) lasers directly on silicon substrates using molecular beam epitaxy (MBE). Although such QD lasers have been grown on silicon before, their performance has not equaled that of QD lasers grown on their native substrates (platforms made of similar semiconductor materials as the QD lasers themselves).

The researchers believe the work is an important step towards large-scale photonic integration in an ultralow-cost platform. The UCSB team will discuss its results at this year's OFC Conference and Exposition (March 9-13; San Francisco, CA).

Currently, quantum well lasers are used for data transmission. "Quantum wells are continuous in two dimensions, so imperfections in one part of the well can affect the entire layer," says UCSB graduate student Alan Liu. "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. Because of this, we can grow these lasers on larger and cheaper silicon substrates. And because of their small size, they require less power to operate than quantum well lasers while outputting more light, so they would enable low-cost silicon photonics."

Using MBE, "the entire laser can be grown continuously in a single run, which minimizes potential contamination," says Liu.

Presentation W4C.5. titled "High Performance 1.3μm InAs Quantum Dot Lasers Epitaxially Grown on Silicon" will take place Wednesday, March 12 at 5:00 p.m. in room 121 of the Moscone Center.

This work was recently published in Applied Physics Letters: Liu, A. Y. et al., "High performance continuous wave 1.3 μm quantum dot lasers on silicon." Applied Physics Letters, 104, 041104 (2014)