Electrically pumped quantum-dot near-IR microlaser on silicon has submilliamp threshold

Sept. 18, 2017
The 10-μm-diameter whispering-gallery-mode device emits light at 1.3 μm, is intended for integrated photonics.

Researchers from the Hong Kong University of Science and Technology (HKUST) and the University of California, Santa Barbara (UCSB) have now created record-small electrically pumped microlasers epitaxially grown on industry-standard (001) silicon (Si) substrates.1 The devices operate in a whispering-gallery-mode microlaser with a radius of 5 μm, have a submilliamp threshold of 0.6 mA, emit in the near-IR (1.3 μm), and operate at temperatures up to 100 °C. The thresholds and footprints are orders of magnitude smaller than those previously reported lasers epitaxially grown on Si, say the researchers.

It should be noted that a somewhat similar development was reported in 2016 by a group of researchers from University College London (London, England), the University of Sheffield (Sheffield, England), and Cardiff University (Cardiff, Wales).

III-V devices

The gallium arsenide (GaAs) based III-V semiconductor devices from HKURST and UCSB, which also incorporate aluminum (Al) and indium (In), consist of a GaAs layer on Si, 15 periods of thin (5 nm/5 nm) Al0.3Ga0.7As/GaAs layers, and seven InAs/InGaAs quantum dot-in-a-well layers in the laser's active region.

"The realization of high-performance micron-sized lasers directly grown on Si represents a major step toward utilization of direct III-V/Si epitaxy as an alternate option to wafer-bonding techniques as on-chip silicon light sources with dense integration and low power consumption," says Kei May Lau, a professor at HKUST.

From optical to electrical pumping

The two groups had previously developed optically-pumped continuous-wave (CW) microlasers operating at room temperature that were epitaxially grown on silicon with no germanium buffer layer or substrate miscut. "Electrical injection of microlasers is a much more challenging and daunting task: first, electrode metallization is limited by the micro-sized cavity, which may increase the device resistance and thermal impedance; second, the whispering gallery mode (WGM) is sensitive to any process imperfection, which may increase the optical loss," says Yating Wan, a HKUST PhD graduate who is now at UCSB.

"As a promising integration platform, silicon photonics needs on-chip laser sources that dramatically improve capability while trimming size and power dissipation in a cost-effective way for volume manufacturability," says John Bowers, deputy chief executive officer of AIM Photonics (Rochester, NY), a consortium devoted to developing the U.S integrated photonics industry. "The realization of high-performance micron-sized lasers directly grown on Si represents a major step toward utilization of direct III-V/Si epitaxy as an alternate option to wafer-bonding techniques."

Source: https://eurekalert.org/pub_releases/2017-09/hkuo-sd1091817.php

REFERENCE:

1. Yating Wan et al., Optics (2017); https://doi.org/10.1364/OPTICA.4.000940

About the Author

John Wallace | Senior Technical Editor (1998-2022)

John Wallace was with Laser Focus World for nearly 25 years, retiring in late June 2022. He obtained a bachelor's degree in mechanical engineering and physics at Rutgers University and a master's in optical engineering at the University of Rochester. Before becoming an editor, John worked as an engineer at RCA, Exxon, Eastman Kodak, and GCA Corporation.

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