Laser Integration on Silicon Photonic Circuits Through Transfer Printing

New fabrication approach allows the massively parallel transfer of III-V coupons to a silicon photonic target wafer.

Air Force Research Laboratory, Arlington, Virginia

The purpose of this project was to develop a transfer printing process for the massively parallel integration of III-V lasers on silicon photonic integrated circuits. Silicon has long offered promise as the ultimate platform for realizing compact photonic integrated circuits (PICs). That promise stems in part from the material's properties: the high refractive-index contrast of silicon allows strong confinement of the optical field, increasing light-matter interaction in a compact space-a particularly important attribute for realizing efficient modulators and high-speed detectors.

To date, silicon-photonics applications have had to rely on external laser sources that feed the optical chip through optical fiber, or on flip-chip integration of separately fabricated laser diodes. Neither of those approaches is scalable to very large wafer volumes or to more complex laser designs. Over the last few years, however, the research community has made tremendous strides toward realizing fully integrated laser diodes on silicon, both through wafer-bonding techniques that integrate direct-bandgap III-V epitaxial materials into prefabricated silicon circuits, and through direct epitaxy of III-V semiconductors on silicon.