Research

Epitaxial Nanophotonics & Integrated Design

The design philosophy underneath everything else in the lab.

Optoelectronic device design usually privileges the electron over the photon. The APD Lab’s core belief is that epitaxial nanophotonics, coupled with an integrated design approach, is pivotal to advancing next-generation optoelectronic devices.

That means working in two paradigms at once. In the photonic paradigm we manipulate material geometry and permittivity to strengthen light–matter interaction. In the electronic paradigm we tune band structure to amplify functionality or serve the photonic design. Holding both together demands a comprehensive understanding of the electronic, photonic, and atomic attributes of semiconductor materials.

The payoff has been a broad family of enhanced devices across many materials, wavelengths, and applications — brighter luminescence, improved device response, lower noise, and substantially higher detector operating temperatures.

Quantum-limit Devices

Nanophotonic avalanche photodiodes chasing single-photon sensitivity.

Epitaxial nanophotonic avalanche photodiodes (APDs) hold significant promise for quantum-limit single-photon detectors (SPDs). No single SPD technology today possesses every necessary characteristic at once, and that gap is the opening we work in. Our emphasis is on the design, growth, fabrication, and thorough characterization of nanophotonic SPDs.

The reach extends well past quantum information science. APDs underpin medical imaging — fluorescence lifetime imaging microscopy, positron emission tomography, Cherenkov detection — as well as LIDAR and other consumer sensing.

UVC Laser Diodes

Pseudomorphic digital alloys for a laser diode that has resisted the field for decades.

A practical, electrically injected laser diode in the ultraviolet-C remains one of the outstanding challenges in compound semiconductor optoelectronics. We approach it through pseudomorphic digital alloys — short-period AlN/GaN superlattices grown strain-matched to the underlying template — which decouple the composition needed for deep-UV gain from the dislocation generation that ordinarily accompanies it.

This work runs on Pomelo, the lab’s nitride MBE system, with its nitrogen plasma source, scandium cell, and custom photo-enhanced growth capability.

High-index Photonic Modes & Devices

Exotic modes that only exist once the refractive index is high enough.

Some optical modes are simply unavailable at low index contrast. We identify and explore nanophotonic structures supporting modes exclusive to high-index systems — guided mode resonances, bound states in the continuum, and Mie-type photonic modes — then put them to work in real detectors and emitters.

Hybridizing these resonances is how we push infrared detector performance and operating temperature past what a conventional absorber-limited design allows.