Benjamin Williams
University of California-Los Angeles, CA·Engineering
Terahertz waves, with frequencies around 1 to 5 terahertz (THz) and wavelengths of tens to more than a hundred microns, can reveal the spectral fingerprints of gases and other materials. However, compact, powerful sources and sensitive detectors for this part of the spectrum are hard to build.
- Fields
Engineering
Physics
Materials Science
- Topics
terahertz
THz
quantum-cascade laser
- Grants
- 3 known grants, through Sep 2027
What they work on
- Demonstrate terahertz frequency combs, lasers emitting many evenly spaced colors, from quantum-cascade vertical-external-cavity surface-emitting lasers by developing new amplifying metasurfaces, fabrication processes and dispersion-compensation elements.
- Characterize the new terahertz combs in both frequency and time using coherent photonic techniques, and explore frequency-modulated quantum-walk combs and amplitude-modulated combs that produce ultrafast mode-locked pulses.
- Build a terahertz silicon interconnect fabric that uses chiplet technology to place silicon BiCMOS chips and III-V quantum-cascade amplifier chips side by side with micron-scale alignment for low-loss connections.
- Amplify weak terahertz signals from BiCMOS frequency-comb chips with quantum-cascade traveling-wave amplifiers to create a hybrid dual-comb transmitter and receiver for spectroscopy above 1.5 THz.
- Demonstrate multi-gas sensing with the hybrid electronic-photonic terahertz system, detecting the spectral fingerprints of several gases, including atmospheric environmental toxins.
- Grow lattice-matched Ge/SiGeSn quantum-well stacks with atomically sharp interfaces and characterize their electronic properties as a new group-IV material for intersubband devices.
- Use terahertz and far-infrared spectroscopy to show that designed intersubband transitions occur in Ge/SiGeSn quantum wells, culminating in a proof-of-concept demonstration of intersubband photoconductivity.
More about the research
The lab's three projects attack this problem from different directions: new laser designs that emit many precisely spaced colors, hybrid chips that combine silicon electronics with terahertz lasers for gas sensing, and a new silicon-compatible semiconductor material for far-infrared and terahertz devices. A shared tool is the quantum-cascade (QC) laser, a semiconductor laser whose light comes from electrons dropping between engineered energy levels in thin stacked layers.
Why it matters
Compact, powerful terahertz sources and detectors could improve gas sensing for residential air quality, pollutant monitoring, and industrial, energy and aerospace uses. They could also aid security screening, medical science and astrophysics. A silicon-compatible SiGeSn material could eventually allow terahertz and far-infrared lasers and detectors, possibly running at room temperature, to be made on standard 300-mm wafers in existing semiconductor foundries.
Known grants
From NIH and NSF research grants. Labs often have other funding we can't see.
NSF-SNSF: THz Frequency combs with Vertical-External-Cavity Surface-Emitting-Lasers
NSF · Oct 2024 – Sep 2027
FuSe: Electronic-photonic heterogeneous integration for sensing above 1 THz
NSF · Oct 2023 – Sep 2027
Collaborative Research: SiGeSn-based heterostructures for intersubband photonic materials
NSF · Aug 2023 – Jul 2027
Closest labs
Wei Du
University of Arkansas, AR·Engineering
Grow high-performance III-V semiconductor lasers on sapphire substrates by developing wafer-to-wafer covalent bonding, which joins two wafers with chemical bonds.
Amir Safavi-Naeini
Stanford University, CA·Engineering
Design and fabricate multilayer oxide-clad thin-film lithium niobate waveguides and resonators with low loss, high nonlinearity and low sensitivity to fabrication imperfections.
Melanie Reber
University of Georgia, GA·Chemistry·Early-career
Build ultrafast transient absorption spectroscopy inside external optical enhancement cavities, which recycle laser light through the sample, to reach the sensitivity needed to probe the low molecular densities of a molecular beam.
The school
University of California-Los Angeles: 84 labs on PI Pages, $1.9B a year on research, 803 research doctorates a year.
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