“At UCLA, the ECE Department has a storied history of excellence in education and innovation, and continuing and building upon that history will be my top priority.” – Benjamin Williams

Q. What are some of the main research projects that you are focusing on this academic year?
A: A big part of what we do in my lab is developing new sources of light — i.e. lasers — that operate in the terahertz (THz) spectral range. Light in this range has wavelengths of about 100 microns, which is about 100 times longer than light in the visible spectrum, but also about 100 times shorter than microwaves used for radar. However, it has historically been very difficult to generate light in this so-called “terahertz gap” in the spectrum, which has limited its practical use.

Semiconductor lasers are a convenient and efficient method to generate visible and infrared light. The exact wavelength emitted by the laser is determined by the bandgap energy of the semiconductor as an electron drops from the conduction band into the valence band, and the smaller the bandgap the longer wavelength the light. Unfortunately, suitable semiconductor materials for THz lasers — which have very small photon energies — don’t exist in nature.

Our group works on developing “quantum-cascade lasers,” in which quantum wells are engineered within the “artificial atoms” of semiconductors to provide energy states very close together, so that they emit the very small-energy THz photons.

Q: How do you work with undergraduate and graduate students on these research projects?
A: I have a number of graduate student researchers as well as undergraduate researchers that work in my lab. They are involved with everything from fundamental semiconductor material simulation and design, to semiconductor microfabrication, to electromagnetic and optical design, to laser characterization, to system development.

Q: How will your research be translated into new technologies?
A: Generation, detection, and manipulation of THz radiation enables a wide range of applications, including non-destructive evaluation and imaging in industrial settings, security screening, next-generation high-speed wireless communication, spectral identification of various solids and gases, pollution and atmospheric monitoring, astrophysical study of star-formation and the study of planetary and cometary atmospheres, and biomedical imaging.

We actively work with government labs and companies with the goal of translating our lab-based technologies into prototypes. Recently, we have been working to advance THz quantum-cascade lasers to serve as sources for spectroscopy, where the emitted wavelength can be swept over a large range while maintaining precise control. The THz range is often known as a “spectral fingerprint” range since many materials and gases can be identified by the specific THz wavelengths they absorb or emit. For example, we work with the Jet Propulsion Laboratory to qualify our lasers for use as precise frequency-referenced “local-oscillators” in future heterodyne receivers in astrophysics instruments. These are basically advanced radio receivers that detect the weak THz radiation emitted from particular atoms that make up star-forming regions. Knowing what atoms and molecules are present, their concentrations, their isotopic ratios, their temperature, and their ionization status all provide vital clues to questions about how stars are formed, the history of the early universe, and the origin of water (the key ingredient of life) within and outside the solar system.

Q: How could private funding through donor gifts enable you to further your research at UCLA?
A: First and foremost, donor support would help us fund graduate student fellowships. In my group, as in those of my colleagues, research success depends on being able to recruit and support the best and brightest students to work with us. These students bring fresh ideas, and are at the “tip of the spear” for achieving scientific breakthroughs. They go on to staff our country’s technology companies and government labs, or even start their own companies. Having support from donor gifts would allow us to provide secure lines of funding, so that students can focus on doing their best work. Second, private funding would allow us to tackle higher-risk research directions that require preliminary results before funding agencies or industry partners are ready to provide support.

Q: As the newly appointed chair of the Electrical and Computer Engineering (ECE) Department, could you discuss your key priorities and goals for the department moving forward? How does your department cultivate connections between students and faculty?
A: At UCLA, the ECE Department has a storied history of excellence in education and innovation, and continuing and building upon that history will be my top priority. This is an exciting time of great promise for new breakthroughs in a myriad of fields, and many of our faculty are at the forefront. However, it is also a time of great uncertainty with regards to federal funding, which threatens major parts of our department’s research. Most immediately, this potentially impacts our graduate students, who rely on this research funding to support their research.

Nonetheless, within these challenges lie opportunities. My first priority as chair is to work with our faculty and with the dean to establish new, and enhance existing, partnerships with industry, foundations, and donors. There is an incredible variety of exciting research being done in the department, ranging from fundamental theoretical work to highly applied systems that are poised to be spun off into companies. My second, more internal, focus is to enhance the sense of community and culture within the department, not only between faculty and students, but also including the staff and alumni. Each plays an instrumental role in our collective mission of educating the next generation of engineers and producing world-class research. In my first year, I will be talking with many to learn what is working and what can be improved.

Q: Which emerging applications of terahertz and infrared technologies do you find most compelling or impactful in the near term?
A: Right now, for example, we are proposing to use THz quantum-cascade lasers to identify hydrogen-fluoride (HF) gas, which is a very toxic byproduct of lithium-ion battery degradation. As large-scale lithium-ion battery installations have become more common for utility, commercial, and industrial power applications, sensing of HF can potentially identify battery hazards, particularly for first responders facing fires with unknown levels of HF. It turns out that THz absorption of HF is considerably stronger than in the infrared part of the spectrum. If we can advance the state of the appropriate THz laser instrumentation, this will enable detection of HF in battery installations in a much more sensitive fashion than is currently possible.