Intersubband devices

Intersubband nanostructures are the key enabling technology for long-wavelength optoelectronics. Because mid-infrared and terahertz wavelengths are below the bandgap of most semiconductor materials, one cannot rely on interband transitions when manipulating them. Instead, one must rely on intersubband transitions, devices that exploit the quantum nature of electrons to make artificial atoms. Perhaps the most famous intersubband device is the quantum cascade laser (QCL), a semiconductor source of light at these wavelengths that is chip-scale. A key theme of our work is the design and characterization of new intersubband systems—particularly terahertz QCLs—as well as projects in other areas, such as non-von Neumann computing.

A basic quantum cascade laser design. The layers are nanometers thick, and as a result the quantum properties of electrons manifest in these structures. This enables interaction with long-wavelength light.

Gain measurements of a terahertz quantum laser as a function of device bias. Quantum effects (such as anticrossings) are evident in these spectra, and one can even find many of the relevant optical transitions.

Dynamics of the dispersion of a terahertz quantum cascade laser material. This is highly relevant for applications like frequency comb formation.


  1. Y. Yang, A. Paulsen, D. Burghoff, J. L. Reno, and Q. Hu, “Lateral Heterogeneous Integration of Quantum Cascade Lasers,” ACS Photonics, vol. 5, no. 7, pp. 2742–2747, Jul. 2018. (link)
  2. D. Burghoff, Y. Yang, J. L. Reno, and Q. Hu, “Dispersion dynamics of quantum cascade lasers,” Optica, vol. 3, no. 12, p. 1362, Dec. 2016. (pdf, supplementary)
  3. N. Han, A. de Geofroy, D. P. Burghoff, C. W. I. Chan, A. W. M. Lee, J. L. Reno, and Q. Hu, “Broadband all-electronically tunable MEMS terahertz quantum cascade lasers,” Opt. Lett., vol. 39, no. 12, p. 3480, Jun. 2014. (link)
  4. D. Burghoff, C. Wang Ivan Chan, Q. Hu, and J. L. Reno, “Gain measurements of scattering-assisted terahertz quantum cascade lasers,” Appl. Phys. Lett., vol. 100, no. 26, p. 261111, Jun. 2012. (pdf)
  5. D. Burghoff, T.-Y. Kao, D. Ban, A. W. M. Lee, Q. Hu, and J. Reno, “A terahertz pulse emitter monolithically integrated with a quantum cascade laser,” Appl. Phys. Lett., vol. 98, no. 6, p. 061112, Feb. 2011. (pdf)