TI-QCL Energy Band Diagram.

Mid-wave infrared (MWIR) emissions are useful for a variety of applications ranging from communication to remote chemical sensing. The ability to produce efficient, modulatable, and coherent MWIR sources can help propel current technologies in these fields and enable new innovations. While standard quantum cascade lasers (QCLs) are one common solution for MWIR lasers, the transistor-injected quantum cascade laser (TI-QCL) presents a novel approach with several key advantages over conventional QCL devices. The added capability of the TI-QCL to separably control output power and emission wavelength enable or enhance more applications, such as spectroscopic measurements. Previous designs of the TI-QCL have demonstrated proper transistor function but have failed to produce coherent MWIR light. Recent focus has been put on improving both device design and processing control in pursuit of a fully functional and efficient device.

Related News + Publications

• Robert Presents QCL Work at CS MANTECH 2025
  Robert Kaufman presents his talk titled, “Impurity-Induced Disordering of InGaAs/InAlAs Superlattices by Zinc Diffusion for Electrical Confinement in Quantum Cascade Lasers” at CS MANTECH 2025.
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  Robert Presents TI-QCS Research at CS MANTECH 2024
  At the 2024 CS MANTECH conference, Robert presents his work finding unique device physics in his transistor injected quantum cascade structure (TI-QCS).
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  Ultra-sensitive current bistability and light switching in a resonant tunneling superlattice transistor
  Bistability in the current–voltage characteristics of semiconductor superlattices and quantum cascade laser structures has the potential for wide-ranging applications, particularly in sensing systems. However, the interdependency of applied bias and current injection in conventional two-terminal structures has led to complications in analysis and rendered the bistability phenomenon difficult to implement in practical applications. Here, we… Read more: Ultra-sensitive current bistability and light switching in a resonant tunneling superlattice transistor
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  Robert, Kevin, and Leah Present at the Engineering Research Fair
  Robert Kaufman, Kevin Pikul, and Leah Espenhahn present a high-level view on the research conducted within the group at the 2023 Engineering Research Fair. Over the course of two hours, 74 undergraduate students show interest in the group and the research being performed.
• Design and Fabrication Considerations for Transistor-Injected Quantum Cascade Lasers for Compact, Efficient, and Controllable Mid-Wave Infrared Lasing
  The transistor-injected quantum cascade laser (TI-QCL) is a novel design for a mid-wave infrared (MWIR) laser that seeks to overcome some of the primary limitations of standard quantum cascade lasers (QCLs). By growing the active cascade region within the base-collector junction of an npn heterojunction bipolar transistor (HBT), independent control of the injection current and… Read more: Design and Fabrication Considerations for Transistor-Injected Quantum Cascade Lasers for Compact, Efficient, and Controllable Mid-Wave Infrared Lasing