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Terahertz quantum cascade lasers based on resonant phonon scattering for depopulation
Qing Hu1, Benjamin S Williams, Sushil Kumar
1Department of Electrical Engineering and Computer Science and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Summary
We developed terahertz (THz) quantum cascade lasers (QCLs) using resonant longitudinal optical phonon scattering for efficient depopulation. This novel THz QCL design achieves lasing at 3.4 THz and longer wavelengths.
Area of Science:
- Quantum electronics
- Terahertz (THz) technology
- Semiconductor lasers
Background:
- Quantum cascade lasers (QCLs) are semiconductor devices emitting coherent light.
- Mid-infrared QCLs commonly use resonant longitudinal optical (LO) phonon scattering for depopulation.
- Efficient depopulation mechanisms are crucial for high-temperature THz QCL operation.
Purpose of the Study:
- To develop terahertz (THz) quantum cascade lasers (QCLs) utilizing resonant LO-phonon scattering for lower radiative level depopulation.
- To investigate the performance of THz QCLs at high temperatures and high injection levels.
- To achieve lasing at longer THz wavelengths using advanced waveguide designs.
Main Methods:
- Designing THz QCL structures with resonant LO-phonon scattering for selective depopulation.
- Implementing a novel double-sided metal waveguide for enhanced mode confinement and reduced cavity loss.
- Characterizing laser performance, including operating temperature, frequency, and output power.
Main Results:
- Demonstrated THz QCLs with resonant LO-phonon scattering achieving lasing at 3.4 THz (87 microm) up to 87 K.
- Achieved peak power exceeding 10 mW at 40 K.
- Obtained lasing at wavelengths longer than 100 microm due to the effective waveguide design.
Conclusions:
- Resonant LO-phonon scattering is a robust and effective depopulation mechanism for high-temperature THz QCLs.
- The developed THz QCLs exhibit promising performance for various applications.
- Novel waveguide structures enable extended wavelength operation in THz QCLs.