The Significance of Carrier Leakage for Stable Lasing in Split-Well Direct Phonon Terahertz Quantum Cascade Lasers

The effects of longitudinal-optical phonon scattering and dephasing in quantum cascade structures are studied. Three-level longitudinal-optical phonon depopulated terahertz structures are investigated using a density matrix Monte Carlo method. Ideally, these structures do not contain energy states above the upper lasing state, which in principle, can reduce parasitic leakage. The light output and current density as a function of lattice temperature are calculated and shown to be consistent with experiment for a recently reported structure that is confirmed to be a good approximation to a three-level structure. The pure dephasing time is self-consistently found to be relatively constant over the temperature range, which differs from the previous analysis of other structures. At higher lattice temperatures, particularly at elevated temperatures beyond the lasing point, the reduction in current density is rather due largely to rapid longitudinal-optical phonon absorption, which reduces the lifetime of the ground state. It is shown that the operating temperature limit may further be improved by adequately increasing the injector anticrossing.

show abstract

Two-well injector direct-phonon terahertz quantum cascade lasers

Gower

Levy

Piperno

et al. 2023

Applied Physics Letters

View full text Add to dashboard Cite

We present an experimental study on a terahertz quantum cascade laser (THz QCL) design that combines both two-well injector and direct-phonon scattering schemes, i.e., a so-called two-well injector direct-phonon design. As a result of the two-well injector direct-phonon scheme presented here, the lasers benefit from both a direct phonon scattering scheme for the lower laser level depopulation and a setback for the doping profile that reduces the overlap of the doped region with active laser states. Additionally, our design also has efficient isolation of the active laser levels from excited and continuum states as indicated by negative differential resistance behavior all the way up to room temperature. This scheme serves as a good platform for improving the temperature performance of THz QCLs as indicated by the encouraging temperature performance results of the device with a relatively high doping level of 7.56 × 1010 cm−2 and Tmax ∼ 167 K. With the right optimization of the molecular beam epitaxy growth and interface quality, the injection coupling strength, and the doping density and its profile, the device could potentially reach higher temperatures than the latest records reached for the maximum operating temperature (Tmax) of THz QCLs.

show abstract

The Significance of Carrier Leakage for Stable Lasing in Split-Well Direct Phonon Terahertz Quantum Cascade Lasers

Cited by 10 publications

References 24 publications

High-temperature terahertz quantum cascade lasers

High-temperature terahertz quantum cascade lasers

Longitudinal-optical phonon absorption and dephasing in three-level terahertz quantum cascade structures with different injector anticrossings

Two-well injector direct-phonon terahertz quantum cascade lasers

Contact Info

Product

Resources

About