Abstract
The state of the art terahertz-frequency quantum cascade lasers have opened a plethora of applications over the past two decades by testing several designs up to the very limit of operating temperature, optical power and lasing frequency performance. The temperature degradation mechanisms have long been under the debate for limiting the operation up to 210 K in pulsed operation in the GaAs/AlGaAs material system. In this work, we review the existing designs and exploit two main temperature degradation mechanisms by presenting a design in which they both prove beneficial to the lasing operation by dual pumping and dual extracting lasing levels. We have applied the density matrix transport model to select potential candidate structures by simulating over two million active region designs. We present several designs which offer better performance than the current record structure.
Highlights
Quantum cascade lasers (QCLs) have been initially proposed by Kazarinov and Suris in 1971 [1] as periodic two level resonant tunnelling superlattice structures
A variety of designs [6] generated structures with lasing frequencies in the range 1.2–5.6 THz [7,8,9,10], with high output power [11] and with operating temperature up to 210 K [12,13] in pulsed and 129 K [14] in continuous wave (CW) operation. These limits have all been achieved in GaAs/AlGaAs heterojunction superlattice which has shown the best performance for THz technology, the hope for improvement currently lies in other material systems [15,16] which exhibit better material parameters, but require further technology improvements
Lasing process in THz QCL is based on the same principles as in almost all other semiconductor, solid or gas lasers: lasing transition occurs between two levels – upper lasing level (ULL) and lower lasing level (LLL) where the main aim is to maintain population inversion by efficiently injecting carriers into ULL and extracting them from LLL
Summary
Quantum cascade lasers (QCLs) have been initially proposed by Kazarinov and Suris in 1971 [1] as periodic two level resonant tunnelling superlattice structures. A variety of designs [6] generated structures with lasing frequencies in the range 1.2–5.6 THz [7,8,9,10], with high output power [11] and with operating temperature up to 210 K [12,13] in pulsed and 129 K [14] in continuous wave (CW) operation (without the assistance of external magnetic field) These limits have all been achieved in GaAs/AlGaAs heterojunction superlattice which has shown the best performance for THz technology, the hope for improvement currently lies in other material systems [15,16] which exhibit better material parameters, but require further technology improvements. We used our numerically highly efficient density matrix transport model [20,21] that allowed brute–force search by simulating over two million candidate structures
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