Terahertz Quantum Cascade Lasers
Unipolar semiconductor injection lasers emitting at THz frequencies (4.3 THz, λ∼69 μm and 3.5 THz, λ∼85 μm) are discussed. The devices are based on interminiband transitions in chirped GaAs/AlGaAs superlattices that are arranged in a quantum-cascade scheme. The core featuring 100 repetitions of this type of superlattice, is embedded into a novel kind of waveguide loosely based on the surface plasmon concept, which allows to achieve low waveguide losses and high confiment factors. Continuous-wave laser emission is obtained with low tresholds of a few hundred A/cm2 up to 48 K heat sink temperature and maximum output powers of more than 4 mW. Under pulsed excitation, peak output powers of 4.5 mW at low temperatures and still 1 mW at 65 K are measured. The maximum operating temperature is 68 K. The operation of these devices is studied with the help of a Hakki-Paoli analysis.
KeywordsLower Laser Level Laser Level Quantum Cascade Laser Peak Output Power Threshold Current Density
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