Dispersive gain and loss in midinfrared quantum cascade laser

Abstract

We report the measurements of dispersive gain (simultaneous coexistence of gain and losses on a single intersubband transition) in a quantum cascade laser. Broadband transmission spectra through the waveguide of a Lambda ~4.7 µm In0.53Ga0.47As/AlAs0.56Sb0.44/InP quantum cascade laser have been studied at a bias below laser threshold and at different temperatures. For a certain range of current, and at temperatures higher than about 150 K, the transmission spectra show clear dispersive gain/loss behavior with the possibility for intersubband gain to be observed even without global population inversion between laser levels

Impact of intersubband dispersive gain in semiconductor quantum optics

“…It has been recently demonstrated that a judicious combination of material and design parameters can lead to conduction bands with dispersion relation characterized with lower masses on top and heavier masses in lower subbands, thus allowing for local inversion in k-space and gain even though there is no global population inversion [11]. This study demonstrates that for similar effective masses, dispersive gain is recovered as expected [12,13], but for masses engineered to be sufficiently different there is a deviation from the dispersive shape.…”

Intersubband gain without global inversion through dilute nitride band engineering

“…Furthermore it is interesting to notice that the dispersive gain expected for LWI 6,27 is found for similar effective masses. See Fig.…”

Simulation of gain in quantum cascade lasers

“…1(f), as recently observed in QCLs. 18,19 The same effect is common for superlattices where the total occupation f i (k) is identical for all Wannier-Stark states belonging to the lowest miniband. …”