GaAs/Al x Ga 1−x As quantum cascade lasers

Abstract

A unipolar injection quantum cascade (QC) laser grown in an AlGaAs/GaAs material system by molecular beam epitaxy, is reported. The active material is a 30 period sequence of injectors/active regions made from Al0.33Ga0.67As/GaAs-coupled quantum wells. For this device a special waveguide design, which complies with a GaAs heavily doped substrate and very short Al0.90Ga0.10As cladding layers, has been optimized. At a heat-sink temperature of 77 K, the laser emission wavelength is 9.4 μm with peak optical power exceeding 70 mW and the threshold current density is 7.3 kA/cm2. The maximum operating temperature is 140 K. This work experimentally demonstrates the general validity of QC laser principles by showing laser action in a heterostructure material different from the one used until now.

Gain and loss in quantum cascade lasers

“…1. Calculated gain and absorption (g < 0) spectra for the QCL from [7]. Data for different voltage drops per period and corresponding current densities are displayed.…”

“…[7] using a fully selfconsistent quantum mechanical approach on the basis of nonequilibrium Green functions. We find that gain sets in for current densities around 1 kA/cm 2 and increases with current.…”

Photonic crystals in the optical regime — past, present and future

“…transitions between di!erent states in the same or neighbouring quantum wells and typically a multitude of these transitions is cascaded in order to provide su$cient gain. In most cases, InGaAs/InAlAs multilayers are used, but there has also been rapid progress in the GaAs/AlGaAs system [144,145]. The wavelength range demonstrated so far is between 3 m and 17 m.…”

Quantum wire intersubband emitter

“…From (1), the electrons tunnel into the next active region, where they perform another optical transition. This concept has so far been put into practice using the subbands of semiconductor heterostructures in quantum well systems [2][3][4]. The dimensionality of the quantum confinement does not enter into the operating principle, so it may also be conceived for an array of quantum wires with the electrons being transported normal to the direction of the wires.…”