Quantum cascade lasers (QCLs) are unipolar semiconductor lasers operating in the mid infrared region. Their emitted wavelength is defined by the separation of intersubband levels which can be tailored by band structure engineering. Due to the fact that the maximum conduction band offset in the GaAs/AlGaAs material system is 380 meV, the lowest directly accessible wavelength is roughly 7 μm. One...

The three-dimensional confinement of electrons and holes in the semiconductor quantum dot (QD) structure profoundly changes its density of states compared to the bulk semiconductor or the thin-film quantum well (QW) structure. The aim of this paper is to theoretically investigate the microwave properties of InAs/InP(311B) QD lasers. A new expression of the modulation transfer function is derive...

The gain-lever effect enhances the modulation efficiency of a semiconductor laser when compared to modulating the entire laser. This technique is investigated in a long-cavity multi-section quantum-dot laser where the length of the modulation section is varied to achieve 14:2, 15:1 and 0:16 gain-to-modulation section ratios. In this work, the gain-levered modulation configuration resulted in an...

The effect of enhanced rate of spontaneous emission on gain and lasing threshold of semiconductor microcavity lasers has not been discussed clearly. Some reports have suggested that the lasing threshold in microcavities could possibly be lowered due to the so-called Purcell effect. Here, we argue that gain in weakly coupled semiconductor cavities is a local phenomenon, which occurs due to stimu...