Resonant Exciton Scattering Reveals Raman Forbidden Phonon Modes in Layered GeS.

Germanium monosulfide with an anisotropic puckered crystalline structure has recently attracted much attention due to its unique optical and electronic properties; however, exciton-phonon interactions were only superficially elucidated. We study the resonant Raman scattering and the photoluminescence of the optically active Γ-exciton in layered GeS flakes and evaluate the exciton and phonon responses on variations in the excitation energy, laser-light and emission polarizations, temperature, and laser power. A double-resonance mechanism allows for observing Raman forbidden (dark) first- and second-order longitudinal-optical phonon modes whose symmetries and energies are moreover calculated by density functional perturbation theory.

Towards Interband Cascade lasers on InP Substrate.

In this study, we propose designs of an interband cascade laser (ICL) active region able to emit in the application-relevant mid infrared (MIR) spectral range and to be grown on an InP substrate. This is a long-sought solution as it promises a combination of ICL advantages with mature and cost-effective epitaxial technology of fabricating materials and devices with high structural and optical quality, when compared to standard approaches of growing ICLs on GaSb or InAs substrates. Therefore, we theoretically investigate a family of type II, "W"-shaped quantum wells made of InGaAs/InAs/GaAsSb with different barriers, for a range of compositions assuring the strain levels acceptable from the growth point of view.

Optical Measurements and Theoretical Modelling of Excitons in Double ZnO/ZnMgO Quantum Wells in an Internal Electric Field.

In this paper, the photoluminescence spectra of excitons in ZnO/ZnMgO/ZnO double asymmetric quantum wells grown on a-plane Al2O3 substrates with internal electric-field bands structures were studied. In these structures, the electron and the hole in the exciton are spatially separated between neighbouring quantum wells, by a ZnMgO barrier with different thickness. The existence of an internal electric field generates a linear potential and, as a result, lowers the energy of quantum states in the well.

Carrier transfer efficiency and its influence on emission properties of telecom wavelength InP-based quantum dot - quantum well structures.

We investigate a hybrid system containing an InGaAs quantum well (QW), separated by a thin 2 nm InGaAlAs barrier from 1.55 µm emitting InAs quantum dots (QDs), grown by molecular beam epitaxy on an InP substrate. Photoreflectance and photoluminescence (PL) spectroscopies are used to identify optical transitions in the system, with support of 8-band kp modelling.