Optical Properties and Modal Gain of InGaN Quantum Dot Stacks

We present investigations of the optical properties of stacked InGaN quantum dot layers and demonstrate their advantage over single quantum dot layer structures. Measurements were performed on structures containing a single layer with quantum dots or threefold stacked quantum dot layers, respectively. A superlinear increase of the quantum dot related photoluminescence is detected with increasing number of quantum dot layers while other relevant GaN related spectral features are much less intensive when compared to the photoluminescence of a single quantum dot layer. The quantum dot character of the active material is verified by microphotoluminescence experiments at different temperatures. For the possible integration within optical devices in the future the threshold power density was investigated as well as the modal gain by using the variable stripe length method.Comment: 9 Pages, 4 Figure

Observation of a hybrid state of Tamm plasmons and microcavity exciton polaritons

We present evidence for the existence of a hybrid state of Tamm plasmons and microcavity exciton polaritons in a II-VI material based microcavity sample covered with an Ag metal layer. The bare cavity mode shows a characteristic anticrossing with the Tamm-plasmon mode, when microreflectivity measurements are performed for different detunings between the Tamm plasmon and the cavity mode. When the Tamm-plasmon mode is in resonance with the cavity polariton four hybrid eigenstates are observed due to the coupling of the cavity-photon mode, the Tamm-plasmon mode, and the heavy- and light-hole excitons. If the bare Tamm-plasmon mode is tuned, these resonances will exhibit three anticrossings. Experimental results are in good agreement with calculations based on the transfer matrix method as well as on the coupled-oscillators model. The lowest hybrid eigenstate is observed to be red shifted by about 13 meV with respect to the lower cavity polariton state when the Tamm plasmon is resonantly coupled with the cavity polariton. This spectral shift which is caused by the metal layer can be used to create a trapping potential channel for the polaritons. Such channels can guide the polariton propagation similar to one-dimensional polariton wires

Fabrication of ZnSe-based microcavities for lasing in the strong coupling regime and polariton confinement

International audienceWe report on the realization of monolithic, i.e. fully epitaxial ZnSe-based microcavities with a 1λ-cavity and a 3λ-cavity for the investigation of strong coupling phenomena. A crucial building block is the fabrication of a lattice matched distributed Bragg reflector for the blue spectral region, consisting of quaternary ZnMgSSe layers as the high-index material and a MgS/ZnCdSe superlattice as the low-index material. Strong coupling at low temperatures was achieved with a vacuum Rabi splitting of 19 meV for the 1λ-cavity (at 70K) and of 40 meV for the 3λ-cavity (at 7 K).Microstructures such as micropillars, waveguides, ringresonators, and molecule chains were fabricated using focused ion-beam etching. Discrete optical modes in micropillars were observed for both cavity lengths confirming three-dimensional optical confinement. Q-factors up to 6500 indicate a high optical quality