Spatial observation and optical manipulation of polariton quantum liquids are raising a large interest in the studies of polariton condensates in microcavities [1]. In this work, we report the study of polariton condensates in a semi-hybrid ZnO microcavity where the condensation of polaritons up to room temperature has been achieved. This cavity is based on high quality AlN/AlGaN DBRs on 200µm ∗ 200µm mesas. The obtention of a low condensation threshold in a microcavity is related to its local quality factor Q. However the generation of the condensate also strongly depends on the photonic disorderof the cavity i.e. on polariton localization. The purpose of this work is to demonstrate the influence of this last parameter using different large excitation shapes. Figure 1.a shows a cross sectional energy mapping below threshold of polaritons at negative detuning. It is done by scanning the sample with a focused CW excitation spot. The energy fluctuation is less than 4 meV and the local quality factor is above 1900. We then excite the sample with large excitation areas. The photoluminescence profile created by an elongated excitation (60µm ∗ 5µm) is shown on figure 1.b. The intensity profile indicates that the polariton condensate is not uniform. In fact we can clearly see the localization of polaritons on sitesthat can be separated by more than 10 µm . We assume that this effect is related to the photonic disorder. The impact of size and shape of the excitation area on the condensate intensity profile will be discussed.

We create polariton clouds and polariton condensates to characterize their propagation at different temperatures. Our experimental results show that in a thickness gradient microcavity, polariton propagation is mainly ballistic and does not depend on the microcavity gradient. Above threshold, we compare the experimental results to a theoretical model [1] to understand the peculiar k-space images of the polariton condensate. Our results indicate that these images are due to the repulsion of the condensate from the center of excitation by the exciton reservoir created by a small excitation spot (2~3 µm).

A platform for fabricating polariton lasers operating at room temperature is introduced: nitride-based distributed Bragg reflectors epitaxially grown on patterned silicon substrates. The patterning allows for an enhanced strain relaxation, thereby enabling to stack a large number of crack-free AlN/AlGaN pairs and achieve cavity quality factors of several thousands with a large spatial homogeneity. GaN and ZnO active regions are epitaxially grown thereon, and the cavities are completed with top dielectric Bragg reflectors. The two structures display strong-coupling and polariton lasing at room temperature and constitute an intermediate step in the way towardsintegrated polariton devices.

We demonstrate a two-dimensional free-standing gallium nitride photonic crystal platform operating around 1550 nm and fabricated on a silicon substrate. Width-modulated waveguide cavities are integrated and exhibit loaded quality factors up to 34 000 at 1575 nm. We show the resonance tunability by varying the ratio of air hole radius to periodicity, and cavity hole displacement. We deduce a 7.9 dB/cm linear absorption loss for the suspended nitride structure from the power dependence of the cavity in-plane transmission.

Terahertz power dependence of the photoresponse of field effect transistors, operating at frequencies from 0.1 to 3 THz for incident radiation power density up to 100 kW/cm2 was studied InGaAs high electron mobility transistors. The observed signal saturation behavior is explained by analogy with current saturation in standard direct currents output characteristics. The theoretical model of terahertz field effect transistor photoresponse was developed shows a good description match with experimental data. Our experimental results show that dynamic range of field effect transistors based terahertz detectors is very high and can extend from mW/cm2 up to kW/cm2.

When vitreous silica is submitted to high pressures under helium atmosphere, the change in volume observed is much smaller than expected from its elastic properties. 1 It results from helium penetration into the interstitial free volume of the glass network. We present here the results of concurrent spectroscopic experiments using either helium or neon and molecular simulations relating the amount of gas adsorbed to the strain of the network. We show that a generalized poromechanical approach, describing the elastic properties of microporous materials upon adsorption, can be applied success-fully to silica glass in which the free volume exists only at the sub-nanometer scale. In that picture, the adsorption-induced deformation accounts for the small apparent compressibility of silica observed in experiments.

Understanding the mechanism of biomolecules’ interaction with inorganic surfaces might pave the way for the design of material interfaces with controlled and highly predictable properties. Here we have focused on the adsorption mechanism of facet-specific amino acids in the sequence of peptides selected for programmed synthesis of Pt(111) and Pt(100) nanocrystals. Using the first principles calculations we have demonstrated that the specific surface recognition of amino acid side chains occurs due to the combination of multiple processes: electron exchange, partial charge transfer and/or dispersive effects providing a high binding affinity to both polar and non-polar residues against both Pt facets. Our approach points towards promising novel routes for controlled design of material-specific linkers for future materials engineering.