Four-wave mixing in a silicon microring resonator using a self-pumping geometry

We report on four-wave mixing in a silicon microring resonator using a self-pumping scheme instead of an external laser. The ring resonator is inserted in an external-loop cavity with a fibered semiconductor amplifier as a source of gain. The silicon microring acts as a filter and we observe lasing in one of the microring's resonances. We study correlations between signal and idler generated beams using a Joint Spectral Density experiment

Exciton polaritons in two-dimensional photonic crystals

Experimental evidence of strong coupling between excitons confined in a quantum well and the photonic modes of a two-dimensional dielectric lattice is reported. Both resonant scattering and photoluminescence spectra at low temperature show the anticrossing of the polariton branches, fingerprint of strong coupling regime. The experiments are successfully interpreted in terms of a quantum theory of exciton-photon coupling in the investigated structure. These results show that the polariton dispersion can be tailored by properly varying the photonic crystal lattice parameter, which opens the possibility to obtain the generation of entangled photon pairs through polariton stimulated scattering.Comment: 5 pages, 4 figure

Highly Tunable Emission by Halide Engineering in Lead-Free Perovskite-Derivative Nanocrystals: The Cs2SnX6 (X = Cl, Br, Br/I, I) System

Nanocrystals of Cs2SnX6 (X = Cl, Br, Br0.5I0.5, and I) have been prepared by a simple, optimized, hot-injection method, reporting for the first time the synthesis of Cs2SnCl6, Cs2SnBr6, and mixed Cs2Sn(I0.5Br0.5)6 nanocrystalline samples. They all show a cubic crystal structure with a linear scaling of lattice parameter by changing the halide size. The prepared nanocrystals have spherical shape with average size from 3 to 6 nm depending on the nature of the halide and span an emission range from 444 nm (Cs2SnCl6) to 790 nm (Cs2SnI6) with a further modulation provided by mixed Br/I systems

Polariton Condensation and Lasing

The similarities and differences between polariton condensation in microcavities and standard lasing in a semiconductor cavity structure are reviewed. The recent experiments on "photon condensation" are also reviewed.Comment: 23 pages, 6 figures; Based on the book chapter in Exciton Polaritons in Microcavities, (Springer Series in Solid State Sciences vol. 172), V. Timofeev and D. Sanvitto, eds., (Springer, 2012

Suppression of Parasitic Nonlinear Processes in Spontaneous Four-Wave Mixing with Linearly Uncoupled Resonators

We report on a signal-to-noise ratio characterizing the generation of identical photon pairs of more than 4 orders of magnitude in a ring resonator system. Parasitic noise, associated with single-pump spontaneous four-wave mixing, is essentially eliminated by employing a novel system design involving two resonators that are linearly uncoupled but nonlinearly coupled. This opens the way to a new class of integrated devices exploiting the unique properties of identical photon pairs in the same optical mode

Bistability in the Tunnelling Current through a Ring of NN Coupled Quantum Dots

We study bistability in the electron transport through a ring of N coupled quantum dots with two orbitals in each dot. One orbital is localized (called b orbital) and coupling of the b orbitals in any two dots is negligible; the other is delocalized in the plane of the ring (called d orbital), due to coupling of the d orbitals in the neighboring dots, as described by a tight-binding model. The d orbitals thereby form a band with finite width. The b and d orbitals are connected to the source and drain electrodes with a voltage bias V, allowing the electron tunnelling. Tunnelling current is calculated by using a nonequilibrium Green function method recently developed to treat nanostructures with multiple energy levels. We find a bistable effect in the tunnelling current as a function of bias V, when the size N>50; this effect scales with the size N and becomes sizable at N~100. The temperature effect on bistability is also discussed. In comparison, mean-field treatment tends to overestimate the bistable effect.Comment: Published in JPSJ; minor typos correcte

Transmittance and optical constants of ca films in the 4-1000 eV spectral range

8 págs.; 8 figs.; OCIS codes: (260.7200) Ultraviolet, extreme; (120.4530) Optical constants; (350.2450) Filters, absorption; (230.4170) Multilayers; (310.6860) Thin films, optical properties.© 2015 Optical Society of America. The low expected absorption of Ca in the extreme ultraviolet (EUV) makes it an attractive material for multilayers and filters because most materials in nature strongly absorb the EUV. Few optical constant data had been reported for Ca. In this research, Ca films of various thicknesses were deposited on gridsupported C films and their transmittance measured in situ from the visible to the soft x-rays. The measurement range contains M2,3 and L2,3 absorption edges. Transmittance measurements were used to obtain the Ca extinction coefficient k. A minimum k of 0.017 was obtained at ∼23 eV, which makes Ca a promising low-absorption material for EUV coatings. A second spectral range of interest for its low absorption is below the Ca L3 edge at ∼343 eV. Measured k data and extrapolations were used to calculate the refractive index n using Kramers.Kronig relations. This is the first self-consistent data set on Ca covering a wide spectral range including the EUV.We acknowledge support by the European Community—Research Infrastructure Action under the FP6 “Structuring the European Research Area” Programme (through the Integrated Infrastructure Initiative “Integrating Activity on Synchrotron and Free Electron Laser Science”) through proposal number Ref. 2007655. This work was also supported by the National Programme for Space Research, Subdirección General de Proyectos de Investigación, Ministerio de Ciencia y Tecnología, project numbers AYA2010-22032 and AYA2013-42590-P. L. Rodrí- guez-de Marcos and S. García-Cortés are thankful to Consejo Superior de Investigaciones Científicas (CSIC) for funding under the Programa JAE, partially supported by the European Social Fund. M. Vidal-Dasilva acknowledges financial support from an FPI fellowship number BES-2006-14047Peer Reviewe

Strong Light-Matter Interaction between Guided Bloch Surface Waves and Quantum-Well Excitons

We report on a theoretical investigation of guided polariton states arising from the strong coupling between a single quantum-well exciton and a Bloch Surface Wave in a multi-layered structure. We show that the polariton Rabi splitting can be increased by almost 40% as compared to that achievable in a similar structure made in a conventional planar microcavity. Moreover, we theoretically demonstrate that by simple engineering of the sample surface with oxide deposition, one can obtain 1D polaritons propagating within the structure. The latter result shows the usefulness of our proposed device as a key component for the realization of "polaritonic integrated circuits"

A step beyond in steady-state and time-resolved electro-optical spectroscopy: Demonstration of a customized simple, compact, low-cost, fiber-based interferometer system

Electro-optical spectroscopy is nowadays a routine approach for the analysis of light induced properties and dynamical processes in matter, whose understanding is particularly crucial for the intelligent design of novel synthetic materials and the engineering and optimization of high-impact optoelectronic devices. Currently, within this field, it is the common choice to rely on multiple commercial setups, often costly and complex, which can rarely combine multiple functions at the same time with the required sensitivity, resolution, and spectral tunability (in both excitation and detection). Here, we present an innovative, compact, and low-cost system based on "three in one"components for the simultaneous electro-optical material and device characterization. It relies on compact fiber-coupled Fourier transform spectroscopy, the core of the system, enabling a fast spectral analysis to acquire simultaneously wavelength and time resolved photoluminescence (PL) maps (as a function of the time and wavelength), PL quantum yield, and electroluminescence signal. Our system bypasses conventional ones, proposing a new solution for a compact, low-cost, and user-friendly tool, while maintaining high levels of resolution and sensitivity