A GaAs/AlAs planar cavity containing a collection of InAs quantum boxes in its core region has been grown in a single step by molecular beam epitaxy, and processed by electron-beam lithography and reactive ion etching into pillar microresonators. The optical study by photoluminescence of these localized light emitters allows a systematic and precise determination of the energies of the first confined photon modes of such microstructures, in good agreement with theoretical estimates. More generally, such probes facilitate the experimental study of the modes of complex photonic microstructures and of the spontaneous emission alteration they entail on a quasimonochromatic light emitter.

We experimentally demonstrate that a type-II pulsed optical parametric amplifier operated in a phaseinsensitive configuration works as a near-perfect classical optical amplifier whose noise figure approaches 3 dB at high gains. We further demonstrate that, when operated in a phase-sensitive configuration, this amplifier works as a quantum-optical amplifier whose noise figure goes below 3 dB and approaches 0 dB at high gains. The noise figure of 1.45 + 0.2 dB, measured for a gain of 9 dB, is clearly in the quantum regime.

Perovskite solar cell technology is fast approaching its first commercial deployment, with the 10‐year mark since the first research having passed recently. Commercial entrance seems very tangible, but there are a number of remaining challenges related to various economic and technical factors. Conventional photovoltaic markets, such as utility scale photovoltaics, are quite rigid and very demanding for a new entrant. Perovskites offer several new value propositions, which offer monetization prospects in the near future, if properly used. In particular, functionalities such as flexibility, high specific power, and good low‐light performance enable new applications and broadening of the conventional PV usage. The specific cases of internet of things and building‐integrated photovoltaics are discussed, and market opportunities are analyzed. Technology incubation with simultaneous market presence in emerging applications can provide essential economic stability and time for the technology to develop into its full potential. Opportunities in high‐value markets and massive‐scale deployment are also addressed, with the analysis of potentially disruptive offerings being promised by perovskite photovoltaic technology.

We demonstrate experimentally that a type-II pulsed optical parametric amplifier can duplicate (or, clone) a signal in the quadrature it amplifies. Although this device is an amplifier with large gain, it meets the quantitative criteria for quantum nondemolition measurements and, thus, operates in the nonclassical regime. It can be used as a noiseless amplifying optical tap which, at the same time, can overcome the noise introduced downstream by propagation and detection losses.PACS numbers: 42.50.Dv, 42.50.Lc, 42.65.Ky Type-II parametric amplifiers are known to produce various quantum effects, such as twin beams [1,2], squeezing [3][4][5], quantum nondemolition (QND) measurements [6], and Einstein-Podolsky-Rosen correlations [7]. Pulsed operation of such amplifiers [2,4-6] is particularly attractive because it eliminates the need for a resonant cavity and its bandwidth limitations. However, the high intensities of pulsed operation produce distortions of the wave fronts of the amplified signals and make subsequent homodyne detection of squeezed light very difficult [8]. Thus, large quantum effects involving high-intensity pulses have so far been restricted to twin beams, obtained in a phase-insensitive configuration [2].Another experimental configuration that should permit observation of significant quantum effects in pulsed operation consists, essentially, of a twin-beam setup with phase-dependent amplification. In this setup, an input beam is injected in a potassium titanyl phosphate (KTP) crystal at an angle of 45° from the crystal axes and undergoes phase-sensitive amplification. The output beam is split into two equal parts by a polarizer with transmission and reflection axes parallel to the crystal axes [see Fig. 1(a)]. When the input beam is amplified, the noise of the difference of the intensities of the two output beams drops below the shot-noise limit: This is the wellknown "twin-beam" effect, due to the fact that the signal and idler photons are produced in pairs. This scheme can be reinterpreted in an alternate way by regarding the type-II parameteric amplifier as a pair of two type-I amplifiers of inverse gains, each acting on a separate polarization [see Fig. 1(b)]. One amplifier amplifies the input beam in a phase-sensitive (and, therefore, noiseless [9]) way, whereas the second amplifier deamplifies the vacuum that enters in the polarization orthogonal to the input signal. At the exit of the KTP crystal, the amplified signal is split by the polarizing beam splitter, with squeezed vacuum entering into the "unused" port. The squeezed vacuum has the appropriate modal shape and phase to minimize the beam splitting noise, as seen in the twin-photon viewpoint. Thus, in the overall setup, noiseless amplification is automatically followed by noiseless optical tapping. In the high gain limit, both the mean field and the fluctuations of the amplified quadrature component are "magnified" and copied onto the two output beams emerging from the polarizer which are, therefore, "clones," that is, identical to ...

The optical losses in dry-etched monolithic microresonators have been studied as a function of their lateral dimensions. Cylindrical microresonators with various radii have been etched from a planar GaAlAs/GaAs microcavity with a very high quality factor (Q≅11 700). Measurements of the resonance linewidth, using Ti-sapphire laser spectroscopy allowed to study the degradation of the Q factor at small radii. The Q factor is four times smaller in 1.1 μm radius microresonators, compared to the unprocessed cavity. This degradation is attributed to optical scattering from sidewalls, whose efficiency is shown to scale with the guided mode intensity at the microresonator edge.

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Advanced electron microscopy techniques are combined for the first time to measure the composition, strain, and optical luminescence, of InGaN/GaN multi-layered structures down to the nanometer scale. Compositional fluctuations observed in InGaN epilayers are suppressed in these multi-layered structures up to a thickness of 100 nm and for an indium composition of 16%. The multi-layered structures remain pseudomorphically accommodated on the GaN substrate and exhibit single-peak, homogeneous luminescence so long as the composition is homogeneous. V C 2015 AIP Publishing LLC. [http://dx.