Physically deposited plasmonic nanostructures offer an attractive route toward reproducible and scalable Surface-enhanced Raman spectroscopy (SERS) substrates, yet their analytical performance must be quantitatively linked to morphology and plasmonic coupling. Here, nanostructured Au substrates are fabricated by single-step electron-beam (e-beam) evaporation process and evaluated for ultrasensitive detection of Rhodamine B (RhB). Atomic force microscopy, scanning electron microscopy, and UV-VIS spectroscopy reveal a thickness-dependent evolution from isolated nanostructures to a network near the percoaltion threshold where electromagnetic hot spots dominate. An optimal nominal Au thickness of 7-8 nm is identified. Raman mapping over 15 locations yields a relative standard deviation (RSD) of 3.5\%, confirming excellent spatial uniformity. Substrate reusability is assessed through repeated adsorption and washing cycles in ethanol, where the recovered RhB signal remains at approximately 90\% of the initial intensity, with a cycle-to-cycle RSD of 8.5\%, while post-wash residual signals remain consistently low. Under the optimized conditions, RhB is detected down to a theoretical limit of detection of $8.5 \times 10^{-11}$ M and a representative average enhancement factor of $(1.01 \pm 0.67)\times10^{6}$ is obtained in the low-coverage regime. These results show that the SERS response is governed by interparticle coupling and collective plasmonic effects rather than isolated nanoparticle resonances, and demonstrate that e-beam evaporated Au nanostructure networks provide a robust and competitive SERS platform with a fabrication route that is rapid, reproducible, and compatible with large-area sensor integration.

Metal-organic frameworks (MOFs) crystals are promising emerging materials for terahertz (THz) photonics i.e., for THz wave generation through difference frequency or optical rectification and electrooptic detection, including optical components for THz beam steering. The present work reports optical properties of three different non-centrosymmetric single MOF crystals, grown by an innovative solvo-thermal technique with tunable morphology, termed MOF [Zn(3-ptz)2]n (MIRO-101). THz time-domain spectroscopy (TTDS) in the range of 0.25 - 1.5 THz has been used for the measurement of the transfer function, H(w) of these MOF crystals. Through this experimental function Hexp(w), optical parameters such as refractive index, nMOF(w) and absorption coefficient, aMOF(w) have been calculated for the analysis of the optical properties of this crystal. The results indicate that this MOF crystal offers opportunities for long-term exploration of properties toward the creation of novel nonlinear THz photonics materials, as a THz radiation emitter via Different Frequency Generation (DFG) or Optical Rectification (OR) and Electro-optic (EO) detection via optical sampling, including for its use in optoelectronics, and materials science.

In this study, we present a novel method for fabricating semi-transparent electrodes by combining silver nanowires (AgNW) with titanium nitride (TiN) layers, resulting in conductive nanocomposite coatings with exceptional electromechanical properties. These nanocomposites were deposited on cellulose nanopaper (CNP) using a plasma-enhanced pulsed laser deposition (PE-PLD) technique at low temperatures (below 200 °C). Repetitive bending tests demonstrate that incorporating AgNW into TiN coatings significantly enhances the microstructure, increasing the electrode’s electromechanical robustness by up to four orders of magnitude compared to commercial PET/ITO substrates. Furthermore, the optical and electrical conductivities can be optimized by adjusting the AgNW network density and TiN synthesis temperature. Our results also indicate that the nanocomposite electrodes exhibit improved stability in air and superior adhesion compared to bare AgNW coatings.

A single-shot non-interferometric ultrashort-pulse measurement method based on the dispersion scan (d-scan) technique with a substantially extended time span for the pulses to be measured is presented. While single-shot d-scan is typically used for rather short femtosecond pulses, the presented multiple-reflections d-scan (MR d-scan) technique allows measurement of both short and long femtosecond pulses. Single-shot d-scan is currently limited to pulses with a maximum duration of 60 fs using a chromatic dispersion, i.e., a group delay dispersion (GDD) of 4400 fs2 at 840 nm provided by customized random nonlinear crystals. MR d-scan achieves a GDD of 31100 fs2 at 820 nm in this work, but can generally achieve an increase in GDD of up to two orders of magnitude. MR d-scan works with commonly available output couplers, does not rely on a homogeneous, precisely imaged beam profile and has an in-line configuration. As an example, long femtosecond double pulses are measured and reconstructed.

It is shown how to efficiently convert solar into electrical energy, taking advantage of laser amplification and intra-cavity use of a low-efficiency converter. The latter may consist of a low-efficiency transparent photovoltaic cell or a thermoelectric cell integrated into a metallic laser-cavity mirror, constituting a minor intra-cavity loss for the laser operation. The overall power conversion efficiency is derived and discussed for a variety of current solid-state laser materials. It is shown that power conversion efficiencies comparable with commercial silicon photovoltaic cells are obtained with current standard laser materials.

CuFeO2 and CuAlO2 are attractive candidate materials for solar energy harvesting applications such as photocatalysis and photovoltaics. This work describes the structural, optoelectronic, thermal and electric properties of alloyed CuAlxFe1-xO2 Delafossite material synthesized using solid-state sintering techniques. The alloyed samples of CuAlxFe1-xO2 Delafossite oxide consisted of substitution of Fe for Al ranging from x = 0.01 to x = 0.99. The inclusion of Al in low concentrations affects the crystallization rate during solid-state synthesis, dramatically changing the resultant sample morphologies. The addition of dilute amounts of Al also greatly improves the conductivity of the material to a maximum of 3.18 Scm(-1). The material absorption edge shows strong changes over the alloying range. The more highly conducting samples show a strong photoinduced thermoelectric response to Vis-NIR illumination. (C) 2020 Published by Elsevier B.V.

Metal oxide ceramics find widespread use as catalytic/photo-catalytic materials for a vast range of chemical reactions. For water-based reactions, hydroxylization, a process connected to the wettability of the surface, can greatly influence catalytic activity of a metal oxide. We present an investigation of the wetting properties of CuFeO2 delafossite oxide synthesized using hydrothermal methods. The material displayed significant variance in wetting properties, from highly hydrophobic for the as-grown powder, to complete wetting for porous cold-pressed pellets. A series of annealing treatments was performed to remove adsorbed functional groups. After annealing treatment at relatively low temperatures T > 300 degrees C (T-melt similar to 1100 degrees C), the CuFeO2 surface displayed superhydrophilicity and a rapid absorption of H2O droplets via its intergranular porosity. (C) 2019 Elsevier B.V. All rights reserved.

Delafossite CuFeO2 oxides were grown inside a hydrothermal reactor using Cu2O and FeOOH as precursors and NaOH as mineralizer. During this work the effect of the NaOH mineralizer and the reaction atmosphere was studied by varying the amount of NaOH used in the hydrothermal synthesis and by changing the reactor atmosphere from room air to high purity nitrogen. The oxides obtained were analyzed with Raman Spectroscopy, Fourier Transform Infrared Spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray Photoelectron spectroscopy (XPS), Field Emission Scanning Electron Microscopy (FESEM) and Energy Dispersive X-ray Spectroscopy (EDS), in order to obtain their morphological, chemical and structural characteristics. It was found that increasing the amount of mineralizer from 0.4 g up to 1.02 g improves considerably the hydrothermal reaction efficiency obtaining a resulting oxide with 93% of 3R-CuFeO2 phase and a subsequent decrease of the 2H-CuFeO2 phase. Moreover, using the same hydrothermal route it was shown possible to obtain high purity CuFeO2 compounds using small amounts of NaOH (0.4 g) if the reaction is performed under a non-oxidative atmosphere injecting pure nitrogen gas to the hydrothermal reactor where an increase of 3R-CuFeO2 phase from 36% to 94% was obtained. Finally, direct band gap of the semiconducting oxides were estimated using Tauc method from UV-vis spectra obtained by Diffuse Reflectance spectroscopy.

The photoconductivity within a wavelength range of 450–1100 nm was determined for a sample of epitaxial delafossite CuFeO 2 film grown by pulsed laser deposition. The film thickness was estimated to be 75 nm. The resistance of the films was determined with four-contact van der Pauw’s method and using monochromatic illumination of the film. The most significant change in resistance resulted in three rapid lineal conductivity increases at photon energies of ~ 1.5 eV (gap-1), ~ 2.1 eV (gap-2) and ~ 2.5 eV (gap-3). The conductivity properties are well correlated with prior optical absorption results obtained in the NIR-VIS region using transmittance spectroscopy.

It is shown how the efficiency limit of a photovoltaic cell can be overcome by placing it within the cavity of a solar-pumped co-doped Nd:YAG laser. The power conversion efficiency, among other aspects, is discussed.

A solar-pumped Nd:Cr:YAG ceramic laser is presented that is pumped by Fresnel lens sunlight concentrators via polymer optical fibers. Focusing into the laser medium via aspheric lenses allows to improve the laser beam quality.

We demonstrate a passively mode-locked Nd:Cr:YAG laser which is solar-pumped by optical fibers. With the achievement of a higher beam quality a semiconductor saturable absorber mirror can be used to generate picosecond pulses.

We discuss an analytical approach to spectral phase reconstruction from spectrographic measurements of ultrashort pulses. Pulses are reconstructed directly from two different spectrograms by implementing an element with quadratic dispersion over a wide spectral range.

We analyse the phase space representation of the optimal measurement of a phase shift in an interferometer with equal photon loss in both its arms. In the local phase estimation scenario with a fixed number of photons, we identify features of the spin Wigner function that warrant sub-shot-noise precision, and discuss their sensitivity to losses. We derive the asymptotic form of an integral kernel describing the process of photon loss in the phase space in the limit of large photon numbers. The analytic form of this kernel allows one to assess the ultimate precision limit for a lossy interferometer. We also provide a general lower bound on the quantum Fisher information in terms of spin Wigner functions.

We report a spectrographic technique for amplitude and phase measurements of ultrashort laser pulses (above 10 fs). Pulse information is obtained directly from two different spectrograms, using the mathematical relations between Wigner–Ville function projections. Pulses are reconstructed rapidly and unambiguously without stagnation. This non-interferometric method is demonstrated experimentally for the successful characterization of 100 fs pulses.

We reveal that quadrature squeezing can result in significantly better quantum-estimation performance with quantum heterodyne detection (of H. P. Yuen and J. H. Shapiro) as compared to quantum homodyne detection for Gaussian states, which touches an important aspect in the foundational understanding of these two schemes. Taking single-mode Gaussian states as examples, we show analytically that the competition between the errors incurred during tomogram processing in homodyne detection and the Arthurs-Kelly uncertainties arising from simultaneous incompatible quadrature measurements in heterodyne detection can often lead to the latter giving more accurate estimates. This observation is also partly a manifestation of a fundamental relationship between the respective data uncertainties for the two schemes. In this sense, quadrature squeezing can be used to overcome intrinsic quantum-measurement uncertainties in heterodyne detection.

A semi-classical analysis of the quantum rigid-rotor motion based on a phase-space description of the rotation in terms of a SO(3) covariant Wigner-like distribution is presented. The results are applied to the description of the intense-field alignment of an anisotropically polarizable molecule with high rotational excitation.

We investigate the dynamics of classical and quantum correlations between two qubits. Each qubit is implemented by a pair of phosphorous impurities embedded in a silicon substrate. The main decoherence mechanism affecting these types of qubits is provided by the coupling of the phosphorous impurities to the acoustical vibrations of the silicon lattice. We find that depending on the temperature of the substrate and the initial state, three different dynamics can be found. These are characterized by the number of abrupt changes in both classical and quantum correlations. We also show that the correlations do not disappear. Moreover, before the classical correlations reach a constant value, they may experience successive abrupt changes associated with the apparition of a metastable pointer-states basis. Then a constant value for the classical correlations is reached when the preferred basis is established.