Physical unclonable functions on carbon fiber reinforced polymers using laser techniques.

We have successfully fabricated physical unclonable functions (PUF)s on carbon fiber reinforced polymers (CFRP) in the form of computer-generated holograms (CGH)s using an industrial friendly UV ns laser system. The topological randomness of the fiber network and laser absorption yield laser engraved CGH that are unique. The engraved CGH serve as PUFs and this is confirmed by the exceptionally low values of probability of cloning (POC), lower than 10, well below the commonly accepted threshold value of 10 in the literature.

Experimental investigation and numerical modelling of photocurrent oscillations in lattice matched Ga1-xInxNyAs1-y/GaAs quantum well p-i-n photodiodes.

Photocurrent oscillations, observed at low temperatures in lattice-matched Ga1-xInxNyAs1-y/GaAs multiple quantum well (MQW) p-i-n samples, are investigated as a function of applied bias and excitation wavelength and are modelled with the aid of semiconductor simulation software. The oscillations appear only at low temperatures and have the highest amplitude when the optical excitation energy is in resonance with the GaInNAs bandgap. They are explained in terms of electron accumulation and the formation of high-field domains in the GaInNAs QWs as a result of the disparity between the photoexcited electron and hole escape rates from the QWs.

Low-temperature photoluminescence study of exciton recombination in bulk GaAsBi.

The exciton recombination processes in a series of elastically strained GaAsBi epilayers are investigated by means of time-integrated and time-resolved photoluminescence at T = 10 K. The bismuth content in the samples was adjusted from 1.16% to 3.

Optical gain in 1.3-μm electrically driven dilute nitride VCSOAs.

We report the observation of room-temperature optical gain at 1.3 μm in electrically driven dilute nitride vertical cavity semiconductor optical amplifiers. The gain is calculated with respect to injected power for samples with and without a confinement aperture.

Dilute nitride and GaAs n-i-p-i solar cells.

We demonstrate for the first time the operation of GaInNAs and GaAs n-i-p-i doping solar cells with ion-implanted selective contacts. Multiple layers of alternate doping are grown by molecular beam epitaxy to form the n-i-p-i structure. After growth, vertical selective contacts are fabricated by Mg and Si ion implantation, followed by rapid thermal annealing treatment and fabrication into circular mesa cells.

Photoconductivity and photoluminescence under bias in GaInNAs/GaAs MQW p-i-n structures.

The low temperature photoluminescence under bias (PLb) and the photoconductivity (PC) of a p-i-n GaInNAs/GaAs multiple quantum well sample have been investigated. Under optical excitation with photons of energy greater than the GaAs bandgap, PC and PLb results show a number of step-like increases when the sample is reverse biased. The nature of these steps, which depends upon the temperature, exciting wavelength and intensity and the number of quantum wells (QWs) in the device, is explained in terms of thermionic emission and negative charge accumulation due to the low confinement of holes in GaInNAs QWs.

GaInNAs-based Hellish-vertical cavity semiconductor optical amplifier for 1.3 μm operation.

Hot electron light emission and lasing in semiconductor heterostructure (Hellish) devices are surface emitters the operation of which is based on the longitudinal injection of electrons and holes in the active region. These devices can be designed to be used as vertical cavity surface emitting laser or, as in this study, as a vertical cavity semiconductor optical amplifier (VCSOA). This study investigates the prospects for a Hellish VCSOA based on GaInNAs/GaAs material for operation in the 1.

Non-resonant z-scan characterization of the third-order nonlinear optical properties of conjugated poly(thiophene azines).

The nonlinear optical properties of a functionalized poly(thiophene azine), namely, poly(3,4-didodecylthiophene azine), PAZ, at the optical telecommunication wavelength of 1550 nm are investigated by means of the closed-aperture z-scan technique in both thin films and solutions. Values of chi((3))=(2.4+/-0.

Two-photon absorption of Zn(II) octupolar molecules.

In this work we present an investigation of the non-linear optical (NLO) properties of two octupolar chromophores: [Zn(4,4'-bis(dibutylaminostyryl)-[2,2']-bipyridine)(3)](2+) and [Zn(4,4'-bis((E)-2-(N-(TEG)pyrrol-2-yl)vinyl)-[2,2']-bipyridine)(3)](2+) with Zn(ii) as the coordination center, using two-photon emission technique (TPE) in fs-pulse temporal regime. Compared to the free ligands, our results do not show a net increase in the two-photon absorption (TPA) cross-section for the octupolar complexes, once normalized to the ligand unit. This is in partial disagreement with a previous theoretical study investigating the first molecule where a significant increase of the TPA cross-section was predicted (X.