Amplified spontaneous emission (laser action without cavities) from deoxyribonucleic acid (DNA) derivative films was achieved by doping with a hemicyanine dye which is well known as a nonlinear optical molecule. The amplification confirmed by spectral narrowing and superlinear dependence of the emission intensity on the pumping was observed from the complex films when the film samples were irradiated with a nanosecond laser at the intensity above a threshold value (∼20 μJ). The durability and low threshold values suggest the possibility of DNA complexes as a practical candidate for thin-film dye lasers.

We investigated the annealing effect on single Shockley faults (SSFs) in the SiC epitaxial layers by photoluminescence mapping in combination with high-power laser illumination. Comparing before and after annealing at 350–550°C, it became obvious that annealing results in the shrinking of the faulted area of SSFs. When high-power laser illumination is performed again on the same area annealed at 550°C, the right-angled triangular SSFs reformed into exactly the same features as those before annealing, but the isosceles triangular SSFs did not reform. The annealing temperature to start shrinking the faulted area differs according to the type of SSF.

Polyfluorenes are conjugated polymers that show strong blue emission and as such have been explored for potential applications in light-emitting devices. However, heat treatment, prolonged exposure to air, or extended operation in electroluminescent devices can lead to an appearance of parasitic green emission that degrades the material performance. This phenomenon has been extensively studied over the past two decades, and two main and conflicting explanations, i.e., oxidation and formation of fluorenone species on the one hand and inter-or intrachain aggregation on the other, have been put forward. There is abundant experimental evidence to support either of these theories, and the question is far from settled. Here, we aim at getting deeper insight into the problem of the green emission origin using single-molecule spectroscopy performed on individual chains of poly(9,9-di-n-octylfluorene) (PFO) to resolve the green emission band and reveal its spectral and temporal heterogeneity. We disperse single PFO chains in solid thin-film matrices of polystyrene (PS) and poly(methyl methacrylate), as well as in solutions of cyclohexane, toluene, or PS/toluene, to simulate good and poor-solvent environments and environments with different permeabilities and diffusions of oxygen, to systematically study the effects of intrachain aggregation as well as oxidation on the appearance and characteristics of the green band. The studies are complemented by direct measurement of individual chain conformation by atomic force microscopy and by bulk measurements of photoluminescence (PL) lifetimes and quantum yield. The single-molecule results reveal two PL spectral forms in the region of the green emission, a vibrationally resolved type located around 500 nm and broad structureless type located toward lower energies, none of them sensitive to the presence of oxygen. These two types are characterized by different lifetimes of 1.4 and 5.1 ns, respectively, and their oscillator strengths are 2 orders of magnitude smaller compared to those of the blue emission band. These results point to two different optical transitions comprising the green band, and these have been assigned to the emission of H-aggregates and charge transfer or indirectly excited excimer states, respectively.

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As blind patients with an intact optic nerve and damaged photoreceptor cells increase in number in recent years, there has been a growing interest in visual prostheses by electrically stimulating their retinas. Previous clinical studies indicated that blind patients perceive a controlled electrical current applied to a small area of the retina via electrodes as a spot of light. We propose a novel implantable device, so-called three-dimensionally (3D) stacked retinal prosthesis, which is composed of a photodetector, an image processor, electrical current generator circuits, and an electrode array on one chip. The spice simulation showed that our designed analog circuits for 3D stacked retinal prosthesis chip could output desirable electrical current with variable pulse width by controlling bias voltages.