11Metal nanoclusters consist of a few to few hundreds of atoms, and exhibit attractive molecular 12 properties such as ultrasmall size, discrete energy levels and strong fluorescence. Although 13 patterning of these clusters down to the microscale or nanoscale could lead to 14 applications such as high-density data storage, it has been reported only for inorganic 15matrices. Here we demonstrate the first submicron-scale mask-free patterning of fluorescent 16 silver nanoclusters in an organic matrix. The nanoclusters were produced by direct 17 laser writing in poly(methacrylic acid) thin films, and exhibit a broadband emission at visible 18 wavelengths with photostability that is superior to Rhodamine 6G dye. This fabrication 19 method could open new opportunities for applications in nanophotonics like imaging, 20 labeling, and metal ion sensing. We foresee that this method can be further applied to prepare 21 other metal nanoclusters embedded in compositionally different polymer matrices. 22 KEYWORDS 24Optical lithography, metal nanoclusters, photoluminescence, photobleaching, photostability, 25 polymer 26

Positron annihilation spectroscopy was used to study GaAsN/GaAs epilayers. GaAsN layers were found to contain Ga vacancies in defect complexes. The density of the vacancy complexes increases rapidly to the order of 10 18 cm Ϫ3 with increasing N composition and decreases after annealing at 700°C. The anticorrelation of the vacancy concentration and the integrated photoluminescence intensity suggests that the Ga vacancy complexes act as nonradiative recombination centers.

A central research area in nonlinear science is the study of instabilities that drive extreme events. Unfortunately, techniques for measuring such phenomena often provide only partial characterisation. For example, real-time studies of instabilities in nonlinear optics frequently use only spectral data, limiting knowledge of associated temporal properties. Here, we show how machine learning can overcome this restriction to study time-domain properties of optical fibre modulation instability based only on spectral intensity measurements. Specifically, a supervised neural network is trained to correlate the spectral and temporal properties of modulation instability using simulations, and then applied to analyse high dynamic range experimental spectra to yield the probability distribution for the highest temporal peaks in the instability field. We also use unsupervised learning to classify noisy modulation instability spectra into subsets associated with distinct temporal dynamic structures. These results open novel perspectives in all systems exhibiting instability where direct time-domain observations are difficult.

A quantitative and simultaneous measurement of K, KCl, and KOH vapors from a burning fuel sample combusted in a single particle reactor was performed using collinear photofragmentation and atomic absorption spectroscopy (CPFAAS) with a time resolution of 0.2 s. The previously presented CPFAAS technique was extended in this work to cover two consecutive fragmentation pulses for the photofragmentation of KCl and KOH. The spectral overlapping of the fragmentation spectra of KCl and KOH is discussed, and a linear equation system for the correction of the spectral interference is introduced. The detection limits for KCl, KOH, and K with the presented measurement arrangement and with 1 cm sample length were 0.5, 0.1, and 0.001 parts per million, respectively. The experimental setup was applied to analyze K, KCl, and KOH release from 10 mg spruce bark samples combusted at the temperatures of 850, 950, and 1050 °C with 10% of O2. The combustion experiments provided data on the form of K vapors and their release during different combustion phases and at different temperatures. The measured release histories agreed with earlier studies of K release. The simultaneous direct measurement of atomic K, KCl, and KOH will help in the impact of both the form of K in the biomass and fuel variables, such as particle size, on the release of K from biomass fuels.

An ultrasonic particle concentrator based on a standing-wave hemispherical resonator is combined with confocal laser-scanning fluorescence detection. The goal is to perform ultrasensitive biomedical analysis by concentration of biologically active microspheres. The standing-wave resonator consists of a 4 MHz focusing ultrasonic transducer combined with the optically transparent plastic bottom of a disposable 96-well microplate platform. The ultrasonic particle concentrator collects suspended microspheres into dense, single-layer aggregates at well-defined positions in the sample vessel of the microplate, and the fluorescence from the aggregates is detected by the confocal laser-scanning system. The biochemical properties of the system are investigated using a microsphere-based human thyroid stimulating hormone assay.

We demonstrate incoherent broadband cavity enhanced absorption spectroscopy in the mid-infrared wavelength range from 3000 to 3450 nm using an all-fiber based supercontinuum source. Multi-components gas detection is performed and concentrations of acetylene and methane are retrieved with sub-ppm accuracy. A linear response to nominal gas concentrations is observed demonstrating the feasibility of the method for sensing applications.PACS numbers: 42.81.Dp, 42.68.Ca, 42.62.Fi, 42.72.Ai Keywords: Spectroscopy, Supercontinuum, mid-infrared Gas detection and accurate concentration measurements are important in many fields ranging from industrial process to emission control and pollution monitoring. Different spectroscopic methods have been developed to retrieve gas concentrations with very high accuracy including cavity ring down spectroscopy 1,2 and its broadband implementation 3 , integrated cavity output spectroscopy 4 , noise-immune cavity-enhanced optical-heterodyne molecular spectroscopy 5 , or cavity enhanced absorption spectroscopy (CEAS) 6,7 . Each of these methods presents advantages and drawbacks in terms of sensitivity, selectivity, footprint and cost.Cavity enhanced absorption spectroscopy is conceptually relatively simple and a robust experimental setup can be implemented from off-the-shelf components. In CEAS, one uses a highly reflective cavity to increase significantly the optical path and thus the interaction length between the light beam and gas molecules, which leads to enhanced sensitivity. However, because of the mirrors highly reflectivity, the light intensity at the cavity output is dramatically reduced such that a detector with high sensitivity is generally required to measure the absorption. CEAS can be selective for a particular gas absorption line if a source with narrow linewidth is used, or it can also perform multi-components detection when a light source with a broad spectrum is employed.The recent development of light sources operating in the mid-infrared has recently allowed to extend precise spectroscopic measurements to the molecular fingerprint region where many gases posses strong absorption lines, and indeed several studies have reported measurements from pure gas in the 3-5 microns region [8][9][10][11][12] . All these recent studies used optical parametric oscillators based on difference-frequency generation or a quantum cascade laser. Whilst some of the recent demonstrations allow for extreme sensitivity, the light source is single specie specific, which may limit the usability. The development of broadband supercontinuum sources 13 on the other hand, has revolutionized many applications ranging from frequency metrology to imaging and spectroscopy. Taking advantage of the high spatial coherence and high brightness of this type of source we demonstrate multi-components gas detection in the mid-infrared over a bandwidth as large as 450 nm using incoherent broadband cavity enhanced absorption spectroscopy. These results are significant not only because they illustrate the poten...

Although luminescence of water during irradiations of proton and carbon-ion lower energy than the Cerenkov-light threshold were found recently, the sources of the luminescence were not yet obvious.To estimate the sources of the luminescence, we measured the light spectrum of the luminescence of water during carbon-ion irradiations and estimated the sources of the luminescence. Using an ultraviolet (UV) light sensitive charge coupled device (CCD) camera, we measured the luminescence images of water during carbon-ion beam irradiations by changing optical filters, derived the light spectra of the luminescence of water and compared with the calculated results. The intensity of the measured light spectrum of the luminescence of water at the Bragg peak region was decreased as the wavelength of light proportional to ∼λ −2.0 where λ is the wavelength of the light, indicating the source of the luminescence of water can be electromagnetic pulse produced by the dipole displacement inside the water molecules. In the shallow part of the water prior to the Bragg peak, where the Cerenkov-light is included, the spectrum showed steeper curve that is proportional to ∼λ −2.6 , which was similar to the calculated spectrum of Cerenkov-light including the refractive index changes of water with the wavelength of light. From these results, the luminescence of water is thought to be mainly come from electromagnetic pulse produced by the dipole displacement inside the water molecules.

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