We present the results of numerical calculations of the channelling and undulator radiation generated by an ultra-relativistic positron channelling along a crystal plane, which is periodically bent. The bending might be due either to the propagation of a transverse acoustic wave through the crystal, or due to the static strain as it occurs in superlattices. The periodically bent crystal serves ...

This paper discusses the undulator radiation emitted by high-energy positrons during planar channeling in periodically bent crystals. We demonstrate that the construction of the undulator for positrons with energies of 10 GeV and above is only possible if one takes into account the radiative energy losses. The frequency of the undulator radiation depends on the energy of the particle. Thus the ...

We reported the first observation of the two-photon-induced quantum cutting phenomenon in a Gd(3+)/Tb(3+)-codoped glass in which two photons at ~400 nm are simultaneously absorbed, leading to the cascade emission of three photons in the visible spectral region. The two-photon absorption induced by femtosecond laser pulses allows the excitation of the energy states in Gd(3+) which are inactive f...

Emission spectra of avalanching n(+)p junctions manufactured in a standard CMOS technology with no process modifications were measured over a broad photon energy spectrum ranging from 0.8 eV to 2.8 eV at various temperatures. The temperature coefficients of the emission rates at different photon energies were determined. Below a photon energy of 1.35 eV the temperature coefficient of emission w...

Gated photon counting spectroscopy and species-resolved ICCD photography have been applied to study the weak plasma luminescence which occurs following the propagation of the initial ablation plume in vacuum and during the 'rebound' of the plume with a substrate during pulsed laser deposition of amorphous diamond. These timeand spatially-resolved spectroscopic techniques were required in order ...

We report on the experimental observation of bright photoluminescence emission at room temperature from single unstrained GaAs quantum dots (QDs). The linewidth of a single-QD ground-state emission (% 8.5 meV) is comparable to the ensemble inhomogeneous broadening (% 12.4 meV). At low temperature (T £ 40 K) photon correlation measurements under continuous wave excitation show nearly perfect sin...

Recent simulations show that very large electric and magnetic fields near the kilo Tesla strength will likely be generated by ultra-intense lasers at existing facilities over distances of hundreds microns in underdense plasmas. Stronger ones are even expected future although some technical dificulties must overcome. In addition, it has been shown vacuum exhibits a peculiar non-linear behaviour ...

(S3) Measurement of two-photon cross section. (S3) Cytotoxicity assay. (S3) Cell culture. (S4) Two-photon and one-photon fluorescence bioimaging. (S4) Calculation of mean fluorescence intensity (S4) Table S1. Absorption and emission maxima of 1a~1c in DMSO. (S4) Table S2. Absorption and emission maxima of 1c in various solvents. (S10) Fig. S10. 2P microscopy of 2a-labeled HeLa cells for biothio...

The concept of stimulated emission of bosons has played an important role in modern science and technology, and constitutes the working principle for lasers. In a stimulated emission process, an incoming photon enhances the probability that an excited atomic state will transition to a lower energy state and generate a second photon of the same energy. It is expected, but not experimentally show...

BACKGROUND Patients with coronary artery disease can accumulate significant radiation dose through repeated exposures to coronary computed tomographic angiography, myocardial perfusion imaging with single photon emission computed tomography or positron emission tomography, and to invasive coronary angiography. Aim of the study was to audit radiation doses of coronary computed tomographic angiog...