Compatibility and Marginality

We present a way of introducing joint distibution function and its marginal distribution functions for non-compatible observables. Each such marginal distribution function has the property of commutativity. Models based on this approach can be used to better explain some classical phenomena in stochastic processes.     

Ionization penalty in nonlinear Raman neuroimaging

Light-assisted ionization accompanying coherent anti-Stokes Raman scattering (CARS) of ultrashort laser pulses in brain tissue is shown to manifest itself in a detectable blueshift of the anti-Stokes signal. This blueshift can serve as an indicator of ionization processes in CARS-based neuroimaging.     

Spectrally narrow, long-term stable optical frequency reference based on a Eu3+:Y2SiO5 crystal at cryogenic temperature

Using an ultrastable continuous-wave laser at 580 nm we performed spectral hole burning of Eu(3+):Y(2)SiO(5) at a very high spectral resolution. The essential parameters determining the usefulness as a macroscopic frequency reference, linewidth, temperature sensitivity, and long-term stability, were characterized using a H-maser stabilized frequency comb. Spectral holes with a linewidth as low as 6 kHz were observed and the upper limit of the drift of the hole frequency was determined to be 5±3 mHz/s. We discuss the necessary requirements for achieving ultrahigh stability in laser frequency stabilization to these spectral holes.     

Essential points of conformal vector fields

An essential point of a conformal vector field ξ$\xi$ on a conformal manifold (M,c)$(M,c)$ is a point around which the local flow of ξ$\xi$ preserves no metric in the conformal class c$c$. It is well-known that a conformal vector field vanishes at each essential point. In this note we show that essential points are isolated. This is a generalization to higher dimensions of the fact that the zeros of a holomorphic function are isolated. As an application, we show that every connected component of the zero set of a conformal vector field is totally umbilical.     

Non-linear applications of microstructured optical fibres

The enhancement of different non-linear processes in microstructured optical fibres can be achieved through manipulation of the dispersion characteristics of the fibre. This is demonstrated by extending the region of short wavelength operation of high power supercontinuum generation through four wave mixing in a cascaded fibre geometry where the dispersion of each fibre decreased on propagation. The technique is further refined in a demonstration utilizing long lengths of dispersion decreasing tapered microstructured fibres, where the supercontinuum extends to around 300 nm with spectral power densities in excess of 2 mW/nm in the uv. These long length tapers can also be utilized for adiabatic soliton pulse compression in new spectral regions, allowing the compression of 655 fs pulses to 45 fs.     

Effects of photon field on heat transport through a quantum wire attached to leads

We theoretically investigate photo-thermoelectric transport through a quantum wire in a photon cavity coupled to electron reservoirs with different temperatures. Our approach, based on a quantum master equation, allows us to investigate the influence of a quantized photon field on the heat current and thermoelectric transport in the system. We find that the heat current through the quantum wire is influenced by the photon field resulting in a negative heat current in certain cases. The characteristics of the transport are studied by tuning the ratio, $?{\omega }_{\gamma }/k_{\mathrm{B}}\mathrm{\Delta }T$, between the photon energy, $?{\omega }_{\gamma }$, and the thermal energy, $k_{\mathrm{B}}\mathrm{\Delta }T$. The thermoelectric transport is enhanced by the cavity photons when $k_{\mathrm{B}}\mathrm{\Delta }T>?{\omega }_{\gamma }$. By contrast, if $k_{\mathrm{B}}\mathrm{\Delta }T<?{\omega }_{\gamma }$, the photon field is dominant and a suppression in the thermoelectric transport can be found in the case when the cavity-photon field is close to a resonance with the two lowest one-electron states in the system. Our approach points to a new technique to amplify thermoelectric current in nano-devices.     

DTA and X-ray diffraction investigations of laser-irradiated CeO2 powders

The TG and DTA curves and diffractograms of powdered CeO₂ samples irradiated with a CO₂ laser beam with powers of 0.41–1.39 kW/cm² are presented. The laser treatment induced structural changes and probably generation of a metastable phase. X-ray diffraction coupled with thermal analysis was used to establish the structural modifications in the irradiated samples after heating.