Physics

  2010 JUL 20 - (VerticalNews.com) -- According to a study from Warsaw, Poland, "We analytically find an approximate Bloch-Messiah reduction of a noncollinear parametric amplifier pumped with a focused monochromatic beam. We consider type I phase matching."

  "The results are obtained using a perturbative expansion and scaled to the high-gain regime. They allow for a straightforward maximization of the signal gain and minimization of the parametric fluorescence noise. We find the fundamental mode of the amplifier, which is an elliptic Gaussian defining the optimal seed beam shape," wrote P. Migdal and colleagues, University of Warsaw ...read more

  2010 APR 27 - (VerticalNews.com) -- According to recent research from Wroclaw, Poland, "Spectroscopic and kinetics properties of Lu2SiO5:Dy3+ (LSO:Dy) single crystal with 1 and 5 at.% of activator were investigated. The polarised absorption and unpolarised emission spectra were measured at 10-300 K. Parameters characterising radiative relaxations of LSO:Dy were estimated by the Judd-Ofelt model."

  "The crystal-field energy structure was derived from low-temperature optical spectra exhibiting the presence of two non-equivalent Dy3+ sites. It was found that dysprosium ions in site 1 and in site 2 do not form isolated subsystems; these subsystems are coupled by an effective spectral energy migration process. The LSO:Dy crystal exhibits a strong luminescence in the visible. Strong ion-ion interactions were observed for LSO:Dy (5 at.%); luminescence decays are non-exponential and the macro-parameter of donor-acceptor interaction C (da) amounts to 5.3 (10(-52) m(6) s(-1)) and 7.8 (10(-52) m(6) s(-1)) at 10 and 300 K, respectively. Laser potential related to the F-4(9/2)- > H-6(13/2) yellow luminescence in Dy:LSO was assessed based on evaluation of the emission cross section values," wrote G. Dominiakdzik and colleagues, Polish Academy of Science ...read more

  2010 APR 27 - (VerticalNews.com) -- "We have developed an ultra-stable source in the deep ultraviolet, suitable to fulfil the interrogation requirements of a future fully-operational lattice clock based on neutral mercury. At the core of the system is a Fabry-P,rot cavity which is highly impervious to temperature and vibrational perturbations," scientists in Paris, France report.

  "The mirror substrate is made of fused silica in order to exploit the comparatively low thermal noise limits associated with this material. By stabilizing the frequency of a 1062.6 nm Yb-doped fiber laser to the cavity, and including an additional link to LNE-SYRTE's fountain primary frequency standards via an optical frequency comb, we produce a signal which is both stable at the 10(-15) level in fractional terms and referenced to primary frequency standards," wrote S.T. Dawkins and colleagues ...read more