Thermal lensing characterization of a high-radiance 946nm planar waveguide laser

We present the characterization of the in-plane thermal lens in a quasi-four-level Nd:YAG planar waveguide (PW) laser configured for high-radiance operation with an external stable-cavity. Our approach utilises the measurement of the laser's output irradiance distribution at the near- and far-field positions concurrently in order to obtain the "real time" beam propagation parameter and thus beam quality factor, M2. Coupled with the knowledge of the intra-cavity-thermal-lens- dependent beam sizes at an intra-cavity beam waist, the power dependent effective thermal lens focal length was characterized. A thermal lens focal length of >450 mm was obtained at all incident pump powers up to the maximum level of 87 W. This characterization enabled the build of a 29 W 946 nm PW laser with a record output radiance of 4.3 TWm-2sr-1

Availability and utilisation of physician-based pre-hospital critical care support to the NHS ambulance service in England, Wales and Northern Ireland

Background: Every day throughout the UK, ambulance services seek medical assistance in providing critically ill or injured patients with pre-hospital care. Objective: To identify the current availability and utilisation of physician-based pre-hospital critical care capability across England, Wales and Northern Ireland. Design: A postal and telephone survey was undertaken between April and December 2009 of all 13 regional NHS ambulance services, 17 air ambulance charities, 34 organisations affiliated to the British Association for Immediate Care and 215 type 1 emergency departments in England, Wales and Northern Ireland. The survey focused on the availability and use of physician-basedpre-hospital critical care support. Results: The response rate was 100%. Although nine NHS ambulance services recorded physician attendance at 6155 incidents, few could quantify doctor availability and utilisation. All but one of the British Association for Immediate Care organisations deployed ‘only when available’ and only 45% of active doctors could provide critical care support. Eleven air ambulance services (65%) operated with a doctor but only 5 (29%) operated 7 days a week. Fifty-nine EDs (27%) had a pre-hospital team but only 5 (2%) had 24 h deployable critical care capability and none were used regularly. Conclusion: There is wide geographical and diurnal variability in availability and utilisation of physician-based pre-hospital critical care support. Only London ambulance service has access to NHS-commissioned 24 h physician-based pre-hospital critical care support. Throughout the rest of the UK, extensive use is made of volunteer doctors and charity sector providers of varying availability and capability

Magnetic ordering in Sr2RuO4 induced by nonmagnetic impurities

We report unusual effects of nonmagnetic impurities on the spin-triplet superconductor Sr2RuO4. The substitution of nonmagnetic Ti4+ for Ru4+ induces localized-moment magnetism characterized by unexpected Ising anisotropy with the easy axis along the interlayer c direction. Furthermore, for x(Ti) > 0.03 magnetic ordering occurs in the metallic state with the remnant magnetization along the c-axis. We argue that the localized moments are induced in the Ru4+ and/or oxygen ions surrounding Ti4+ and that the ordering is due to their interaction mediated by itinerant Ru-4d electrons with strong spin fluctuations.Comment: 5 pages, 4figure

Phenomenology of the superconducting state in Sr2RuO4

The symmetry of the superconducting phase of Sr2RuO4 is identified as the odd-parity pairing state d(k)=\hat{z}(k_x \pm i k_y) based on recent experiments. The experimental evidence for the so-called orbital dependent superconductivity leads to a single-band description of superconductivity based on spin fluctuation mechanism. It is shown that the state \hat{z}(k_x \pm i k_y) can be stabilized by the spin fluctuation feedback mechanism analogous to the A-phase in 3He and by spin-orbit coupling effects.Comment: 7 pages, 1 figure, to be published in Proc. of the conference "Anomalous Complex Superconductors" (Crete, 1998

Anisotropy in the Antiferromagnetic Spin Fluctuations of Sr2RuO4

It has been proposed that Sr_2RuO_4 exhibits spin triplet superconductivity mediated by ferromagnetic fluctuations. So far neutron scattering experiments have failed to detect any clear evidence of ferromagnetic spin fluctuations but, instead, this type of experiments has been successful in confirming the existence of incommensurate spin fluctuations near q=(1/3 1/3 0). For this reason there have been many efforts to associate the contributions of such incommensurate fluctuations to the mechanism of its superconductivity. Our unpolarized inelastic neutron scattering measurements revealed that these incommensurate spin fluctuations possess c-axis anisotropy with an anisotropic factor \chi''_{c}/\chi''_{a,b} of \sim 2.8. This result is consistent with some theoretical ideas that the incommensurate spin fluctuations with a c-axis anisotropy can be a origin of p-wave superconductivity of this material.Comment: 5 pages, 3 figures; accepted for publication in PR

Effect of Spin-Orbit Interaction in Spin-Triplet Superconductor: Structure of d{\bf d}-vector and Anomalous 17^{17}O-NQR Relaxation in Sr2_2RuO4_4

Supposing the spin-triplet superconducting state of Sr$_2$RuO$_4$, the spin-orbit (SO) coupling associated with relative motion in Cooper pairs is calculated by extending the method for the dipole-dipole coupling given by Leggett in the superfluid $^{3}$He. It is shown that the SO coupling works only in the equal-spin pairing (ESP) state to make the pair angular momentum $\hbar{\vec L}$ and the pair spin angular momentum ${\rm i}{\vec d}\times{\vec d}^{*}$ parallel with each other. The SO coupling gives rise to the internal Josephson effect in a chiral ESP state as in superfluid A-phase of $^3$He with a help of an additional anisotropy arising from SO coupling of atomic origin which works to direct the {\bf d}-vector into $ab$-plane. This resolves the problem of the anomalous relaxation of $^{17}$O-NQR and the structure of {\bf d}-vector in Sr$_2$RuO$_4$.Comment: Accepted for publication in J. Phys. Soc. Jpn. vol.79 (2010), No.2 (February issue); 18 pages, 2 figure

Infrared properties of exotic superconductors

The infrared spectra of the non-traditional superconductors share certain common features. The lack of a gap signature at $2\Delta$ and the residual conductivity are the consequence of a d-wave order parameter. The high $T_c$ materials, the organic conductors and the heavy Fermion materials have a strong mid-infrared absorption band which can be interpreted as strong coupling of the carriers to electronic degrees of freedom which leads to a breakdown of the Fermi liquid picture. The cuprates and the organic charge transfer salts are unique in possessing an intrinsic low dimensionality. The charge transport normal to the highly conducting direction is incoherent down to the lowest temperatures and frequencies.Comment: 10 pages 11 figures, From the proceedings of the First Euroconference on Anomalous Complex Superconductors, Heraklion, Crete. Sept 1998, to be published in Physica

Vortex structure in chiral p-wave superconductors

We investigate the vortex structure in chiral p-wave superconductors by the Bogoliubov-de Gennes theory on a tight-binding model. We calculate the spatial structure of the pair potential and electronic state around a vortex, including the anisotropy of the Fermi surface and superconducting gap structure. The differences of the vortex structure between $\sin p_x + {\rm i} \sin p_y$-wave and $\sin p_x - {\rm i} \sin p_y$-wave superconductors are clarified in the vortex lattice state. We also discuss the winding $\mp 3$ case of the $\sin{(p_x+p_y)} \pm {\rm i} \sin{(-p_x+p_y)}$-wave superconductivity.Comment: 10 pages, 8 figure