Abstract
By measuring intensity distributions of cladding modes and using an optimization technique we show that the perturbation which forms arc-induced gratings in standard fibers is antisymmetric, while the perturbation in boron-germanium codoped fibers is symmetric. © 2006 Optical Society of America.

Abstract
The fabrication and characterization of long-period gratings (LPGs) in fiber tapers is presented alongside supporting theory. The devices possess a high sensitivity to the index of aqueous solutions due to an observed spectral bifurcation effect, yielding a limiting index resolution of +/- 8.5 x 10(-5) for solutions with an index in the range 1.330-1.335.

Abstract

Abstract
A versatile time-domain OCT system is presented which, for the first time, can generate cross-section images (B-scans) by using either transverse priority (T-scans) or depth priority (A-scans). Images from the optic nerve are obtained with either regime, with the same system. In different scanning regimes, different values are allowed for the maximum power to be launched to the eye. We present the maximum exposure level for a variety of scanning procedures, such as generation of cross section images and 3D volumes employing either A or T scanning.

Abstract
Third-order nonlinear and linear optical properties of nickel(II) and copper(II) complexes with salen ligands, functionalised with electron donor/acceptor groups (DA-salen), have been investigated in solution by the Z-scan technique using an Nd:YAG laser (lambda(inc) = 1064 nm) and UV/Vis spectroscopy. The [M(DA-salen)] complexes exhibit positive nonresonant nonlinear refractive indexes (net) in the range 27.0-8.50 center dot 10(-21) m(2)W(-1) and nonlinear absorption coefficients (a(2)(I)) within the range 1.80-26.0 center dot 10(-17) mW(-1). The latter values correspond to less than 10% of the overall magnitude of the third-order susceptibility, vertical bar chi(3)vertical bar, which is the result of the absence of electronic transitions near lambda(inc) = 1064 nm. For the group of N-II complexes, the highest net values are exhibited by the complexes with aromatic diimine bridges and large pi-electron delocalisation, which leads to intense electronic charge-transfer bands (epsilon > 16000 mol(-1) dm(3) cm(-1)) in the region lambda = 275-500 nm. The complexes that exhibit charge-transfer bands near lambda(inc)/2 = 532 nm, also show the highest a(2)(I) values, a consequence of multiphoton absorption processes. For the group of Cult complexes, the highest net value is also observed by the complex that exhibits the most intense charge-transfer bands in the region lambda = 275-475 nm. Between Ni-II and Cu-II complexes with the same DA-salen ligands, those of copper show always higher net values, indicating that NLO responses can also be fine-tuned by the metal centre. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Abstract
Can entanglement and the quantum behavior in physical systems survive at arbitrary high temperatures? In this Letter we show that this is the case for a electromagnetic field mode in an optical cavity with a movable mirror in a thermal state. We also identify two different dynamical regimes of generation of entanglement separated by a critical coupling strength.