Abstract
Fiber Bragg gratings (FBGs) are today fundamental components in fiber optics. They can be used as sensors, in signal processing, e.g. telecom applications, as wavelength stabilizers in fiber lasers or in dispersion compensators. However, there are applications where the demand for fiber Bragg gratings is not compatible with standard photosensitivity techniques like germanium doping or hydrogen loading. Examples are their use as laser-mirrors in spliceless all fiber fiber-laser solutions or the fiber Bragg grating inscription in suspended core all silica fibers for evanescent field sensing. Fiber Bragg grating inscription with femtosecond-laser exposure is a challenging new method to realize grating structures for waveguides made of materials which do not provide UV-photosensitivity. Especially fs-IR-inscription has been demonstrated for Bragg grating inscription in a variety of material systems such as boron-silica glass, sapphire and pure silica glass. The feasibility of the phase mask FBG inscription technique with DUV femtosecond lasers was also shown, which allows grating inscription even in pure silica microstructured fibers. The phase mask inscription method requires that the fiber will be placed directly behind the phase mask. While the laser beam should be focused onto the fiber to support nonlinear material interaction, this inscription method also leads to phase mask degradations, presumably due to non-bridging oxygen holes (NBOH). Our solution to avoid the mask degradation is to increase the space between fiber and phase mask by using a Talbot-interferometer. Another advantage is the wavelength versatility of this inscription setup. Due to the short temporal coherence length of the femtosecond pulses, the angular alignment variability of the interferometer mirrors is limited and restrictions concerning the wavelength versatility of the interferometer arise. Grating arrays in pure silica suspended core fibers are demonstrated as an example for the versatility of the inscription arrangement. © 2009 SPIE.

Abstract
Chick embryos are among the most studied species in development biology because they are easily obtained, highly accessible and present a similar development to that of humans. Normally morphological studies are carried out with confocal microscopy, however in-situ imaging is impossible and in-vivo imaging can only be performed with great difficulty. For confocal microscopy the embryo has to be studied outside the egg, what generally also means a short life expectancy of the embryo. Additionally, extracting the embryo of the egg precludes the possibility of studying its development in its natural environment. In this paper it is shown that en-face optical coherence tomography (en-face OCT) is a possible solution to overcome these difficulties allowing for an in-situ and in-vivo study over a timescale of several days. With en-face OCT it is possible to accompany the development of one single embryo over several days and to acquire high resolution and axially resolved images. © 2009 SPIE-OSA.

Abstract
We discuss and compare several concepts of optical cryptographic systems currently being proposed to improve communication security, their strong points and weaknesses. We will focus on approaches based on chaos synchronization.

Abstract
It has been suggested that dark matter particles which scatter inelastically from detector target nuclei could explain the apparent incompatibility of the DAMA modulation signal (interpreted as evidence for particle dark matter) with the null results from CDMS-II and XENON10. Among the predictions of inelastically interacting dark matter are a suppression of low-energy events, and a population of nuclear recoil events at higher nuclear recoil equivalent energies. This is in stark contrast to the well-known expectation of a falling exponential spectrum for the case of elastic interactions. We present a new analysis of XENON10 dark matter search data extending to E(nr)=75 keV nuclear recoil equivalent energy. Our results exclude a significant region of previously allowed parameter space in the model of inelastically interacting dark matter. In particular, it is found that dark matter particle masses m(chi)greater than or similar to 150 GeV are disfavored.

Abstract
Experimental measurements of the extraction efficiency f of the UV-induced photoelectrons emitted from a CsI photocathode into gas mixtures of Ne with CH4, CF4, CO2 and N-2 are presented; they are compared with model-simulation results. Backscattering of low-energy photoelectrons emitted into noble gas is significantly reduced by the admixture of molecular gases, with direct impact on the effective quantum efficiency. Data are provided on the dependence of f on the type and concentration of the molecular gas in the mixtures and on the electric field.

Abstract
XENON10 is an experiment designed to directly detect particle dark matter. It is a dual phase (liquid/gas) xenon time-projection chamber with 3D position imaging. Particle interactions generate a primary scintillation signal (S1) and ionization signal (S2), which are both functions of the deposited recoil energy and the incident particle type. We present a new precision measurement of the relative scintillation yield L(eff) and the absolute ionization yield 2, for nuclear recoils in xenon. A dark matter particle is expected to deposit energy by scattering from a xenon nucleus. Knowledge of L(eff) is therefore crucial for establishing the energy threshold of the experiment; this in turn determines the sensitivity to particle dark matter. Our L(eff) measurement is in agreement with recent theoretical predictions above 15 keV nuclear recoil energy, and the energy threshold of the measurement is similar to 4 keV. A knowledge of the ionization yield 2(y) is necessary to establish the trigger threshold of the experiment. The ionization yield 2(y) is measured in two ways, both in agreement with previous measurements and with a factor of 10 lower energy threshold.