Tunable coupled-cavity waveguide laser at room temperature in Nd-diffused Ti:LiNbO₃

We report on a Y-junction channel waveguide laser, operating at room temperature, in Nd-diffused Ti:LiNbO3. Pumping was performed with a cw Ti:Al2O3 laser operating at 816 nm. With feedback provided only by the polished end faces of the device, a cw lasing threshold of ~39-mW launched pump power was obtained, with a slope efficiency of ~35%. Using 95% reflectivity mirrors at the waveguide ends, we reduced the lasing threshold to ~4 mW, with a slope efficiency of ~2.6%. Tuning of the lasing signal over a range of 2.3 nm around a center wavelength of 1092.7 nm was demonstrated, with a monolithically integrated phase modulator

Neodymium-diffused tunable Y-branch waveguide laser in LiNbO₃ operating at room temperature

Rare-earth-doped waveguide optical lasers and amplifiers have received considerable attention in recent years, both in fibre form and as channel waveguides on planar substrates. Channel waveguide geometries lend themselves ideally for applications in active integrated circuits, with the potential for photolithographic definition of complex-cavity devices and monolithically integrated modulators for tuning, line-narrowing, Q-switching and mode-locking

Measurement of complex coupling coefficients of directional coupling by thermo-optic modulation

Directional coupling between two parallel singlemode optical waveguides is the functional principle underlying numerous integrated optical devices, such as modulators, filters and sensors. As the coupling efficiency depends critically on the synchronism of wave propagation and on the field overlap of the two guides, tight tolerances apply in waveguide fabrication, and a precise determination of the coupling parameters is essential

1.7 micron excited state absorption measurement in erbium-doped glasses

We have measured, for the first time, the complete 1.7µm excited state absorption spectrum in erbium doped glasses. The spectrum is obtained by measuring the gain of an erbium doped waveguide in the 1400-1800 nm region. Using the measured spectra, we estimate the 1.5µm uniform upconversion rate by calculating the spectral overlap between the 1.5µm emission and 1.7µm ESA cross sections. The technique is applied to erbium-doped, ion-exchangeable silicate glasses, yielding upconversion constants in the range of 1-10 x 10-18 cm3 /s

Diode-pumped, ion-exchanged Er/Yb waveguide laser at 1.5µm in phosphorus-free silicate glass

We demonstrate the first diode-pumped, planar ErNb waveguide laser. The device was fabricated by thallium-exchange in a phosphorus-free silicate glass. Lasing was achieved with a low threshold of 15 mW, indicating the absence of the severe backtransfer effects previously reported in Er/Yb bulk laser silicate glasses

Diode-pumped, planar lossless splitter at 1.5 microns for optical networks

We demonstrate the first planar lossless splitter at 1.5µm. The ion-exchanged waveguide circuit in Er/Yb codoped silicate glass achieved 1x2 lossless splitting at 1537nm with a 980 nm laser diode pump

Lossless integrated active splitters for optical networks

We discuss the latest results in the European Union RACE II project LIASON to specify and develop "lossless" splitters in integrated optics, combining an erbium-doped planar amplifier and a passive 1xN cascaded y-junction splitter

Probing Primordial Non-Gaussianity with Large-Scale Structure

We consider primordial non-Gaussianity due to quadratic corrections in the gravitational potential parametrized by a non-linear coupling parameter fnl. We study constraints on fnl from measurements of the galaxy bispectrum in redshift surveys. Using estimates for idealized survey geometries of the 2dF and SDSS surveys and realistic ones from SDSS mock catalogs, we show that it is possible to probe |fnl|~100, after marginalization over bias parameters. We apply our methods to the galaxy bispectrum measured from the PSCz survey, and obtain a 2sigma-constraint |fnl|< 1800. We estimate that an all sky redshift survey up to z~1 can probe |fnl|~1. We also consider the use of cluster abundance to constrain fnl and find that in order to be sensitive to |fnl|~100, cluster masses need to be determined with an accuracy of a few percent, assuming perfect knowledge of the mass function and cosmological parameters.Comment: 15 pages, 7 figure

The Java Context Awareness Framework (JCAF) – A Service Infrastructure and Programming Framework for Context-Aware Applications

Abstract. Context-awareness is a key concept in ubiquitous computing. But to avoid developing dedicated context-awareness sub-systems for specific applica-tion areas there is a need for more generic programming frameworks. Such frame-works can help the programmer to develop and deploy context-aware applications faster. This paper describes the Java Context-Awareness Framework – JCAF, which is a Java-based context-awareness infrastructure and programming API for creating context-aware computer applications. The paper presents the design principles behind JCAF, its runtime architecture, and its programming API. The paper presents some applications of using JCAF in three different applications and discusses lessons learned from using JCAF.

Ion-exchanged planar lossless splitter for analog CATV distribution systems at 1.5µm

We demonstrate for the first time an ion-exchanged, planar lossless splitter pumped at 980 nm in an analog CATV distribution system at 1.5 µm