Radiation loss of photonic crystal coupled-cavity waveguides

We experimentally investigate the out-of-plane radiation losses of photonic crystal coupled-cavity waveguides. We observe a strong variation in the losses along the dispersion curve and show that such variation is closely linked with the specific far-field radiation pattern of a single cavity constituent. A simple theoretical model based on tight-binding approximation is used to describe this behavior

Highly Selective Volatile Organic Compounds Breath Analysis Using a Broadly-Tunable Vertical-External-Cavity Surface-Emitting Laser.

A broadly tunable mid-infrared vertical-external-cavity surface-emitting laser (VECSEL) is employed in a direct absorption laser spectroscopic setup to measure breath acetone. The large wavelength coverage of more than 30 cm <sup>-1</sup> at 3.38 μm allows, in addition to acetone, the simultaneous measurement of isoprene, ethanol, methanol, methane, and water. Despite the severe spectral interferences from water and alcohols, an unambiguous determination of acetone is demonstrated with a precision of 13 ppbv that is achieved after 5 min averaging at typical breath mean acetone levels in synthetic gas samples mimicking human breath

Coupling length of silicon-on-insulator directional couplers probed by Fourier-space imaging

We use a Fourier-space imaging technique relying on outcoupling grating probes to study the coupled mode interaction and dispersion properties of guided modes in silicon-on-insulator codirectional couplers. Our approach allows us to measure the mode splitting inherent to coupled systems, determine the mode symmetry, and locally probe the coupling length with an accuracy of +/- 50 nm. A systematic study of directional couplers with different waveguide widths, coupling gaps, and e-beam exposure doses is reported in order to verify the results across a wider parameter space. (C) 2008 American Institute of Physics.</p

Integrated photonic materials for the mid-infrared

While silicon photonic integrated circuits for the near-infrared (IR) telecommunication band have attracted great research interest in the past decade, recent advances offer opportunities to extend the operational wavelength to the mid-IR (2.5-20 mu m) for free space communications, sensing, environmental monitoring and much more. In this study, we will comprehensively review the current status of materials available for mid-IR waveguides and waveguide integrated photodetectors, with a few application oriented examples to illustrate the technological importance and significant growth opportunity for integrated photonics in the mid-IR regime. However, this wavelength regime also presents new material design and fabrication challenges. Therefore, we will discuss the critical issues prior to commercialization and will briefly summarize the outlook on future research topics along with opportunities