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PURPOSE A dual-energy (DE) phantom study was performed on two scanner types in order to evaluate (1) the stability and accuracy of CT numbers and iodine concentrations in function of object size; (2) the effect of beam hardening. METHOD AND MATERIALS Iodine concentrations of 3 and 6 mgI/ml were poured into two respective rows of cylindrical cavities with diameters ranging from 3 to 25.5 mm in an AAPM CT performance phantom. Besides this, a 16 mm diameter tube filled with 6 mgI/ml was placed in the main water-filled compartment, partly covered by a Teflon beam hardening ring. The phantom was scanned in standard 120 kVp and DE mode on a GE Healthcare Discovery HD750 and Siemens SOMATOM Definition Flash scanner at 3 CTDIvol's (9, 19 and 29 mGy). Iodine concentrations were determined for all cavities using the scanner's DE mode, and compared to their true concentrations. CT number stability was determined accordingly and a comparison was made between the DE acquisition and standard 120 kV scanning. RESULTS (1) Relatively constant (max VAR 14%) HU values for both scanners as a function of the object diameters were observed. The Siemens scanner showed a consistent overestimate of approximately 0.5 mgI/ml for both contrast concentrations. A significant decrease in concentration accuracy for object diameters smaller than 6 mm was present for both scanners. (2) A step-like increase of 10 HU upon transitioning out of the Teflon part was observed for both scanners at single energy 120 kV and the Siemens blended DE image, less for the GE DE image (AV 148 HU, max VAR 5 HU). CONCLUSION (1) Measured and true iodine concentrations were consistent down to 6 mm object size, notwithstanding an observed offset with one scanner type. (2) A step-like increase in HU highlights the effect of beam hardening, and is more prominent for classical scans compared to DE. CLINICAL RELEVANCE/APPLICATION DE CT techniques are being increasingly used in tumor imaging. Since iodine is a contrast agent commonly used in CT imaging, determining its detectable lower limit is a crucial factor. Iodine concentration estimations should be made with appropriate consideration.

We have investigated the label-free biosensing properties of grated silicon photonic wire (GSPW) waveguides with cross-sectional dimensions of 350 nm x 220 nm, fabricated using a 248-nm deep UV lithography process. The steep edges of the optical transmission spectrum of the GSPW enable detection of very small spectral shift, hence of small index changes. To obtain an antibody layer for the biosensing experiment, an immobilization process is required. We followed the standard immobilization process developed by Imenz B.V. The antibody immobilization process and the binding process of enzymes on an immobilized antibody layer have been monitored with the GSPW based sensor.

Multimode silicon-oxynitride (SiON) waveguide structures are investigated for probing fluorescence and backscattered light from samples of different thicknesses. The collection efficiency together with the resolution of such probes is compared to that of a conventional fiber probe. The simulation results show that, in case of low scattering samples, among the two types of probes the former present higher collection efficiencies when the sample thickness is below 85 µm. The analytical model developed to estimate the collection efficiency of the integrated probes was validated experimentally through fluorescence measurements carried out on a ruby rod. The model and the experimental results are both presented in this work.

Neodymium-doped Al2O3 layers were deposited on thermally oxidized Si substrates by reactive co-sputtering and channel waveguides were patterned using reactive-ion etching. Internal net gain on the Nd3+ transition at 1064 nm was experimentally investigated with various Nd3+ concentrations. With approximately 12 mW of launched pump power at 800 nm, a maximum gain of 4.0 dB/cm was demonstrated in a 1-cm-long Al2O3:Nd channel waveguide sample with a Nd3+ concentration of 1.68x1020 cm-3. Investigations of gain on the Nd3+ ground-state transition around 880 nm are under way. This wavelength range is of interest for amplification of signals transmitted through optical backplanes.

In this work plasma enhanced chemical vapor deposition (PECVD) were adopted to achieve boron/phosphorous (B/P) doped silicon oxynitride (SiON) layers. By adjusting the flow rates of corresponding gas precursor (PH3/Ar or B2H6/Ar), SiON layers with different B or P concentrations were obtained. Measurements by X-ray photoelectron spectroscopy (XPS) have shown that PH3 can result in more efficient doping in the layers than B2H6. Compared with B-doped samples, reduction of the hydrogen content can be more easily observed in P-doped SiON layers, as been confirmed by Fourier transform infrared spectroscopy. Hydrogen-related chemical bonds became undetectable after annealing of samples at temperatures as low as 700°C. These results are quite helpful to further research on B/P co-doped SiON layers in application of integrated optical waveguide devices.

Channel waveguides based on a polymer, 6-fluorinated-dianhydride/epoxy, which is actively doped with a rare-earth-ion-doped complex, Nd(thenoyltrifluoroacetone)3 1,10-phenanthroline, have been fabricated. Luminescence and loss spectra of the channel waveguides have been experimentally investigated. By optimization of the fabrication procedure of both, host material and optical structure, steady-state laser emission has been demonstrated from a channel waveguide near 1060 nm, which provides up to 440 µW of output power from the waveguide structures developed.

In this paper the design and modelling of an integrated Al2O3:Er3+ distributed feedback laser (DFB) is presented. The implemented laser model combines rate equations of the population mechanisms in the erbium ion with coupled-mode theory. The model enables the estimation of the optimum Bragg grating design that is required in order to realise such a DFB laser device. Based on the modelling results, the ideal grating geometry has been identified and fabricated by making use of laser interference lithography (LIL) and reactive ion etching (RIE). Optical characterisation experiments of the gratings are currently in progress.

High-quality crystalline KY(WO4)2:Yb3+ layers co-doped with large concentrations of optically inert Gd3+ and Lu3+ ions were grown by vertical liquid phase epitaxy. The codoping enhances the refractive index contrast between the active layer and the undoped KY(WO4)2 substrate to ~7.5×10-3. A K2W2O7 solvent was employed for the growth of layers onto undoped (010)-oriented KYW substrates. Single crystalline layers of thickness 5-10 µm were grown at low level of supersaturation and growth temperatures of 920-923°C. The layer quality was studied by X-ray diffraction. The composition of the grown layers was determined by laser-ablation inductively-coupled-plasma mass spectrometry (LA-ICP-MS). Planar waveguide lasers with low laser threshold of 18 mW, record-high slope efficiency of 82.3%, and maximum output power of 195 mW have been achieved.

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A study on a new ranging camera operating on the Time-of-Flight principle using 870nm active illumination is presented. The key component of this camera is a sensor comprised of 120x90 pixels based on a Current Assisted Photonic Demodulator (CAPD), implemented in standard CMOS 0.35um technology. The resulting camera system is capable of providing real-time accurate depth maps of the scene. An analysis was performed of the systematic noise of obtained depth map under various conditions. Measurement results with different modulation frequencies are presented showing non- linearities over the frequency range. In conclusion a compensation technique is proposed.

Dear Colleagues, With great pleasure we welcome you all to the 14th Annual Symposium of the IEEE Photonics Benelux Chapter in Brussels. The main fields of interest of the IEEE Photonics Society include lasers, integrated optics, optical fibres, optical communication systems and devices, optical sensors, physics of novel materials, nonlinear optics, quantum electronics, and quantum optics. The mission of the Benelux Chapter of the IEEE Photonics Society is the promotion of these research fields in the Benelux countries (Belgium, the Netherlands, and Luxembourg) by bringing together researchers and engineers working in universities, industry, and research institutes. Moreover, the IEEE Photonics Benelux Chapter increasingly promotes cross-border collaboration, also with scientists from adjacent regions in France and Germany. One of the platforms for triggering collaborations is provided by the Annual Symposium of the Chapter. Besides the oral lectures and poster presentations, it is an excellent opportunity for young researchers working towards their PhD, as well as for postdocs and senior researchers to have scientific discussions and exchanges with their peers, to build up and extend their regional network. The 2009 Annual Symposium comprises 4 invited oral presentations, 16 contributed oral presentations and 42 posters, which will be presented during two plenary and two parallel oral sessions, as well as two poster sessions. Following the lines of previous years, the Symposium has been organised as a one and a half-day event. This concept allows sufficient time for accommodating and discussing all contributions. On Thursday evening, a walking dinner has been scheduled in order to provide an enjoyable atmosphere for fruitful scientific exchanges between participants. The organisers and the scientific committee are very grateful that eminent invited speakers, from both industrial and academic backgrounds, have accepted our invitation: Dr. G. Assanto (Univ. di Roma Tre, Italy), Dr. T. Pfeiffer (Alcatel-Lucent Bell Laboratories, Germany), Dr. G. Giuliani, Univ. di Pavia, Italy), and Dr. S. Höffling (Univ. of Würzburg, Germany). We wish to thank all the invited speakers for their willingness to accept our invitation. We also would like to thank all participants and speakers for their contributions to this Symposium. Furthermore, we acknowledge the efforts of the members of the Scientific Committee and the Organising Committee, as well as all the people involved in the organisation of this event. Last but definitely not least, we would like to acknowledge the support from the symposium sponsors: Laser 2000, Newport Spectra-Physics, Alcatel-Lucent Bell Laboratories, BELNET, the Royal Flemish Academy of Belgium for Science and the Arts, and the Vrije Universiteit Brussel. Without their generous contribution, the organisation of this Symposium would not have been possible. On behalf of the Organising Committee, Jan Danckaert, Symposium Chair