A novel integrated sensor for the simultaneous measurement of layer refractive index and thickness based on evanescent fields is proposed. The theoretical limits for the accuracy of the sensor were examined for the example of a TiO2 layer. The influence of production tolerance on the accuracy was evaluated. In the experimental part of this work, a sensor chip containing nanowire and nanorib waveguides realized in silicon on insulator technology was used to demonstrate the detection of refractive index and thickness of a TiO2 atomic layer deposition (ALD) layer.
We present a new concept for the optical interfacing between vertical III-As nanowires and planar Si waveguides. The nanowires are arranged in a two-dimensional array which forms a grating structure on top of the waveguide. This grating enables light coupling in both directions between the components made from the two different material classes. Numerical simulations show that this concept permits a light extraction efficiency from the waveguide larger than 45% and a light insertion efficiency larger than 35%. This new approach would allow the monolithic integration of nanowire-based active optoelectronics devices, like photodetectors and light sources, on the Si photonics platform.
The realization of an integrated delay line using tapered Bragg gratings in a drop-filter configuration is presented. The device is fabricated on silicon-on-insulator (SOI) rib waveguides using a Deep-UV 248 nm lithography. The continuous delay tunability is achieved using the thermo-optical effect, showing experimentally that a tuning range of 450 ps can be obtained with a tuning coefficient of -51 ps/°C. Furthermore the system performance is considered, showing that an operation at a bit rate of 25 Gbit/s can be achieved, and could be extended to 80 Gbit/s with the addition of a proper dispersion compensation.
Optics and Photonics , Crystallization , Equipment Design , Filtration , Photons , Signal Processing, Computer-Assisted , Silicon/chemistry , Temperature , Tomography, Optical Coherence/methods , Ultraviolet Rays
We present the design, fabrication and characterization of Bragg reflectors on silicon-on-insulator rib waveguides. The fabrication is based on a new double lithographic process, combining electron-beam lithography for the grating and photolithography for the waveguides. This process allows the realization of low loss reflectors, which were fully characterized. The influence of the etching depth and of the waveguide geometry on the reflector performance is considered. We demonstrate a reflectivity larger than 80% over a bandwidth of 0.8 nm with an insertion loss of only 0.5 dB. A thermal tunability of the device is also considered, showing that a shift of the reflected wavelength of 77 pm/K is possible.
INTRODUCTION: Malignant tumors of the musculoskeletal system are rare, and their symptoms are non-specific. The diagnosis of primary malignant tumors of bone or soft tissue by tissue biopsy is necessary before multimodal treatment with chemo- and/or radiotherapy and resection can be provided. These biopsies are straightforward surgical procedures; they must, however, be performed according to the guidelines if high rates of error and complications are to be avoided. METHODS: Selective literature review. RESULTS: Biopsies are either incisional or excisional. There are guidelines for the performance of both kinds. The biopsy channel is inevitably contaminated with tumor cells and thus must be completely removed together with the tumor. Excisional biopsies are indicated only for the histopathological diagnosis of small (< 5 cm), epifascial soft-tissue tumors and small, slowly growing bony tumors that are considered most likely to be benign. If in doubt, an incision biopsy should be performed. DISCUSSION: The complication rate of tumor biopsies is known to be higher when they are performed in an institution without extensive experience in the treatment of sarcoma. Thus, patients with musculoskeletal tumors that are suspected of being malignant should be referred to a suitable tumor center for biopsy.
