We present quantitative measurements of the interaction between a guided optical wave and a two-dimensional photonic crystal using spontaneous emission of the material as an internal point source. This is the first analysis at near-infrared wavelengths where transmission, reflection, and inplane diffraction are quantified at the same time. Low transmission coincides with high reflection or in-plane diffraction, indicating that the light remains guided upon interaction. Also, good qualitative agreement is found with a two-dimensional simulation based on the transfer matrix method. [S0031-9007(97)04591-2]

Microcantilever-based biosensors are a promising tool to detect biomolecular interactions in a direct way with high accuracy. We show the development of a portable biosensor microsystem able to detect nucleic acid hybridization with high sensitivity. The microsystem comprises an array of 20 micromechanical cantilevers produced in silicon technology, a polymer microfluidic system for delivery of the samples, an array of 20 vertical cavity surface emitting lasers (VCSELs) with collimated beams thanks to an integrated microlens array, an optical coupling element to provide the optical path required, and chips with the photodetectors and the CMOS circuitry for signal acquisition and conditioning, capable of measuring the cantilever deflection with sub-nanometer resolution. Robust immobilization and regeneration procedures have been implemented for the oligonucleotide receptor sequences. In a further innovation, an optical waveguide cantilever transducer has been also developed in order to improve the final performance of the device. This has a number of advantages in terms of a simple optical geometry and improved sensitivity.

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Optical feedback interferometry (OFI) performance for microscale-flow sensing is studied theoretically and experimentally. A new numerical modeling approach for OFI flow meter spectrum reproduction is presented in this work to study the optical effect on the signal due to the micro-scale channel geometry. Two well-defined frequency peaks are found in the OFI spectrum, this phenomenon can be attributed to the reflection of the forward scattered light on the channel rear interface. The flow rate measurement shows good accuracy over a range of fluid velocities from 16.8 mm/s to 168 mm/s, thus providing a promising tool to study and to optimize the OFI microfluidic sensor system.