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We investigate, by simulations and experiments, the light scattering of small particles trapped in photonic crystal membranes supporting guided resonance modes. Our results show that, due to amplified Rayleigh small particle scattering, such membranes can be utilized to make a sensor that can detect single nano-particles. We have designed a biomolecule sensor that uses cross-polarized excitation and detection for increased sensitivity. Estimated using Rayleigh scattering theory and simulation results, the current fabricated sensor has a detection limit of 26 nm, corresponding to the size of a single virus. The sensor can potentially be made both cheap and compact, to facilitate use at point-of-care.

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Line-defect photonic crystal waveguides exhibit severe propagation losses if they are implemented in semiconductor heterostructures with a weak refractive index contrast. We present, for what we believe is the first time, experimental structures for which we have evidence that fabrication imperfections are not the limiting factor in terms of propagation losses. We demonstrate a loss figure of 335±5 dB/cm, which is an improvement by a factor of about 2 with respect to state-of-the-art values. Simulations show that even lower losses can be obtained with different waveguide geometries. In other words, the dominant loss mechanism is related to the waveguide design, and losses are not expected to decrease upon further optimization of the fabrication process.

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We propose an active waveguide design that provides both low propagation losses (< 20 dB/cm) and the capability for electrical pumping of the photonic crystal waveguide with a vertical contacting scheme. A careful estimation of a large number of parameters is required in order to obtain both properties. The proposed device supports single mode operation at the telecom wavelength λ = 1550 nm and is suitable for the implementation of in-plane active photonic crystal devices, such as semiconductor optical amplifiers and lasers.

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A sensor designed to detect bio-molecules is presented. The sensor exploits a planar 2D photonic crystal (PC) membrane with sub-micron thickness and through holes, to induce high optical fields that allow detection of nano-particles smaller than the diffraction limit of an optical microscope. We report on our design and fabrication of a PC membrane with a nano-particle trapped inside. We have also designed and built an imaging system where an optical microscope and a CCD camera are used to take images of the PC membrane. Results show how the trapped nano-particle appears as a bright spot in the image. In a first experimental realization of the imaging system, single particles with a radius of 75 nm can be detected.

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We investigate manufacturable substrate-type photonic crystal waveguides relying on honeycomb lattice geometry, which shows large photonic bandgaps for TM-polarized light. To the best of our knowledge, air-hole-based photonic crystal slab waveguides with photonic bandgaps for TM-polarized light are experimentally demonstrated for the first time. The results are analyzed with numerical simulations based on the plane-wave expansion and the finite-difference time-domain method. The transmission spectra are measured, and a minimal propagation loss of 1600 dB/cm of TM modes at lambda=1520 nm for lattice constant a=590 nm is acquired with the cut-back method.

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A simple and inexpensive assay for detection of H2S producing bacteria in drinking water was evaluated in Paraguay. Using an improved preparation procedure, results were basically temperature independent in the range of 22-37ºc and correlated well with the presence of total coliform bacteria (96 percent, 28ºc). The assay was not suitable for control of surface water and dug well water due to the frequent presence of non-faecal coliforms. However, it was very suitable for routine control of high quality water-systems, like treated community water systems or deeep-tube well water, where complete absence of coliforms is required a laboratory technician or special equipament. Its use permits a cost-effective routine control of high quality community water systems in developing countries. In addition, this test turned out to be an effective educational tool for heightening the awareness of people towards dangers of unclean drinking water

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A quality conrol assesssment laboratories of clinical analysis was performed in March 1989. Glucose, urea, bilirubin, and GOT were determined in a sample of the same control serum. Statistical evaluation of the results showed that the coefficient of variation (CV) of each parameter was much higher than the internationally accepted values. A further evaluation included an internal precision control and an interlaboratory control. Urea, glucose and cholesterol were determined in twenty samples of the same serum lot per month by each laboratory. About 61 percent had an acceptable CV for glucose, 74.4 percent for urea and 65,6 percent for cholesterol

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