In this work a portable analytical biosensor for real-time extracellular monitoring of released hydrogen peroxide (H<sub>2</sub>O<sub>2</sub> )
is presented. The biosensor is based on the optical detection of the cytochrome c (cyt c) oxidation state. The setup
consists of an integrated microscope combined with a compact spectrometer. The light being absorbed by cyt c is
enhanced via multiscattering produced by random aggregates of polystyrene beads in a cross-linked cyt c matrix. Using
ink-jet printing technique, the sensing elements, namely cyt c loaded polystyrene aggregates, are fabricated with high
reliability in terms of repeatability of size and sensitivity. Additionally, the sensing elements are enclosed in a
microfluidic channel assuring a fast and efficient analytes delivery. As an example, the effect of trace concentrations of
functionalized cadmium selenide/zinc sulfide (CdSe/ZnS) core shell quantum dots on the green algae <i>Chlamydomonas
reinhardtii</i> is investigated, showing extracellular H<sub>2</sub>O<sub>2</sub> release with different production rates over a period of 1 hour. In
conclusion, the presented portable biosensor enables the highly sensitive and non-invasive real-time monitoring of the
cell metabolism of <i>C. reinhardtii</i>.
A volume hologram recorded with a lens array is proposed as a transflective screen for Head Worn Display (HWD)
systems. Design, fabrication as well as proof of concept are reported. Light from a projection system, with similar
properties to one mounted on the side of an eyewear, is efficiently diffracted towards the eye with an angular spread
given by the numerical aperture of the lenses forming the lens array. Using a dual-focus contact lens, high-resolution
images can be added to the HWD user’s normal vision, as light from the surrounding environment is transmitted through
the screen with low aberrations. This screen offers the possibility for small footprint and large field of view HWD’s.
The design, simulation, fabrication and characterization of two SU-8 based microoptoelectromechanical systems
(MOEMS) are presented in this paper: an optical accelerometer and a variable optical attenuator (VOA). Both devices
consist on a quad-beam polymer structure and can be fabricated with a simple technology, requiring only two
photolithographic steps. In order to overcome the fibre optics positioning, self-alignment structures have been integrated
on the devices. Working principle of both devices is based in the modulation of the optical losses (when an acceleration
or voltage is applied at the accelerometer or the VOA, respectively). In order to achieve the optimal behaviour, several
quad beam configurations have been studied by means of mechanical and optical simulations. An optical sensitivity of
16.58 dB/g has been estimated for the optimal configuration of the accelerometer. The experimental results show a good
agreement, with measured optical sensitivities of 13.1 dB/g and 17.5 dB/g for negative and positive accelerations,
respectively. On the other hand, the VOA has been electrothermally actuated, taking advantage of the high thermal
expansion coefficient (CTE) of the SU-8, to achieve high optical attenuation (20 dB) with low power consumption
A ray tracing simulation method for integrated optics hollow waveguides has been developed. This method has been
tested on Silicon waveguides with good results, providing a suitable design tool for new devices using this type of
The simulations allow the design of new guiding structures based on hollow waveguides, like input tapers to reduce the
insertion losses. The study of the hollow waveguide behavior with different refractive indices opens the way for their use
as refractive index sensors.
Deflection of a microcantilever caused by any kind of biochemical reaction occurring on its surface
can be detected with subangstrom resolution if an appropriate detection technique is exploited. This
kind of transducers has become widely used in biological research since a few years ago. Usually,
for the readout of the nanomechanical response of the micro beams to bio-specific interactions, a
technique similar to one used in the atomic force microscopy is employed. The optical read-out
method has some disadvantages, such as low degree of integration and difficulties in work with
arrays of cantilevers. In the technique presented in this work the cantilever itself is an optical
waveguide butt-coupled with another one. The device is fabricated as an array of 20 waveguide
cantilever channels which allows for higher integration level. The analysis of the capabilities of the
device, the problems associated with the design and the fabrication of the device, the choice of the
material and the technology for the fabrication of very flat cantilevers have been successfully
addressed. The characterisation of the device was done, showing that the resolution of the device is
comparable with the one using the optical lever read-out. Results of the simulations and
experimental data on the optical cantilevers coated with an absorbent material will be presented. The
choice of the appropriate thickness of the absorbent material on the cantilever surface allows for
acceptable losses, for single mode behaviour and adjustment of the initial displacement of the
Butt coupled optical waveguides are well known in integrated optics by high sensitivity of energy transfer to their misalignment with respect to each other. This might be detrimental if efficient and firm coupling from one light guide to another is needed, for example, coupling from a fiber to a waveguide on chip. However, this phenomena is efficiently used for sensing applications, where small misalignment between two objects provided with the waveguides can be detected. In this work we studied the abilities of this method to detection of ultrasmall displacements of microcantilevers frequently used in biological research. In the proposed design the cantilever itself acts as a waveguide operated in visible range. The simulations demonstrated ability to detect cantilever deflections with sensitivity of 18 fm/Hz<sup>1/2</sup>. The capability of detection with subangstrom resolution in the dynamic mode was demonstrated experimentally in air. The preliminary experiments in liquids are presented. The technique can be considered as an alternative to the known methods used for read-out of response of microcantilevers to external nanomechanical forces exerted on them.
Multimode interference devices based on silicon hollow waveguides have been designed, simulated, fabricated and characterized. Adequate confinement of light into a hollow waveguide and minimization of the propagation losses require a roughness of the structure below the working wavelength. This assures to have mirror behavior at the facets that optimize the Fresnel reflections. In order to achieve this low roughness and a perfectly vertical walls, to obtain a rectangular shape, an optimization of the fabrication process, especially deep reactive ion etching process, has been made. The numerical and experimental anti-symmetrical behavior for symmetrical and anti-symmetrical out waveguides in anti-symmetrical multimode interference devices is in accordance with the theory of multimode interference effects. The excellent behavior and properties of these devices shows the silicon hollow waveguides excellent for the design of integrated optical devices.
The characterization and optimization of a quad beam all-polymer optical accelerometer is presented in this paper. The
working principle is based in the intensity modulation, due to the misalignment between three waveguides when
acceleration is applied. Analytical, mechanical and optical simulations predict a high sensitivity of the proposed devices.
Optimization of both the seismic mass/mechanical beams joint and the sacrificial layer are also presented. Experimental
results shows an optical sensitivity of at least 15.8 dB/g, with an asymmetrical behavior attributable to a small
misalignment between the waveguides when no acceleration is applied.