Research on sensors has experienced a noticeable development over the last decades especially in label free optical biosensors. However, compact sensors without markers for rapid, reliable and inexpensive detection of various substances induce a significant research of new technological solutions. The context of this work is the development of a sensor based on easily integrated and inexpensive micro-resonator (MR) component in integrated optics, highly sensitive and selective mainly in the areas of health and food. In this work, we take advantage of our previous studies on filters based on micro-resonators (MR) to experiment a new couple of polymers in the objective to use MR as a sensing function. MRs have been fabricated by processing SU8 polymer as core and PMATRIFE polymer as cladding layer of the waveguide. The refractive index contrast reaches 0.16 @ 1550 nm. Sub-micronic ring waveguides gaps from 0.5 to 1 μm have been successfully achieved with UV (i-line) photolithography. This work confirms our forecasts, published earlier, about the resolution that can be achieved. First results show a good extinction coefficient of ~17 dB, a quality factor around 104 and a finesse of 12. These results are in concordance with the theoretical study and they allow us to validate our technology with this couple of polymers. Work is going on with others lower cladding materials that will be used to further increase refractive index contrast for sensing applications.
The Laser Doppler flowmetry (LDF) is a non-invasive method for estimating the tissular blood flow and speed at a microscopic scale (microcirculation). It is used for medical research as well as for the diagnosis of diseases related to circulatory system tissues and organs including the issues of microvascular flow (perfusion). It is based on the Doppler effect, created by the interaction between the laser light and tissues. LDF measures the mean blood flow in a volume formed by the single laser beam, that penetrate into the skin. The size of this measurement volume is crucial and depends on skin absorption, and is not directly reachable. Therefore, current developments of the LDF are focused on the use of always more complex and sophisticated signal processing methods. On the other hand, laser Double Doppler Flowmeter (FL2D) proposes to use two laser beams to generate the measurement volume. This volume would be perfectly stable and localized at the intersection of the two laser beams. With FL2D we will be able to determine the absolute blood flow of a specific artery. One aimed application would be to help clinical physicians in health care units.
Ion-exchange in glass substrate has long been an enabling technology for optical waveguides device manufacturing.
Thus, in the last years, hybridization of ion-exchanged glass waveguides components has become a promising method
for functional integration. In that context, we propose a Integrated acousto-optic Polarization Analyzer Sensor (IPAS)
made by ion-exchange in a glass substrate. The IPAS consists in two Y-junctions that give three different outputs. The
first one is simply one output waveguides of the first Y-junction. The two other outputs are the waveguides following the
second Y-junction. A piezoelectric plate is placed over the entrance waveguide of the second Y-junction. It creates an
artificial anisotropy when it is excited electrically. For each one of the three output signals, a polarizer is inserted
between the waveguide's end and a photodetector. The IPAS is a compact hybrid realization insensitive to vibrations and
easy to realize. It is capable to determine, with adequate signal processing, the polarization state of a light beam.
Experimental results are obtained with a single buried straight waveguide made by low birefringence Ag+↔Na+ ion-exchange.
The measured polarization state is compared with a commercial polarization analyzer.
Optical interferometer displacement sensors are well known for their high resolution, up to 10-7 m in a stabilised environment, over a wide measuring range which can reach several meters. Moreover, the measures are carried out without any mechanical contact with the target object. Two optical outputs are however needed to determine the displacement direction. A glass integrated sensor with only one optical output that still measures the displacement direction is proposed here. It is derived from a Michelson interferometer but is realised by ion-exchange on a glass substrate. A piezoelectric element placed over the reference arm produces a longitudinal acoustic wave that creates a small phase modulation on the reference light beam at a high frequency (1.28 MHz). A small modulation of the output signal is thus produced. The direction determination is based on the comparison between the phases of the excitation acoustic signal and of the high frequency part of the sensor's output signal after proper signal processing. A theoretical and an experimental demonstration of that principle are presented. A precision of 158 nm was obtained with a simple numerical signal processing.