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.
In order to create thermally tunable filter, we fabricate integrated micro-ring resonators with specific
polymers. Their high index contrast (Δn ~ 0.15 at the wavelength of 1550 nm) allows to make small size
waveguides (typically with cross sections of 1.2 × 1.5 μm2). We study the impact of different ring radii and
gaps on the response of filters. Compared to the state of the art with polymers, we have obtained ring
resonators with good characteristics. These results and the high thermo-optic coefficient of polymers
enable us to plan the creation of thermally tunable resonators. For that purpose, we develop a thermal
model of the polymer waveguide behaviour in order to minimize the electrical consumption of a tunable
filter. First experiments of thermal tunability of the micro-ring filter are also reported to work on a range of
40 °C giving a 5 nm shift of the dropped wavelength.
In this article, we discuss the waveguide dimensions optimization aiming to reduce the Vπ. For that purpose, various
cover materials are investigated leading to a minimum effective core area " Aeff". The index contrast (core-cladding) at
λ= 1550 nm, is varying from 0.07 to 0.21. As a result, the Aeff decreases from 12 μm2 down to 2.3 μm2, the total
thickness of the waveguide is thus reduced and consequently the Vπ. Optimal parameters were calculated at λ= 1550 nm
for single mode inverted-rib waveguides structure. The PAS1 a new polymer is used as electro-optic material for the
core. An analytical model taking account the losses by tunnelling, allowed us to estimate the optimum distance between
electrodes to reduce the Vπ which could be about 1.6V ( 0.8 V in a push-pull configuration). Related with the bandwidth
of the modulator, permittivity measurements were carried out on core and cladding polymers as well. The process of
waveguides fabrication is described in details and several waveguides are performed. Finally, a new experimental
technique for precision measurements of the propagation losses in waveguides is presented. The principle is simple, and
the propagation losses measured is found to be independent of coupling conditions.
Conjugated polymer materials have great potential to be suitable candidates for use in all-optical network
communications. They possess ultra-fast response times and a large third order non-linearity compared to minerals (third
order susceptibility χ(3) of conjugated polymers can be 4 orders of magnitude larger than that of fused silica). Such large
non-linearities would allow the fabrication of compact all-optical devices at low power levels. Here we present the first
investigations into the creation of a conjugated polymer single mode optical waveguide based on Poly(3-
AlkylThiophene) (P3AT). We first synthesized the P3AT and tried to control the chemical reaction conditions in order to
improve polymer solubility in common organic solvents. In parallel, we studied the engineering of P3AT single mode
waveguide structures made by photolithography techniques which requires the adjustment of P3AT thermo-mechanical
properties. Recently, we have been able to fabricate and measure the parameters of Strip-Loaded and buried waveguides
with usual polymers. We intend to adapt these processes to obtain the first P3AT single mode optical waveguide.
Polymers are increasingly attractive for the creation of optical integrated circuits particularly owing to a high thermo-optical
coefficient (-10-4 °C-1) which allows to design optical functions tunable according to temperature. For example,
tunable filters or multiplexers are attractive in telecom applications for bringing broadband services to subscribers.
Moreover, the large available range of refractive index, leads to large scale of integration, lowering the fabrication costs
and could be an alternative solution to semiconductor or inorganic dielectric technologies. In this work, optical functions
were created using standard photolithography and Reactive Ion Etching (RIE). Photolithography was used with particular
conditions to improve pattern resolution. Firstly, the details of making optical polymer waveguides and wavelength
micro-ring based filters are given. Optical loss measurements of waveguides and optical characterisation of micro-ring
resonators are also shown for which the results are in agreement with the modelling. Secondly, the same micro-ring
resonators were observed with the temperature change and we noticed that the variation of resonance wavelength is
about 0.2 nm.°C-1. This is just what is needed for the creation of tunable filters or multiplexers without electrical high
power, considering the very small size of the component.
Due to remarkable properties of the chalcogenide glasses, especially sulphide glasses, amorphous chalcogenide films
should play a motivating role in the development of integrated planar optical circuits and their components. This paper
describes the fabrication and properties of optical waveguides of pure and rare earth doped sulphide glass films prepared
by two complementary techniques: RF magnetron sputtering and pulsed laser deposition (PLD). The deposition
parameters were adjusted to obtain, from sulphide glass targets with a careful control of their purity, layers with
appropriate compositional, morphological, structural characteristics and optical properties. These films have been
characterized by micro-Raman spectroscopy, atomic force microscopy (AFM), X-ray diffraction technique (XRD) and
scanning electron microscopy (SEM) coupled with energy dispersive X-ray measurements (EDX). Their optical
properties were measured thanks to m-lines prism coupling and near field methods. Rib waveguides were produced by
dry etching under CF4, CHF3 and SF6 atmosphere. The photo-luminescence of rare earth doped GeGaSbS films were
clearly observed in the n-IR spectral domain and the study of their decay lifetime will be presented. First tests were
carried out to functionalise the films with the aim of using them as sensor.
Polymers are attractive to realize integrated circuits specially because they are very simple to process and are promising for low cost devices. Moreover, beside low cost technology, the large possible range of refractive index, could lead to large scale of integration, lowering the fabrication costs. In some cases, it could be an alternative solution to semiconductor or inorganic dielectric technologies. With usual UV photolithography technology, this work shows that it is possible to perform small guides in order to provide relatively high circuit densification. The refractive index contrast, between optical core and cladding, can be as high as 0.07 instead of 0.02 for the higher contrast in silica Ge doped waveguides. Recently, this contrast has been increased to 0.11 at the wavelength of 1550nm. These materials make possible the patterning of guides having radius of curvature smaller than 200μm. Such curvatures open the way to functions based on microrings that potentially lead to compact wavelength multiplexers. With the view to control the fabrication of polymer waveguides, some features of the process are reported here. For example, shortcomings such as unsuitable film worm aspects are described and solutions are given with requirements assigned to rough materials. Mechanical and thermal properties of polymers have to be adjusted to withstand integrated circuit processing. This paper also presents results concerning the realization of integrated passive microring resonators with this technology.
Generalization of optical communication promotes fabrication of low cost integrated waveguide components. Polymer waveguides are attractive because they are very simple to process and are promising for low cost devices. Up to date, several methods are used to make single mode guides in polymer films. Traditionally, they require multi-step processes involving photolithography, etching and annealing. The UV induced modification of the dielectrics property of polymers is a useful technique for low cost realization of integrated optical circuits and can enable a direct writing process.
This paper reports a demonstration of photo-printed waveguides in an intrinsically photosensitive polymer film. In this polymer (PVCi: PolyVinylCinnamate), local UV irradiation yields a lowering of refractive index even at telecom wavelengths (1300 and 1550 nm). We show significant achievement concerning the index contrasts up to 3x10-2 at 1550 nm. The more the refractive index contrast between the core and cladding increases, the more the guide size and curvature can be reduced, allowing the manufacture of smaller photonic devices. However miniaturization of optical planar waveguides in integrated devices increases the coupling losses from and to single-mode optical fibers. Simulations and experimental demonstrations with PVCi photosensitive waveguides also show the potential of photo-printing process to make efficient index mode converters between small planar waveguides and single-mode fibers. The process uses the post-irradiation of the guide by an UV source to gradually decrease the refractive index from the guide to the fibre.
We report on passive micro-resonator numerical simulations. These structures present a potential functionality in wavelength division access network. We study the influence of the gap between the micro-resonator and the coupling device. We show that greater than 75% optical power transfer to the drop port is enabled in polymer micro-ring by use of a dual-taper coupling method.
V. Boucher, J. Cardin, Dominique Leduc, R. Seveno, R. Le Ny, H. Gundel, C. Boisrobert, S. Legoupy, F. Legros, V. Montembault, F. Odobel, C. Monnereau, E. Blart, D. Bosc, A. Goullet, J. Mevellec
A difunctional NLO Azo-Dye chromophore has been synthesized and polymerization has been performed with a comonomer bearing a side-chain epoxy group. Deposition of the polymer on glass substrates was performed by spin-coating, resulting in uniform films up to 2 μm thickness. The orientation of the chromophore was performed under a "pin-to-plane" positive corona discharge followed by a heat- treatment in order to obtain reticulation of the films. Molecular orientation has been investigated using UV-Vis. and Raman spectroscopy. Poling of the films results in a decay of absorbance as well as in a blue shift of the spectrum. At the same time, the 1600 cm-1 band disappears from the Raman spectra, indicating orientation of the chromophores. Cross-linking has been studied by FTIR and all-optical poling and showed an improved stability of the electro-optic thin films.
We present different glass ion-exchanged waveguide polarizer configurations using an electro-optic polymer (conjugated PMMA-DR1) overlay. The polarizer function is accomplished by modifying the propagation constant of a guided mode by changing the birefringence induced in the polymer by a poling process. A TE pass polarizer with an extinction ratio of 39 dB, has been realized using a corona poling. Further developments require a better control of the poling process. A TE polarizer structure using poling in the vertical direction have also been tested. A TM polarizer with planar metallic electrodes for poling is presented. Design considerations and fabrication results are presented.
We report on a new type of glass ion-exchanged waveguide TE polarizer using an electro-optic polymer (conjugated PMMA-DR1) overlay. The polarization function is assured by poling the polymer in the vertical direction using a Corona process. An extinction ratio of 39 dB is obtained at the wavelength of (lambda) equals 1.3 micrometer. The insertion losses of the device are in order of 7 dB. The performance of the polarizer are investigated. Our experimental investigations show a polarization efficiency over than 40 dB.
A novel hybrid structure for optical modulation and switching is presented. It consists of a thin film of electro-optic polymer spin-coated on passive waveguide made by ion exchange on glass substrate. Two structures corresponding to weak guiding and strong guiding conditions are considered. Design issues and modulation performances are studied for the two structures. Low half-wave voltages less than 10 volts are expected for an interaction length of 1 cm provided the electro-optic coefficient of the nonlinear polymer is 10 pm/V.
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