Two optical techniques, m-lines and spectroscopic ellipsometry, are compared for their suitability for obtaining the wavelength and the temperature dispersion of the refractive index of thin-film layers used in gas detector devices. Two types of materials that are often integrated into gas sensors are studied: a polymer organic–inorganic blend deposited by spin coating typically used in near-infrared waveguides and the ceramic semiconductor SrTi 1−x Fe x O 3 (strontium titanate) doped with iron at concentrations x=0.075 and 0.1 deposited by electron beam deposition. The refractive index dispersion obtained by m-lines and ellipsometry is compared, and the differences between the measured parameters for the two materials are discussed. The chromatic dispersion will be represented by a three-term Cauchy law. An intuitive method for verifying the measured indices using an integrating sphere and reflexion coefficient modeling techniques are also demonstrated. Thermo-optic coefficients in the order of −1×10 −4 /K for both materials are reported, and very low chromatic dispersions are also measured, thanks to the high sensitivity of the m-lines technique. The uniaxial anisotropic properties of the polymer-blend films are measured and discussed in the case of the semiconductor films.
Two optical techniques, “m-lines” and spectroscopic ellipsometry, are compared for their suitability for obtaining the wavelength and temperature dispersion of the refractive index of thin film layers used in gas detector devices. Two types of materials often integrated into gas sensors are studied: a polymer organic-inorganic blend deposited by spin-coating typically used in near infra-red waveguides and the ceramic semiconductor SrTi1-xFexO3 (strontium titanate) doped with iron at concentrations x = 0.075 and 0.1 deposited by electron beam deposition. In this paper, we will compare the refractive index dispersion obtained by m-lines and ellipsometry, and comment on the differences between the measured parameters for the two materials. The chromatic dispersion will be represented by a three term Cauchy law. An intuitive method of verifying the measured indices using an integrating sphere and reflexion coefficient modelling techniques will also be demonstrated. Thermo-optic coefficients of the order of -1×10-4/K for both materials are reported, and very low chromatic dispersions are also measured thanks to the high sensitivity of the m-lines technique.
Unique industrial transfer of write on the fly technique, to produce long and large sub-micron period
gratings on an industrial and commercial laser beam generator (Dilase 750 from KLOE company) has been
successfully achieved. The write on the fly technique, enabling to produce stitchingless long gratings, is based on
a continuous interferogram, generated by a high efficiency phase mask, illuminated with a laser beam and
projected onto a photosensitive film. As the substrate is continuously moving, the technique is able to write large
size gratings, limited by the displacement range of the machine. Demonstration is made on photopatternable solgel
thin films (TiO2 xerogel film) on which 600 nm period gratings, several cm long and a few mm wide were
written. This demonstration opens the way to cost-effective and rapid demonstrators and extends the possibilities
towards high volume products.
The m-lines guided mode technique is demonstrated as a powerful tool for the measurement of wavelength and
temperature refractive index dispersion in thin films. The proper treatment of results reveals measurement uncertainties
of the order of 10-3 for the refractive index, and a sensitivity to changes in this quantity of the order 10-6. Furthermore,
the thickness of the films can be established to a precision of 1nm. Using an optical stack consisting of a silicon wafer
substrate, a low index buffer layer (index 1.52), topped with a polymer blend guiding film, The wavelength dispersion of
the change of refractive index of the guiding film with temperature has been successfully measured. The temperature
dispersion of the refractive index of the guiding layer is of ~ -6.7×10-5 /K.
Microlens, micromirrors, quantum dots and microfluidics networks are some elements illustrating the need of miniaturisation for optics. This paper presents examples of high aspect ratio microstructures obtained with Dilase technology, a direct laser lithography technique in photosensitive layers. Vectorial writing associated with specific laser beam treatment allows imagine fast prototyping and production of a large range of MOE. Integrated optical circuits, such
as optical MUX/DEMUX and splitters are strongly used in telecommunication and sensors industries. Microlens arrays,
micromirrors present a large potential for imagery sector. "Lab on a chip" integrating microfluidic and optical waveguides systems are useful for medical diagnosis.
The optical fiber, which offers a large bandwidth (about five TeraHertz per telecommunication window), can be fully used only if the techniques of multiple access are sufficiently effective. Our technology based on an organic-inorganic material offers a solution for the realization of the coupling and the decoupling of transmitted channels: in addition to the multiplexer with division by wavelength (WDM) based on multimode interference couplers, we present here a system of multiple access with division by code (CDMA) using multimode interference couplers as well.
The existence of optical amplification at 1.55 micrometers wavelength in channel waveguides using Erbium dopent and 980 nm laser pump involves an OH and CH3 groups quantity as low as possible. Moreover, a high refractive index variation between the guide and the cladding is necessary to induce a maximum confinement and then increase the dopent efficiency. In this way, we propose a study of different routes we explored to reach this goal: use of F catalysis (to enhance condensation), hybrophobic precursors to reduce the OH quantity, and a diacrylate monomer whose reactivity allows a high refractive index change under UV light exposure.
To confirm the credibility of the integrated optical circuits based on organic-inorganic materials, the problem of connection with an optical fiber, but also between inter and intra-cards or with a matrix of laser diodes such as VCSEL have to be resolved. In this work, we propose to integrate in an optical device some `objects' which could simplify the alignment procedure in the both last cases. We fabricated a 45 degree(s) tilted mirror made by EBID method. This mirror was placed right in front of an optical waveguide output.
An organic-inorganic materials associated with a direct printing by UV exposure was used to make MMI couplers. A 1 X 32 splitter and a 4 X 4 splitter/combiner were designed and achieved for working at 1.55 micrometers wavelength. The 4 X 4 splitter/combiner was then used to design a 2 nm selective MMI-Phasar working around 1.55 micrometers .
The development of original devices requires the calculation of the propagation in guiding structures with complex geometry, in particular, when optical circuits are stacked on several levels. New software tools adapted to our devices, in particular, multi level circuits were developed, on the basis of directed programming objects (Java), user- friendly, evolutionary, and executable on the Internet network.
Sol-gel process appears as an interesting alternative to realize optical integrated devices working at 1.55 micrometers wavelength in reason of the low cost of the materials and equipment used and the good performances realized. The principle of fabrication is to deposit a photocurable sol- gel layers on a substrate like silicon and to imprint waveguides through a predefined mask with an UV light. The buried quasi-symmetrical waveguides achieved are well adapted to the use of the Galerkin's method associated with Hermite-Gauss basis functions to resolve scalar, semi- vectorial and vectorial waves equations. Optical integrated devices can be simulated in many steps. In a first time, the device is dividing into several cross sections. Transverse field is, then, calculated by series expansion to determine the mode amplitudes of each section. The field propagation is determined in establishing a relation between the coefficients of two consecutive sections. The description of the transverse sections is easily realized region after region. Each region presenting a constant refractive index, an analytical formulation is given. From this calculation method, the optimizations of a transverse structure achieved by sol-gel process is made according with the fabrication parameters. Propagation method is, then, applied an can be generalized to study optical integrated passive devices.
Organic-inorganic hybrid material realized by sol-gel process is a new promising technology for the fabrication of integrated optical circuits. Effective devices are already achieved. Two approaches are studied here to improve the density of integration: crossed and stacked waveguides. Both processes are compatible with our organic-inorganic material. One level devices with crossing waveguides as well as multilevel devices have been studied and made: neither additional insertion loss nor crosstalk have been measured. Theoretical studies show the possibility to fabricate vertical coupler in a multilevel structure by adjusting the buffer layer thickness between guiding layers.
Optical amplification performance is channel waveguides involves the absence of OH groups to have Erbium doping efficiency and a high refractive index variation between the guide and the surround material to have the maximum confining as possible. In this way, we propose a new hybrid material using a hydrophobic silica precursor to reduce the OH content mixed to a diacrylate monomer which reactivity allow a high refractive variation under UV light exposure.
The lightwave communication technology is experiencing tremendous growth in the volume and flow of information. Spectral discrimination filtering, wavelength division multiplexing and dense wavelength division multiplexing are making it possible. The high refractive index modulation and design flexibility of Polyglass material makes it very attractive to produce such devices.
Among the fabrication techniques of integrated optical devices, the sol-gel chemistry is now performant enough to make thin films of transparent materials with controlled purity and composition, at low temperature. Semi-mineral semi-organic solutions allow dip coating followed by low temperature baking to deposit vitreous films up to eight micrometers thick which are free from cracks. A local polymerization process through UV exposure enables hybrid components compatible with electronic planar silicon or III- V components. This UV imprinting method is used here to make index modulation gratings with use of a holographic equipment as an alternative to the use of a costly phase mask. Gratings have been imprinted on various sol-gel films; single layer, with a protective coating, and/or with an isolating buffer layer from the substrate, which is silicon and glass. Diffraction magnitude is measured in the various cases, as well as analysis and computer simulations are performed. Wavelength filters are experimented and studied. This shows the potential of this low cost technology in integrated optics, for application in telecommunications.
We present design considerations and fabrication results for a vertically integrated waveguide polarization splitter. Fabrication techniques of shadow reactive ion etching and variable photolithography exposure produced the required vertical waveguide structures. The fabricated vertical waveguide bends exhibit excess loss of only 0.2dB. By constructing this vertical bend with a birefringent polyimide, simulation results show the possibility of a polarization splitter wit an extinction ratio of over 15dB. We demonstrate preliminary waveguide experiments showing the practicality of these structures as 3D integrated optical devices.
The sol-gel process is an interesting alternative to make glass integrated optics components. Basically, reasonable performances can be reached with low cost fabrication. The sol-gel process is coupled to an one-step method to imprint channel waveguides as basic parts of optical integrated circuits. The basic one layer structure is enriched with a protective layer and a buffer layer and we show here the advantages of these additions in the quality of the propagation. The fabrication of gratings is also described since they can be also easily imprinted with two methods. Passive devices illustrate the possibility of this technology.
New processes are developed to produce surface, ridge and buried sol-gel glass waveguides by photo-inscription using a ultraviolet light source. The fabricated waveguides demonstrate very low propagation losses (approximately 0.1 dB/cm). Several integrated optical devices such as cascaded Y-branch power splitters, directional couplers, Mach-Zehnder interferometer wavelength division multiplexers have also been produced.
We describe fabrication and characterization of UV-light imprinted sol-gel silica glass waveguide 1 X 8 beam splitter on silicon. Waveguide fabrication parameters carried out for channel waveguide realization were adapted at this new design. The splitter exhibited a relatively uniform output and a configuration loss of 0.83 dB at 1.55 micrometers wavelength.
We describe a new simplified process for inexpensive fabrication of low-loss (0.1 dB/cm) glass waveguides on silicon by ultraviolet light imprinting in photosensitive, organically modified sol-gel silica glass films prepared by one-step dip-coating process. The fabrication process is appealing because the buffer layer between waveguide and substrate is eliminated, and waveguides can be made in a few steps using low-cost equipment.
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