Centre for Sensors, Instruments and Systems Development

Universitat Politècnica de Catalunya

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PLEXOF - Development of a new industrial process to obtain photochromic beam splitters for plastic optical fiber multiplexers (POF)

The PLEXOF project, under the funding of the RETOS collaboration program (RTC-2016-5526-8) of the Ministry of Economy and Competitiveness, for the development of a new, easily scalable process for manufacturing photochromic beam splitter filters based on nanotechnology, concluded its second and last stage on 06/30/2019. During the development of the project, the partners (Lurederra, TECNAN, SnellOptics and CD6) focused on the development of filters in a totally different way than usual, creating the filter in situ by spraying a nanotechnologic formulation. This novel alternative involves several steps, including the production of nanoparticles based on active metal oxides of determined composition by means of Flame Spray Pyrolysis (FSP) technology, their incorporation into different liquid matrices that allowed to give rise to the coating through a simple spraying and finally, the drying process to the air, along with the development of the methodology of characterization of the optical properties of the nanoparticles throughout the different stages of the process defining active material dosage among other parameters.

More specifically, nano-coatings have been developed incorporating nanoparticles with optical properties of interaction with light in order to obtain and evaluate two types of filters: Passive Beam Splitters (PBS) and pass-through filters (PTF). With regard to the developed PTF nano-coatings, these present a higher absorbance level as we approach the infrared wavelengths. In this way they can be used successfully in applications in which it is of interest to absorb only wavelengths corresponding to said area of the electromagnetic spectrum. This effect has been incorporated into the final demonstrator.

On the other hand, with respect to the nano-coatings developed as PBS, instead of absorption, the selected mechanism was the IR radiation reflection, so that by modulating the dose of active nanomaterial in the matrix, 25/75, 50/50 or similar coatings were achieved. In this case, the reflective activity to the IR (close to 100%) of several mixed nano-oxides in powder format has been obtained  and validated in the project even at pilot scale.

Also, said nanoparticles have been successfully incorporated into a liquid matrix capable of curing at room temperature, and adhering to both glass and polymers, having been validated on PC and PMMA. Dispersion particle sizes and transparency to visible radiation were adequate. Even, IR reflectance measurements of the liquid matrix were made with the active nanoparticles incorporated, and values around 40% could be seen, a priori suitable for the pre-defined 25/75 variants. In addition, the development of the optical characterization process of the materials used during the different stages of the process has allowed us to analyze the intrinsic properties of the nano-materials used, observing that the interaction with the light is due to the active material, since the matrix without nanoparticles does not interact with incident light.

Finally, another of the most interesting results of the project is related to the manufacturing process of the filters, due to the advances in the adjustments of the formulations of the matrices for the specific application of the project: matrices, capable of properly integrating different active nanomaterials, with good viscosity properties, etc. to be able to atomize in a spray, dry, cure and generate the layer.
CD6 Centre for Sensors, Instruments and Systems Development
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