Infrared sensors with application in infrastructures security
The main objective of this project is to develop non-dispersive optical sensors, having high sensitivity, to operate within the infrared spectral range. These sensors can be used for hazardous gas detection in industrial buildings to increase the security level of this type of infrastructures.
The main advantage of the proposed sensors is their high selectivity with respect to the types of gases detected (calibration on absorption spectral range specific to gas of interest – e.g. methane, carbon monoxide / carbon dioxide), which will reduce the risk of false negative or false positives signals.
The innovative side of the proposed project is based on achieving a high selectivity for the sensor by overlaying very precisely the spectral characteristic of the infrared source and the detector response that has the gas absorption bands in the Mid-IR range (3 μm – 8 μm). The novelty of this project consists in the application of a new concept in photonics, namely the metasurface, for controlling and adjusting the spectral characteristic (reflection, transmission, absorption, emission) of a micro / nanostructured surface.
National Institute for Research and Development in Microtechnologies (coordinator) (IMT)www.imt.ro
National Institute for Laser, Plasma and Radiation Physics (INFLPR),www.inflpr.ro
IMT is responsible for design of plasmonic metasurfaces, developing gas sensors and of related manufacturing technologies. INFLPR carries out the optical and mechanical tests and characterizations, including calibration of the sensor.
During the Phase I the following activities were carried out:
The project preliminary results obtained at this stage were presented at international conferences/workshops by our team younger researchers, Roxana Tomescu (project responsible, IMT), Laura Mihai (project responsible, INFLPR) and Bodgan Călin (INFLPR).
In addition, three new research assistant positions were occupied within the project: 2 positions – IMT-Bucharest and 1 job position – CETAL-INFLPR. The new researchers have the opportunity to use new generation equipment for simulation, design, manufacturing and characterization of developed system within the project, at the new research infrastructures CENASIC/IMT and CETAL-PhIL/INFLPR.
An example of metasurface with gold cylindrical resonators on Al2O3 substrate:
a) the sketch of the structure
b) the structure layout used in simulations
Detection of proposed system: at the level of the thermal emission source, an electric current is applied which determines the heating of the resistance by Joule effect. The specifically tailored metasurface, placed directly over the classical thermal source, will absorb all the radiation spectrum emitted and will filter and transmit to the detector wavelengths specific to the absorption lengths of the different gases that are found in industrial infrastructures; Fresnel lenses are used to collimate the radiation, and a commercial detector will be used for the radiation detection emitted by the selective source.
Three components of the proposed system were technologically fabricated and characterized during 2019: the large-spectrum radiation source, the metasurface specifically configured and the Fresnel lenses. In order to optimize the geometries and technological processes used, the following objectives were achieved:
Figure 1 Scheme of the gas detection system
Figure 2 Components of the thermal radiation source: a) Platinum resistance consists of 2 meanders (layout) and images of the obtained technologically resistor consists of 3 meanders; b) Proposed metasurfaces used as perfect absorber (layout and SEM image)