During the Phase I the following activities were carried out:

• the specifications of each component of the gas detection system were obtained together with the corresponding schemes.
• two types of Fresnel lenses were designed to collimate radiation from the source and to focus the beam on the commercial gas detector.
• different types of absorbing metasurface have been also studied to obtain the selective radiation sources and, at the same time, various geometries configured on three types of substrates, obtaining maximum absorption for several gases of interest.
• moreover, at this stage, a technological flow necessary for the manufacturing of the desired structures was proposed;
• the first technological tests were carried out, thus obtaining resistors based on meanders and metasurfaces made of circular resonators. The techniques used for this purpose were photolithography, lift-off method, sputtering or atomic layer deposition.
• based on manufactured test structures, the experimental setups were developed to characterize the components of the gas sensor.

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.

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:

1. Design and simulation of a classical thermal source (resistor): using two different simulation approaches: i) using the Ansys Icepack software and applying a power of 0.2 or 4W; ii) using the COMSOL Multiphysics software and applying a voltage of 10V. Thus, the used materials, geometry (2 or 3 meander configurations with narrow or wide pads) and its area (1cm²) were established;
2. The geometry of the absorbent metasurfaces configured specifically for absorption at certain wavelengths has been established;
3. Fresnel lenses have been designed to operate at specific wavelengths, taking into account the results of metasurface absorption measurements (3.3 µm, 4.25 µm, 5.25 µm).
4. Specific technological flows were established, followed by the fabrication and morphological characterization of the three components necessary for the development of the proposed gas detection system;
5. The absorption of the metasurface as well as the emission of the radiation sources were measured.

In Project 3, taking into account the results obtained in the previous stages, the optical components of the detection system were optimized and the corresponding experimental models were made.

Moreover, an experimental model for the hazardous gas detection system was developed. The optimized optical components were characterized by the experimental procedures developed in the previous stages, for each component being prepared a test report.

For the characterization in optical power and wavelength of the detection system, an experimental procedure was developed and the preliminary experimental procedure was drawn up, the final variant being performed at the next stage. Because it is desired to test the detection system and from the point of view of its resistance to shocks, the experimental assembly of the vibration test was performed and a variant of the measurement procedure was drawn up.

The results obtained at this stage were presented at 2 international conferences. Also, a patent application was filed by the two partner organizations, a scientific paper was published in an ISI conference volume, a paper was published in an ISI journal.