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Programmable multi-wavelength Mid-IR source for gas sensing

Periodic Reporting for period 3 - MIREGAS (Programmable multi-wavelength Mid-IR source for gas sensing)

Reporting period: 2017-01-01 to 2018-10-31

Cost effective multi-wavelength light sources are key enablers for wide-scale penetration of gas sensors at Mid-IR wavelength range. We targeted in demonstrating an innovative light source that would cover 2.7…3.5 µm wavelength range with a resolution <1nm with switchable and tunable spectral bands. The source would allow for the fabrication of an affordable multi-band gas sensor with good selectivity and sensitivity for safety and security as well as industrial process monitoring applications. The unit price should be lowered in high-volumes by utilizing tailored molded IR lens technology and automated packaging and assembling technologies. The project was targeting to fill a gap: affordable sources are not available at Mid-IR wavelengths.
In conclusion, we demonstrated the feasibility of the basic components needed for the implementation of a programmable Mid-IR lights source: The Si PIC filter to provide narrow spectral bands, Mid-IR lenses fabricated by the use of hot-embossing technology and SLED technology to reach ultimately at 3 um wavelengths with reasonable power. In addition, we demonstrated the use of the SLED for gas sensing with an external filter instead of the PIC filter. A multi-gas sensing platform was also developed.
The consortium was composed of VTT, TUT and ITME as research partners and Vaisala, Airoptic, GasSecure and VIGO as industrial partners representing the complete value chain from devices and components to gas sensor manufacturers. The position of these organizations in their respective markets guarantees that the project results will be widely exploited providing the companies with a technological advantage over their worldwide competitors thus creating new high-tech jobs and technology leadership in Europe.
The innovation was to develop a novel, programmable, multi-wavelength, light source for IR gas sensors. The technology is seen an enabler for growing business in the gas sensor applications provided by the industrial beneficiaries. The technology development was divided into three phases: Phase I, Multi-wavelength source in lab validation (TRL 4), Phase II 3500-nm multi-wavelength source in lab validation (TRL 4) and Phase III 3500-nm multi-wavelength source industrial validation (Secondary option 2550nm source industrial validation) (TRL 5). The development phases were modified based on the requirements reported in WP1 in such a way that Phase II represents an intermediate step targeting to wavelengths 2.5 … 2.7 µm requested by the end-users. Phase III represents the final target at 3500nm still including the 2550nm target as a backup.
The workflow was organized into seven workpackages. In the beginning, the specifications for the light source and gas sensor demonstrators were defined by the end-user considering the technological constraints provided by the research partners. Then the basic components, including Mid-IR SLED devices, Si PIC filters and Mid-IR lenses, were designed, processed and tested in respective workpackages. Components were packaged and integrated in order to be used in end-user setups. Finally, the gas sensing system based on the use of the components were tested at end-user laboratories.
We demonstrated a 2.65µm single-mode SLED with 300-nm bandwidth, 3µm multimode SLED with ~550nm bandwidth and 44-nm tuning range with an external cavity tuneable laser using 2.65µm gain element. The sources are applicable for gas sensing. We demonstrated gas sensing with the 2.65 µm SLED using a 0.5 m absorption length. Commercial sensors use typically 4 µm absorption band and ~5 to 15 cm absorption length. The absorption band at 2.65 µm is 100 times weaker than at 4 µm wavelength. Our demonstrator, however, shows that a 10-fold improvement in the signal-to-noise ratio is reachable at 2.65 µm when using sophisticate detection techniques and SLED.
Echelle grating PIC utilizing low-loss Euler bends was demonstrated potentially providing narrow band selective gas sensing. Different waveguide designs were demonstrated proving specificity for different gases.
The spectral bandwidth of a MOEMS filter at 2.65 µm is on the order of 40 nm. With the Echelle grating narrow spectral bandwidth is achievable. However, it was difficult to measure the bandwidth at 2.65 µm wavelength. The measured band-width of ~5-nm was limited by the resolution of the grating spectrometer. At 1550 nm narrow-band Echelle filters were demonstrated with 1-nm bandwidth.
We estimate 35 k€ price for a multi-gas instrument using discrete DFB lasers; 1 k€ is reachable for a sensor based on wide-band SLED. It is not possible to estimate the cost of the integrated SED-PIC light source due to the difficulties met in the packaging. However, when using wafer-level testing and packaging techniques, the target price 300€/unit should be reachable.
Within the frame of the project, we were able to successfully build and test the following gas measurement setups/demonstrators: 1) C1-C5 detection (Primary application), 2) Acetylene/Ethylene/Ethane (Primary application), 3) H2O detection (Secondary application) and 4) CO2 detection (Secondary application). The overall performance of the test analyzers was satisfactory. Fully unattended operation was demonstrated for the CO2 and C1-C5 analyzer.
MIREGAS was targeting to reduce the dependence of end users on critical technologies that are non-European origin and to build automated manufacturing capabilities in order to ensure that the manufacturing of photonic sensor products, such as, gas sensors, will be carried out in Europe.
The basic components, SLED, Si PIC and Mid-IR lenses, which are state-of-the-art, were developed as well as their novel integration concepts and their use for gas sensing were demonstrated. The components have potential to considerably reduce the price of multi-gas gas sensors. Thanks to the project, the research partners are more capable in serving the industry: VTT to provide Mid-IR PICs, ORC SLEDs and ITME Mid-IR lenses. There is also potential for spin-offs or technology licencing by the research partners. AirOptic developed their multi-gas sensing platform for industrial applications and they are going to launch new products; VIGO launched new detector products and revised their long-term strategy for targeting to be a supplier for the full value chain of gas sensors.
MIREGAS was an excellent forum for networking. Nationally, VTT, ORC and Vaisala are continuing these activities in the Business Finland funded RAPSI-program, which began in July-2018. The collaboration between Finnish, Polish and Norwegian partners will continue at least in the form of joint research project funded by the European Commission. Commercial relations are also possible at least between VIGO and end-user companies AirOptic, Vaisala and GasSecure.
The exploitation activities beyond the MIREGAS project are the following: VTT gained more expertise in PIC design and manufacturing as well as photonics packaging, and therefore, are capable in serving the industry better in the future. ORC built the grounds for possible spin-off company commercializing the SLED technology. ITME is preparing for transferring the lens manufacturing knowledge to industry. VIGO launched new products. AirOptic is going to launch new products on this field in 2019. Vaisala and GasSecure are still in research/observer mode for the technology.