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European Joint Doctorate Programme on Optical Sensing using Advanced Photo-Induced Effects

Periodic Reporting for period 1 - OPTAPHI (European Joint Doctorate Programme on Optical Sensing using Advanced Photo-Induced Effects)

Reporting period: 2020-01-01 to 2021-12-31

Photonics, the science of generating and manipulating light, is a key technology of the 21st century; it has been identified by the European Investment Bank as being one of the “building blocks of the next digital revolution”. Photonics underpins all aspects of modern society, including optical telecommunications, biophotonics, medical devices, optical sensors and materials processing, with a global market expected to reach €615 billion by 2020 and growing. Photonic sensors are a key element of the sector; measurement of molecular-specific optical transitions allows qualitative and quantitative analysis in-situ, without the need to chemically prepare or damage the sample in question, and hence is hugely attractive for a wide range of applications, from Process Analytical Technology (PAT) to biomedical diagnostics.

Due to Europe's strong activity in optical sensing and the large variety of applications, it is becoming increasingly difficult for all sectors to find highly skilled photonics graduates, particularly at the interfaces between sectors. In particular, optical sensing is intrinsically a multi-disciplinary topic, requiring expertise in chemistry, physics and engineering, making truly disruptive innovation difficult within a traditional Ph.D. project. The OPTAPHI network (pronounced opta-fy) aims to address this by training a cohort of doctoral students in the complementary fields of advanced spectroscopy and integrated optics. Specifically, the focus is on the methods of photo-acoustic and photo-thermal spectroscopy, and the compact semiconductor lasers and integration techniques that enable sensors based on these.

Within OPTAPHI, 14 Early Stage Researchers will be enrolled in Double Doctorate degree programmes, studying at, and being awarded Ph.D. degrees from, two of the partner institutes. The training from leading research groups will be complemented by secondment opportunities offered by ten associated Partner Organisations, together with network-wide training events such as workshops and a summer school. Overall scientific objectives include;
- Demonstrate novel Quartz Enhanced Photo-Acoustic Spectroscopy (QEPAS) and Photo-Thermal Spectroscopy (PTS) configurations with improved sensitivity and compactness
- Demonstrate improved detection of benzene, toluene, ethylbenzene and xylene (BTEX) and propane exploiting long wavelength 10+ μm laser sources
- Demonstrate highly sensitive Photo-Thermal Spectroscopy for liquid analysis for the first time Improve the compactness, robustness and power consumption of QEPAS to allow use on Unmanned Aerial Vehicles
- Demonstrate new methodologies to improve the sensitivity of PTS and QEPAS in the second overtone band, thereby allowing the use of low-cost telecoms components
The project kick-off meeting was held in Cork, Ireland in January 2020. Subsequently, an agreement on Double Degree programmes between the 5 partner institutes has been achieved, and all 14 Early Stage Researchers have been recruited; recruitment was via a centralised submission and assessment process. The COVID-19 pandemic has, of course, affected the project, with some delays in recruitment/relocation of ESRs, and the first Workshop, originally planned to be held in Montpellier, France, was instead held as an online event in April 2021. However, all the ESRs were able to attend in person at the Summer School, held in Erice, Sicily, Italy in October 2021. The School was held in conjunction with the International School of Quantum Electronics, with a total of 80 attendees.
Each Fellow has established a Personal Career Development Plan, and completed a 9-month progress review report. A project website was established at and a Twitter account, @optaphi. A number of flyers and a full 26-page prospectus were prepared as part of the recruitment advertising, and a pull-up banner was produced for use at events.
The scientific activities of OPTAPHI are grouped into three workpackages, with a team of Early Stage Researchers (ESRs) working on each. It should be noted that, while each ESR is nominally assigned to a particular WP, his/her project will generally have relevance and input to other WPs as well. The three technical workpackages are:

WP1: Environmental Sensing
The main goal of WP1 is the realisation of a portable demonstrator to showcase the potential of the OPTAPHI technologies for high-sensitivity detection of a number of gases important for the environment, such as BTEX, methane, CO, CO2, N2O, etc. Several different laser technologies and sensing approaches are being developed by 5 ESRs, including; compact diode-laser based QEPAS for UAVs; long-wavelength PTS for BTEX detection; hybrid photonic crystal lasers for intra-cavity QEPAS and PTS; Long wavelength QCLs for BTEX and propane detection through QEPAS; and generation and detection of photo-thermal and photo-acoustic waves in solids for advanced near-field IR imaging.

WP2: Agri-Food Analysis
The goal of this workpackage is the realisation of a shoe-box sized demonstrator PTS and/or QEPAS sensor capable of monitoring the quality of foods. As target gas analytes, basic amines (in particular ammonia) as an indicator for food degradation (fish) as well as diacetyl as a quality parameter for brewing have been chosen. The 4 ESR projects within WP2 are: ultra-compact QEPAS by integrating cantilever hybrid laser with quartz tuning fork; QEPAS and PTS using low-cost telecoms wavelength lasers for food analysis; High Q factor Photonics Cavities for PTS; and Intracavity PTS with optical feedback for isotopic verification of food origin.

WP3: Industrial Process Monitoring
The main goal of WP3 is the realisation of highly performant, innovative and compact sensing systems to be used for monitoring industrial processes. Sensing approaches like intra-cavity QEPAS for highly sensitive target gas measurements or PTS for detection of water in organic solvents will be developed. At the same time, improvement in the laser sources will be pursued by realising novel hybrid laser and single mode interband cascade lasers.

The ESRs have progressed well towards these targets, achieving different levels of maturity on both the laser and sensing aspects, depending on the starting TRL of the technology. This has included the design, fabrication and testing of a number of different laser devices, as well as building and optimising several lab-based spectroscopy setups. A total of 16 journal articles and 2 conference papers related to OPTAPHI have been published, including 2 papers with an OPTAPHI ESR as first author.
OPTAPHI Logo with dark background
OPTAPHI Logo with white background
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