CORDIS - Forschungsergebnisse der EU

TeraHertz detection enabled by mOleculaR optomechanics

Periodic Reporting for period 2 - THOR (TeraHertz detection enabled by mOleculaR optomechanics)

Berichtszeitraum: 2020-03-01 bis 2022-08-31

Generation, manipulation, and detection of electromagnetic waves across the entire frequency spectrum is the cornerstone of modern technologies, underpinning many disciplines such as sensing, imaging, spectroscopy and telecom networks. Whilst the last century has witnessed an impressive evolution in devices operating at frequencies either below 0.1 THz (microwave and antenna technology) or above 50 THz (near-infrared – NIR - and visible – Vis - optical technology), in between the lack of suitable materials and structures for efficient electromagnetic manipulation has resulted in the so-called “THz gap”: a band of frequencies in the ~0.1 – 30 THz region for which compact and cost-effective sources and detectors do not exist – even though their application has enormous potential in medical diagnostics, remote sensing, security, astronomy, and wireless communication. While coherent detection of waves in the 0.1 – 2.5 THz domain is now widely performed in the laboratory using ultrashort laser pulses and photoconductive antennae or other non-linear materials, these techniques are far from commercial applications due to their high complexity and cost. Recent advances in III-V Schottky diodes and field-effect transistors are closing the gap up to ~1 THz with some prospects for commercialisation,3 but the available techniques for direct detection in the 1-30 THz regime (micro-bolometer, Golay cells, pyroelectrics – all based on thermal effects) are slow, noisy and bulky. Clearly, a new concept for the detection of THz waves in this range would have dramatic impacts on THz technologies.

In THOR, we will demonstrate the first nano-scale, cost-effective, fast, and low-noise detectors working in the 1 – 30 THz range by developing a radically novel concept of signal up-conversion to visible/near-infrared (Vis/NIR) radiation, leveraging the latest scientific breakthroughs in the emerging field of molecular cavity optomechanics.

THOR’s impact on society and the economy will be achieved indirectly via the future development of molecular OM devices that will play a key role in several of the societal challenges addressed in H2020, e.g. in (i) Health, demographic change, and wellbeing; and (iii) Secure societies - protecting freedom and security of Europe and its citizens. In addition, THOR’s concept could be applied to improve Raman spectroscopy, thus playing a role in disciplines such as chemistry or biology.
Here, we summarize the work performed from the beginning of the project and main results achieved towards the achievement of the main THOR objective.

WP1. Molecules.
In WP1, we have developed an extensive study using DFT of the vibrational properties of more than 2000 molecules with the goal to maximize simultaneously the infrared absorption and the Raman activity of the molecules in the proposed range of the detector, by means of machine learning techniques. This has led to the timely achievement of Milestone MS1. We have also concluded that porphyrin ion based metallic complexes are promising candidates for the final device due to the presence of intense and well-defined low-energy Raman peaks, coincident with the range of energies targeted in the detector.

WP2. Cavities.
In WP2 we have studied hybrid plasmonic-dielectric cavities featuring high optical quality factors (Q) as well as low effective volumes (V) in order to boost the optomechanical coupling rate. We have also implemented a numerical simulation framework for hybrid cavity geometries as well as THz-to-SERS transduction metrics, which means that Milestone MS2 has been achieved. We have successfully measured SERS in hybrid cavities consisting of bowtie nanoantennas on SiN photonic crystal cavities. ). In addition, we have designed visible and telecom wavelengths hybrids based on the NPoM cavity and suitable for driving via waveguides showing Q > 103 and V ~ 3/104. Finally, we have developed ways to integrated metallic NPoM cavities with SiN waveguides demonstrating SERS as a previous step towards fully-integrated waveguide-driven detectors.

WP3. THz-to-optics molecular converter.
We successfully achieved a room-temperature, low-noise, coherent THz-to-optics converter based on a nanostructured silicon chip operating at 33THz. We developed a theoretical model that suggests operation with specific molecular layers can operate at 2-5THz. We also invented and patented a new way to provide the THz-to-optics conversion which operates at 33THz successfully, and are also testing this at 2-5 THz range. Another main result in WP3 is the fact that we can observe picocavities at room temperature in a regular fashion (achievement of MS4).

WP4. Management.
All administrative, legal and technical issues of the project have been properly managed. We have held three face-to-face meetings (AMOLF, CSIC and UPV partners) and many videoconferences. In the first meeting, the Project Management Committee (PMC) was formed. Since then, the PMC has efficiently managed all the technical aspects of the project. The coordinator has ensured an efficient communication between partners. The coordinator has also conveniently transferred to the partners the information coming from the Project Officer.

WP5. Dissemination and exploitation.
The Website was set-up ( and a logo was created, as detailed in Deliverable D5.1. The Website includes a private area where we have been uploading the documents generated by the different partners during the project. We have been updating the Website since its creation. The consortium developed a data management plan, which was explained in Deliverable D5.1. The plan for dissemination and exploitation has also been updated. We also formed the Industrial Advisory Committee (IAC), meeting with them in summer 2021 to identify ways to exploit the project results. A patent on the new method of detection have been filed.
THOR has demonstrated for the first time the frequency upconversion of electromagnetic signals from the IR to the visible spectrum mediated by molecular optomechanics, confirming our previous theoretical predictions.
We have built an open-access library (Molecular Vibration Explorer) with the IR absorption and Raman response of multiple molecules.
We have developed the technology to integrate NPoM cavities with silicon nitride waveguides towards integrated SERS and, ultimately, integrated molecular-based THz detection.
We have advanced in the development of hybrid photonic-plasmonic cavities, with new waveguide-driven designs using NPoM cavities as well as the experimental demonstration of SERs in hybrid bowtie cavities.
We have unveiled a new detection technique (MIR-VAL), which has been patented and shows interesting features for industrial development.
Sketch of the THOR device