Monolithic frequency comb spectrometers

Project Information

MonoComb

Grant agreement ID: 853014

DOI

10.3030/853014

Project closed

EC signature date 10 December 2019

Start date 1 February 2020

End date 31 January 2025

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 1 498 230,00

EU contribution

€ 1 498 230,00

Coordinated by

TECHNISCHE UNIVERSITAET WIEN
Austria

Periodic Reporting for period 4 - MonoComb (Monolithic frequency comb spectrometers)

Reporting period: 2024-08-01 to 2025-01-31

Summary of the context and overall objectives of the project

Optical frequency combs are powerful tools for precision spectroscopy, enabling highly accurate measurements across a broad range of light frequencies. In the mid-infrared spectral region, many biologically relevant molecules have distinct absorption fingerprints. One promising application is breath gas analysis, where mid-infrared spectroscopy can detect trace biomarkers linked to diseas-es such as diabetes, cancer, and respiratory conditions. This non-invasive diagnostic approach has the potential to revolutionize early disease detection and patient monitoring. In order to widely use the potential of mid-infrared spectroscopy for biomedical applications, large datasets are required, necessitating the deployment of numerous compact and cost-effective sensors.
The goal of the MonoComb project was to establish the foundation for these sensors by bringing bring dual-comb spectroscopy onto a single chip using integrated photonics in the mid-infrared. By developing a compact and scalable technology, MonoComb aims to enable the next generation of single-chip spectrometers, making mid-infrared photonics more accessible for their widespread application.
MonoComb addressed several key scientific and technological challenges. It involved the develop-ment of accurate and predictive simulation tools for frequency comb operation and the exploration of new methods for frequency comb generation in integrated devices based on quantum cascade lasers and interband cascade lasers. In addition, the project tackled technological challenges relat-ed to the miniaturization of optical gas sensors and worked on the development of low-loss on-chip integrated waveguides for optimal on-chip light-gas interaction. These efforts led to the demonstration of prototype dual-comb sources and sensors, marking a significant step toward practical on-chip dual-comb spectrometers. By advancing the theoretical understanding and tech-nological development of mid-infrared integrated photonics, MonoComb has established a strong foundation for future research and innovation, paving the way for compact, high-performance spectrometers for biomedical and environmental applications.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The MonoComb project focused on advancing on-chip dual-comb spectrometers, combining exper-tise in multimode laser dynamics, semiconductor fabrication, and photonic integration. We achieved major milestones, including publishing 30 peer-reviewed articles in prestigious journals, including Nature and Physical Review Letters, completing four doctoral dissertations, and three master's theses so far.
Key achievements include developing a sophisticated cavity model to simulate the behavior of mul-timode lasers, which led to critical insights into quantum cascade laser (QCL) frequency combs and their potential for sensing applications. Our new characterization technique allowed direct meas-urement of giant nonlinearities in QCLs.
We also made significant strides in laser technology, such as emitting picosecond pulses at room temperature using a QCL, and uncovering new findings on Interband Cascade Lasers (ICLs), which improved our understanding of their temporal behavior and led to new strategies for pulse genera-tion. A major breakthrough was the generation of Nozaki-Bekki solitons within semiconductor ring lasers, culminating in the creation of a monolithic semiconductor laser chip capable of generating bright solitons with suppressed feedback sensitivity and proven stable operation—paving the way for advancements in mid-infrared spectroscopy and chemical sensing.
Our work on miniaturization and on-chip integration led to the development of new platforms for integrated frequency combs and explored novel integration approaches to combine them with integrated waveguides for chemical spectroscopy. In terms of real-world applications, we devel-oped prototype sensors for isotope-sensitive CO2 detection and for monitoring residual water con-centrations in solvents, showcasing the practical potential of our technological advancements in the field of integrated photonics.
These breakthroughs set the stage for further innovations in laser systems and their application in sensitive, energy-efficient sensing technologies.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The MonoComb project has advanced the frontiers of integrated photonics, mid-infrared lasers, and ultrafast pulse generation, achieving key breakthroughs in frequency comb generation, soliton dynamics, and sensor miniaturization. These developments have led to more compact, efficient, and scalable laser technologies with broad applications in mid-infrared spectroscopy.
One of the most significant achievements has been the discovery of how Bloch gain induces giant Kerr nonlinearity in quantum cascade lasers (QCLs). This giant nonlinearity, predicted theoretically and confirmed through novel characterization techniques, has provided crucial insights into the nonlinear dynamics governing QCLs.
Building on these advancements, the project demonstrated the first mode-locked short pulses from a quantum cascade laser operating at room temperature and emitting at a wavelength of 8 μm—overcoming a long-standing challenge in mid-infrared ultrafast photonics. By precisely engineering the quantum gain medium and controlling intermode beat synchronization, transform-limited pico-second pulses were achieved. Furthermore, MonoComb has driven pioneering work in soliton dy-namics, including the realization of Nozaki–Bekki solitons in semiconductor ring lasers and the de-velopment of the first monolithic, DC-driven laser chip capable of generating bright solitons. These breakthroughs represent a major step toward compact, stable, and integrated photonic devices for high-precision sensing and spectroscopy applications.
These results have been published in prestigious journals such as Nature and Physical Review Let-ters, reaching a broad scientific audience and highlighting the significance of these advancements. These technological breakthroughs lay the foundation for further research and development, driv-ing continued progress toward on-chip mid-infrared spectrometers through future research grants and collaborations.

sketch of a QCL frequency comb