Coherent Sensing
Welcome to our group website!
Our work is dedicated to high resolution spectroscopy with frequency combs and coherent sensing. We use ultrashort laser pulses on the femtosecond time scale to learn more about the optical properties and transient dynamics of atoms and molecules, so far mostly in the gas phase. Recently, we have extended our research focus to applications of photochemical and biophysical relevance.
From left to right: Elias Ehl, Birgitta Schultze-Bernhardt, Christoph Gruber, Mithun Pal, Johannes Spendier
(missing on the photo: Armin Speletz).
Birgitta Schultze-Bernhardt, Mithun Pal, Christoph Gruber.
Figure 1: Comparison of ultraviolet absorption cross section measurements in formaldehyde a DCS absorption cross section spectrum of HCHO (blue, above the abscissa) compared to previous measurements (see details in [10]). The spectrum was recorded at T = 294 K, p(HCHO) = 90 mbar, with an optical path length of 310 cm and an acquisition time of 0.5 s. b & f The strong absorption features of both traces agree qualitatively but display minor differences in the line positions. c & g The DCS spectrum has an up to 20 times lower noise level, despite a substantially shorter acquisition time (0.5 s for DCS versus 60 min). d, e & h, i For frequencies above 853 THz, the DCS trace resolves the rovibronic lines for the first time. The mean relative absorption cross section uncertainty amounts to 7.2%. Figure taken from [10].
Further recent works of the coherent sensing group:
- Streaming Dual Comb Spectroscopy in Real-Time: Eber, A., Gruber, C., Schultze, M., Bernhardt, B., Ossiander, M., Streaming self-corrected dual-comb spectrometer. Optics Express 33: 35314–35325 (2025), https://doi.org/10.1364/OE.569404
- Systematic Comparison of dual comb spectroscopy with different repetition rate regimes: NIR/VIS dual-comb spectroscopy comparing high and low repetition rate regimes. A Eber, M Pal, L Fürst, E Hruska, C Gruber, M Ossiander, B Bernhardt; Laser & Photonics Reviews, e02713 (2026)
- Together with the Leonahrd Grill Group, Uni Graz: : Switching Azobenzene Derivatives on Au(111) Analyzed by Advanced Computer Vision Methods, Matthew James Timm; Alexander Eber; Emily Hruska; Stefan Hecht; Leonhard Grill; Birgitta Bernhardt, Surface Science, 122971 (2026) https://doi.org/10.1016/j.susc.2026.122971
- Resonant dispersive-wave frequency comb generation: Kirchner, A., A. Eber, L. Fürst, E. Hruska, M. H. Frosz, F. Tani, and B. Bernhardt (2025). Ultra-broadband UV/VIS spectroscopy enabled by resonant dispersive wave emission of a frequency comb, Optics Express, 33, 7005–7015 (2025), https://doi.org/10.1364/OE.546751
This research is funded the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement no. 947288), by the Austrian Science Fund FWF START program (grant agreement no. Y1254N) and the NAWI Graz infrastructure funding program.
June 3rd 2026
TU Graz Physicist Presents Mobile Device for High-Precision Measurement of Air Pollutants
The UV dual-comb spectrometer detects harmful gases with unrivalled accuracy and sensitivity. The compact design allows mobile use for monitoring air quality with a range of several kilometres.
March 20th 2026
New Paper Out!
Our frequency combs have entered the fascinating world of Surface Science!
So far, our combs enabled "just" superior spectral resolution. In our most recent work, one of our combs helped to shed light onto the complex switching behavior of azobenzene molecules - with single molecule resolution. Special thanks go to our Coherent Sensing team mate Robert di Vora for his powerful computer vision algorithm and to Matthew Timm and Leonhard Grill for introducing us to their STM realm!
Check out our joint publication in Surface Science: https://doi.org/10.1016/j.susc.2026.122971
#FrequencyCombs #ERCStartingGrant #CoherentSensing
January 15th 2026
New Paper Out!
Our work on NIR/VIS dual comb spectroscopy with low and high repetition rate regimes is published in Lasers & Photonics Reviews!
In this paper, we have compared two dual comb systems operating at 80 MHz and 1 GHz repetition rates. Both have their advantages - depending on the envisioned applications
check out the details here:
12th October 2025
Our research at FÄKT!
This time, we were visited by Julia and the FÄKT team and had a great time showcasing our lasers in action!
How do our measurements actually work, and what are we discovering about the air quality in Graz?
FÄKT is a science communication project by the Austrian Academy of Sciences (ÖAW), aimed especially at a young audience. Curious? Then check out the result from Graz here:
14th July 2025
Measuring Air Pollutants in Real Time: ERC Proof of Concept Grant for TU Graz Physicist
Birgitta Schultze-Bernhardt receives funding from the European Research Council for the development of a portable device that measures several pollutants simultaneously in a fraction of a second.
TUG Pressemitteilung
June 18th 2025
RIGOROSUM
Adrian KIRCHNER
Agile frequency upconversion for ultra-broadband dual comb spectroscopy across the visible and ultraviolet spectral regions
Adrian Kirchner successfully defended his doctoral thesis „ Agile frequency upconversion for ultra-broadband dual comb spectroscopy across the visible and ultraviolet spectral regions“ on June 18th 2025. We could invite our collaboration partner Prof. Arnaud Mussot, University of Lille, to Graz as second reviewer who is an expert on EOM frequency combs including all-fiber frequency agile triple-frequency comb light sources.
Congratulations, Adrian!
May 5th 2025
New Paper Out!
Our work on a phase locked feed forward stabilization scheme for dual comb spectroscopy is published in Ultrafast Science Journal.
It improves our existing IR/VIS dual comb spectrometer operated at 80 MHz in terms of spectral resolution (three orders of magnitude) and sensitivity (one order of magnitude). For our NO2 field measurements, this means an improved detection limit down to 1 ppb!
Check it out:
Phase-Locked Feed-Forward Stabilization for Dual-Comb Spectroscopy | Ultrafast Science
Special thanks go to Marcus Ossiander for the inspiring team work!
Lab Fotos
