Coherent Sensing

Welcome to our group website!

Our work is dedicated to laser spectroscopy and coherent sensing.  We use ultrashort laser pulses on the femtosecond time scale to learn more about the optical properties 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.

Coherent Sensing Group in October 2023
From left to right: Florian Lindorfer, Robert Di Vora, Armin Speletz, Mithun Pal, Birgitta Schultze-Bernhardt, Emily Hruska, Lukas Fürst, Alexander Eber, Elias Ehl, Adrian Kirchner. Not on the picture: Kevin Nusshold.


1. Dual comb spectroscopy in different spectral regions

Dual Comb Spectroscopy combines high spectral resolution with broad spectral coverage and short measurement times. In the recent years, this spectroscopic method has proven its capabilities in molecular spectroscopy in different spectral regions ranging from the visible across the infrared spectral region into the THz domain, see for example [1-3]. We are currently expanding dual comb spectroscopy for different applications ranging from the detection of unknown gas mixtures to Raman spectroscopy for the examination of biophysical samples [2].

2. Electronic Fingerprint Spectroscopy

So far our knowledge about (extreme) UV characteristics of atomic and molecular gasses and condensed matter is scars due to the lack of readily available laser sources in this spectral region. Especially high resolution spectroscopic studies with an advanced relative spectral resolution on the order of 10-5 and 10-6 still have to be performed at synchrotron sources that are only restrictedly accessible. In the recent years, the high power laser technology has prospered such that table top high photon flux (X)UV sources with high repetition rates become possible not only with enhancement cavities [4] but also in single pass geometry. However, laboratory XUV spectroscopic studies are still limited by conventional grating spectrometers that typically provide a spectral resolution on the order of 10-3 [5,6].  At the IEP, we are currently developing the world`s first UV dual comb spectrometer that will enable an unparalleled relative spectral resolution of up to 10-9 outperforming synchrotron-based spectrometers by up to three orders of magnitude (see figure 1) and grating based XUV spectrometers by even up to six orders of magnitude [7].

Recently, we have developed a mobile dual comb spectrometer operating in the visible spectral region that we used for field monitoring of NO2 in the city of Graz [8]. The world’s first broadband NUV dual comb spectrometer enabled the simultaneous detection of rovibrational states in formaldehyde and real time monitoring of this environmentally highly relevant pollution gas [9].

This research is funded the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement no. 947288) and by the Austrian Science Fund FWF START program (grant agreement no. Y1254N).

Figure 1

Figure 1: Extreme Ultraviolet (XUV) Dual Comb Spectroscopy yielding ultra-broadband (>150 THz) absorption spectra of atoms and molecules with an unparalleled spectral resolution on the order of µeV. This resolution is hitherto unprecedented for XUV table top sources but mandatory for example for the resolution of high principal quantum numbers in Rydberg series (the example shows the Rydberg series in argon converging against the ionization limit at 15.76 eV).

Bachelor, Master and PhD theses
For potential projects in the field of laser spectroscopy, please contact

Visit our lab virtually via YouTube (in German):

Recent news

April 10th 2024

Our novel broadband UV dual comb spectrometer becomes official!

Congratulations, Lukas!

The world’s first broadband UV dual comb spectrometer revolutionizes air pollutant analysis. It enables real-time tracking of pollutants and their reactions with the environment. The work got now published in OPTICA.

Check out more details
Press release:
Novel UV Broadband Spectrometer Revolutionises Air Pollutand Analysis

Broadband near-ultraviolet dual comb spectroscopy

NAWI Graz, Kooperation zwischen TU Graz und KF Universität Graz
© Lunghammer

Febraury 12th 2024

The work of our first field deployed dual comb spectrometer got published!

Congratulations, Alex!

We successfully tracked the concentration of nitrogen dioxide in the city of Graz. We achieved a temporal resolution of one minute and a detection sensitivity of only 5 ppb.
To our knowledge, this is the first mobile dual comb spectrometer capable of measuring NO2.

Check out more details:
Coherent field sensing of nitrogen dioxide (

Febraury 8th 2024

Dual Poster Presentation on Dual Comb Spectroscopy

Armin and Elias show their posters in parallel on this year`s first DocDay!

January 29th 2024

Coherent Sensing Group meets Anne L’Huillier

Group Excursion to the Austrian Academy of Sciences (ÖAW) in Vienna for this year’s ISTA Lecture:
Anne L’Huillier talked about “Attosecond Pulses For Studying Ultrafast Electron Dynamics”. The most important step towards attosecond pulses is high harmonic generation that has been studied extensively by Anne L’Huillier and that plays also a crucial part in our Project ELFIS, funded by the ERC.

January 26th 2024

Coherent Sensing Group visits Ball der Technik

Part of the team entered “one of the nicest balls of Austria”!

September 2023

Elias EHL joins our team


Herzlich Willkommen, Elias!

September 2023

Emily HRUSKA joins our team


Herzlich Willkommen, Emily!

July 2023

Mithun PAL joins our team


Herzlich Willkommen, Mithun!

June 2023

Coherent Sensing Group in June 2023

From left to right: Robert Di Vora, Adrian Kirchner, Birgitta Schultze-Bernhardt, Lukas Fürst, Armin Speletz, Alexander Eber. Not on the picture: Kevin Nusshold.

May 2023

Armin SPELETZ joins our team


Herzlich Willkommen, Armin!

April 2023

Group Excursion to the Austrian Academy of Sciences (ÖAW) in Vienna: The German Physical Society (DPG) and the Austrian Physical Society (ÖPG) organized this year`s Lise Meitner Lecture with the ÖAW. Donna Strickland shared her insights and experiences with quite different aspects of chirped pulse amplification in her talk on “Generating High-Intensity, Ultrashort Optical Pulses”.

Event link:

From left to right: Lukas Fürst, Alexander Eber, Birgitta Bernhardt, Adrian Kircher, Robert Di Vora, together with Archduke Rainer Ferdinand from Austria.
Donna Strickland talking about her first struggles with high harmonic generation.

October 2022

With the start of my university professorship, we are expanding our research focus as Coherent Sensing group to applied environmental sciences including atmospheric monitoring, trace gas sensing and the investigation of novel materials for photo-voltaics.

Stay tuned for the latest developments, open positions or contact me directly:

October 2022

Robert DI VORA joins our team


Herzlich Willkommen, Robert!

Juni 2022

Adrian KIRCHNER joins our team


Herzlich Willkommen, Adrian!

April 2022

"Wie man mit Lasern fotografiert"

Read about our latest research projects in our contribution to the
ÖAW Junge Akademie Blog @ DER STANDARD

February 2022

First NUV Dual Comb Spectroscopy

Lukas Fürst optimizing his first interferogram, produced by two interfering near-ultraviolet frequency combs.

If you are interested in older news, visit our "News Archive"!

Lab Fotos

Dual Comb Lab
Dual Comb Lab
Dual Comb Spectrometer operating in the visible spectral region
Iodine Cell
NIR-VIS Dual Comb Spectrometer

Selected Publications

[1] B. Bernhardt, A. Ozawa, P. Jacquet, M. Jacquey, Y., T. Udem, R. Holzwarth, G. Guelachvili, T. W. Hänsch and N. Picqué, Cavity-enhanced dual-comb spectroscopy, Nature Photonics 4, 55-57 (2009)

[2] T. Ideguchi, S. Holzner, B. Bernhardt, G. Guelachvili, N. Picqué and T. W. Hänsch, Coherent Raman spectro-imaging with laser frequency combs, Nature 502, 355 (2013)

[3] T. Ideguchi, B. Bernhardt, G. Guelachvili, T.W. Hänsch and N. Picqué, Raman-induced Kerr-effect dual-comb spectroscopy, Optics Letters, Vol. 37, 4498 (2012)

[4] B. Bernhardt, A. Ozawa, A. Vernaleken, I. Pupeza, J. Kaster, Y. Kobayashi, R. Holzwarth E. Fill, F. Krausz, T. W. Hänsch, and Th. Udem, Vacuum ultraviolet frequency combs generated by a femtosecond enhancement cavity in the visible, Optics Letters 4, 503 (2012)

[5] B. Bernhardt, A. R. Beck, X. Li, E. R. Warrick, M. J. Bell, D. J. Haxton, C. W. McCurdy, D. M. Neumark and S. R. Leone, High-spectral-resolution attosecond absorption spectroscopy of autoionization in xenon, Physical Review A 89, 023408 (2014)

[6] K. Hütten, M. Mittermair, S. Stock, R. Beerwerth, V. Shirvanyan, J. Riemensberger, A. Duensing, R. Heider, M. Wagner, A. Guggenmos, S. Fritzsche, N. M. Kabachnik, R. Kienberger and B. Bernhardt, Ultrafast Quantum Control of Ionization Dynamics, Nature Communications 9, 719 (2018)

[7] V. Schuster, C. Liu, R. Klas, P. Dominguez, J. Rothhardt, J. Limpert, and B. Bernhardt, Ultraviolet dual comb spectroscopy: a roadmap, Optics Express 29, Issue 14, 21859-21875 (2021)

[8] A. Eber, et al., Coherent field sensing of nitrogen dioxide, Opt Express 32, 6575 (2024)

[9] Fürst, Lukas, et al., Broadband near-ultraviolet dual comb spectroscopy, Optica 11.4, 471-477 (2024)


All images © TU Graz/Institute of Experimental Physics

Institut of Experimental Physics
Graz University of Technology
Petersgasse 16
8010 Graz

Group Leader
Univ.-Prof. Dipl.-Phys. (Univ.) Dr.rer.nat.

Tel.: +43 (0) 316 / 873 - 8663
Fax: +43 (0) 316 / 873 - 8655

Group Members

Univ.-Prof. Dipl.-Phys. (Univ.) Dr.rer.nat. Birgitta BERNHARDT
Curriculum Vitae
+43 (316) 873-8663

BSc DI Alexander EBER
+43 (316) 873-8152


+43 (316) 873-8928


+43 (316) 873-8147

+43 (316) 873-8146




BSc MSc Ph D. Mithun PAL


+43 (316) 873-8662

BSc MSc Elias EHL
+43 (316) 873-8662