Optica has elected Pascal Del’Haye a Fellow of the class of 2027. The society recognises his pioneering work on microresonator-based frequency comb generation and his contributions to nonlinear microphotonics and optical symmetry breaking. Congratulations, Pascal!
We turn one colour of light into many, on a chip.
We study how light behaves when it circulates in microscopic ring resonators. Our chips are designed, fabricated and measured in our own cleanroom at the Max Planck Institute for the Science of Light in Erlangen.
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We welcome Luiz Peres, who joined the group in October 2026 for a nine-month research stay. Luiz is a PhD student in the group of Gustavo Wiederhecker at the Gleb Wataghin Physics Institute of the University of Campinas (Unicamp), Brazil, where he also completed his BSc and MSc. In his Master’s work he simulated photonic integrated circuits for single-photon quantum information processing, studying Bell and contextuality inequalities with meshes of Mach-Zehnder interferometers. His PhD work focuses on the generation of squeezed light in ring resonators, including the design of coupled-resonator systems. During his visit at MPL he extends his studies to multi-mode squeezing in microcombs.
Congratulations to Arghadeep Pal, who successfully defended his PhD thesis Tailoring Optical Fields for Nonlinear Photonics in Microresonators at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) on 16 September 2026! During his PhD, Arghadeep worked on machine-learning-assisted inverse design of microresonators, linear and nonlinear coupling of light in twin resonators and hybrid nonlinear effects in photonic integrated circuits, the work that also won him the best poster award at the MPSP Spring School earlier this year.
Our best wishes to Arghadeep for the next steps!
In a silicon nitride ring resonator embedded in silica, the light uses both materials at once: Raman scattering in the silica cladding and four-wave mixing in the silicon nitride core together produce broad frequency combs spanning more than 400 nm. Arghadeep Pal, Alekhya Ghosh and colleagues report the results in Advanced Photonics.
➔ Advanced Photonics 8, 046008 (2026)
Together with Kiyoul Yang’s group at Harvard, Toby Bi and colleagues used inverse design to create silicon nitride chip components that are up to 500 times smaller than conventional ones. Instead of adjusting familiar shapes by hand, the algorithm starts from what the light should do and searches for a nanostructure that does it.
➔ Nature Communications 17, 6943 (2026)
We have two postdoc positions available. Research topics include microcombs, neuromorphic computing, chip based quantum light states, nonlinear optics, optical clocks and microfabrication of photonic chips in our in-house cleanroom.
If you are interested and have a research background in these topics, please get in touch with your CV.
We are part of ResonaTHOR, a European consortium funded through QuantERA and coordinated by TU Wien, which works towards a compact nuclear clock based on thorium-229. Our group designs, fabricates and characterises the high-quality resonators that enhance the interaction between light and the thorium nuclei.
Congratulations to Alekhya Ghosh on successfully defending the PhD thesis Kerr-Nonlinearities and Symmetry Breaking in Microresonators at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) on 20 July 2026! Alekhya’s work explored how the Kerr nonlinearity breaks the symmetry between light fields in coupled and counter-propagating microresonators, from four-field symmetry breaking in twin-resonator photonic isomers and controlled light distribution in coupled microresonator chains to phase symmetry breaking for optical switches and logic gates.
The celebration came with the traditional doctoral hat and a cart decorated with photos from the past years. Alekhya has since joined Kartik Srinivasan’s Nanophotonics for Quantum Science group at the Joint Quantum Institute (JQI), University of Maryland, as a postdoc. Congratulations, Alekhya, and all the best in Maryland!
Check out our new microcomb simulator and play around with dispersion, detuning and power. Microcomb Simulator
Congratulations to Abdullah for the best poster award for “Visible Octave Comb Generation” at the Winter School on Nonlinear Photonics in Italy. Read more
Our group successfully finished a laserhandling course, including evasion of laserbeams and extremely fast laser alignment :)
Congratulations to Haochen Yan, who successfully defended his PhD thesis at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) on 21 April 2026! His thesis, Visualization of intra-cavity dynamics of high-quality factor microresonators, is about making visible what light does inside a microresonator. Highlights of his PhD include the real-time imaging of standing-wave patterns in microresonators (PNAS) and a simplified aluminium nitride process for low-loss integrated photonics and nonlinear optics.
After the defense, Haochen received the traditional doctoral hat, decorated with highlights from his research. He has since moved on to a position as research scientist at OptQC. We wish Haochen all the best for the next steps!
Congratulations to Arghadeep Pal for winning the best poster award at the 2026 Spring School of the Max Planck School of Photonics (MPSP) in Berlin. His poster showed how hybrid nonlinear effects in photonic integrated circuits enable Raman comb generation in silicon nitride microresonators. Read more: Advanced Photonics 8, 046008 (2026).
In the project ALP-4-SiC, funded by the German Federal Ministry of Research, Technology and Space, we work with Fraunhofer IISB on silicon carbide photonic circuits for quantum technologies. Atomic layer processing smooths the surfaces of waveguides and ring resonators and clearly improves their optical performance.
We present optical switch and photonic logic gates utilizing phase changes of optical fields arising from Kerr interactions.
Laser & Photonics Review, e01500 (2025).
Our paper on ultralow loss silicon nitride integrated photonics using room-temperature reactive sputtering has ranked within the top 10% of most-viewed papers published by Laser & Photonics Review in 2023. Laser & Photonics Review, 2300642 (2023) - arXiv:2301.10758.
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Shuangyou is awarded a DFG grant on Low-Temperature Sputtered Silicon Nitride for Integrated Photonic Applications, together with Pascal. The project will fund a PhD position for 3 years, offering an outstanding opportunity to contribute to cutting-edge research at MPL.
We report a novel approach for on-chip optical switches based on the first experimental demonstration of spontaneous symmetry breaking in high-Q Si3N4 resonators. This can be used for the implementation of on-chip optical memories and optical gyroscopes.
Photonics Research 13, 360 (Editor’s pick!)
We investigate broadband dispersion engineering in microresonators by incorporating nanostructures along the sidewalls of ring resonators. This can be used for broadband frequency comb generation.
Photonics Research 13, 367
Our research group was very involved in the filming of “Tracing Light”. The film explores light in many facets between art and science. It will be shown in cinemas across Germany starting Jan 16th 2025.
Tracing Light Infos
Official Trailer
The new book “Optical Frequency Combs - Trends in Sources and Applications” has been published. It includes a chapter from our group on microresonator frequency combs.
https://doi.org/10.1201/9781003427605
Our new paper about linear and nonlinear coupling of light in twin-resonator systems with Kerr-nonlinearities has been published. This can lead to real-time dispersion engineering, and active light distribution in telecom systems.
Photonics Research 12, 2733
Our new paper about light distribution patterns in chains of microresonators has been published. This can be used to guide light through photonic circuits and for optical data processing.
Photonics Research 10, 2376 (Editor’s pick!)
We demonstrate a new method for Hz-level spectroscopy with a scanning diode laser. Instead of using a frequency comb, this method relies on adding modulation sidebands to the scanning diode laser and linking it on-the-fly to a reference cavity.
Advanced Photonics 6, 046003
SPIE News Article
Our group will be at Optica Advanced Photonics Congress in Québec, Canada from July 28th to August 1st and present our research projects in 9 talks.
Link to conference program
Lewis Hill, senior scientist in our group, has been elected chair of Optica’s technical group for Nonlinear Optics, the largest of the society’s technical groups with around 4,000 members. He holds the position until 2027.
Our new PNAS paper presents the observation of controlled standing wave patterns that can be used for precise distance measurements with nm-accuracy. PNAS 121 (10) e2313981121, arxiv.
Our paper on ultralow loss silicon nitride integrated photonics using room-temperature reactive sputtering was published in Laser & Photonics Reviews. Our study demonstrates the lowest propagation losses achieved with a low temperature deposition method. It is CMOS compatible and can be used for hybrid integration with other photonic and electronic processes. Laser & Photonics Review, 2300642 (2023).
Our new paper titled “Geometry optimization for dark soliton combs in thin multimode silicon nitride microresonators” was published in Optics Express, which provides insights into engineering a Si3N4 structure for optimal effective nonlinearity with a compact footprint. We experimentally demonstrate the low-noise dark pulses with a repetition rate of 25 GHz in a Si3N4 resonator. Read more: Optics Express 31, 41420-41427 (2023).
Our paper on quintic soliton paper has been selected as the cover article in laser & photonics review. Our study demonstrates the first observation of solitons induced by fifth-order dispersion. Read more: Laser Photonics Rev., 2300075 (2023).
Our new paper on four-field symmetry breakings in photonic dimers has been published in Physical Review Research. This work demonstrates multi-level symmetry breakings, switching and chaos. Read more: Phys. Rev. Res. 5,L042012 (2023).
Our group will be at CLEO Europe in Munich from June 26th to June 30th and present our research projects in 9 talks.
Link to conference program
Our new paper on quintic-dispersion microresonator solitons has been published in Laser & Photonics Review. Our study demonstrates the first observation of solitons induced by fifth-order dispersion. Read more: Laser Photonics Rev., 2300075 (2023).
Congratulations to Arghadeep Pal for winning the best poster award at the spring school-2023 organised by the Max Planck School of Photonics (MPSP). The poster describes Machine Learning assisted prediction of microresonator structure for desired dispersion profiles. Read more: Opt. Express 31, 8020-8028 (2023).
We have used machine learning algorithms to predict structures of microresonators from dispersion profiles. This work lays the foundation of application of machine learning in inverse design of microring resonators.
https://doi.org/10.1364/OE.479899 - arXiv
Our new paper on optical light plateaus in microresonators has been published. This work has been done in collaboration with Gian-Luca Oppo and Graeme Campbell at the University of Strathclyde in Glasgow. https://doi.org/10.1103/PhysRevA.106.043507 - arXiv
We will be presenting at the upcoming CLEO conference in San Jose, California (15-20 May):
Lewis Hill, “Nested spontaneous symmetry breaking” 17 May
Shuangyou Zhang, “Dark-Bright Soliton Frequency Combs” 18 May
Leonardo Del Bino, “All-optical Kerr Polarization Controller” 19 May
Our new paper on bound states of dark and bright solitons in microresonators has been published in PRL. This can be used to broaden frequency combs across different dispersion regimes.
➔ Physical Review Letters, 128, 033901
Together with colleagues from Switzerland, Germany and the UK we have demonstrated a polarization controller that is operated purely by light using the Kerr-effect.
➔ Nature Communications, 13, 398
Our work on Kerr-effect enhancement of the rotation sensitivity of microresonator gyroscopes has been published in Optica.
➔ Optica 8, 1219-1226
A great interview with Shuangyou Zhang about his Marie Curie Multiply Fellowship. His work on low power microcombs was one of the top-downloaded frequency comb papers of the last years in Optica. Read more here: bit.ly/3sdENFy
We report the experimental and numerical observation of oscillatory switching between counter-propagating light beams in Kerr ring microresonators. This effect well captured by a simple coupled dynamical system featuring only the self- and cross-phase Kerr nonlinearities. Self-switching of counterpropagating light is robust for realizing controllable, all-optical generation of waveforms, signal encoding, and chaotic cryptography. Phys. Rev. Lett. 126, 043901
We demonstrate how the Kerr nonlinearity can be a key enabler for many digital photonic circuits. It allows access to bistable states needed for all-optical memories and switches that can operate at a single laser frequency with no additional electrical power. Opt. Express 29, 2193-2203 (2021)
We demonstrate a technique for suppressing backscattered light in a whispering-gallery-mode resonator by positioning a sub-wavelength-size scatterer within its evanescent field, achieving at least 34 dB suppression compared to the intrinsic backscattering. Read more: Light Sci Appl **9,**204 (2020).
Broadband frequency combs are a key enabling technology for frequency metrology and spectroscopy. Here, we demonstrate that the spectrum of a soliton microcomb can be extended by bi-chromatic pumping resulting in two combs that synchronize their repetition rate via cross-phase modulation. Read more: Nat Commun **11,**6384 (2020)
Toby recently visited Airbus Defence and Space to perform R&D experiments on advanced space optics components. The visit was a collaboration between Airbus and the Max Planck Institute for the Science of Light through the Horizon 2020 MICROCOMB network.
Congratulations to Andreas Svela for winning a prize for his talk at the Imperial College Faculty of Natural Sciences research showcase. The showcase presentation is aimed at a broader audience, explaining the backscatter suppression work published in Light Sci Appl9,204 (2020). Watch the Presentation here.
Our group will be presenting our most recent research results at the FiO-LS virtual conference. All our talks are on Wednesday 16 September (CET times).
- 14:30 George Ghalanos “Splitting of Microresonator Modes with the Kerr-Nonlinearity”
- 21:00 Niall Moroney “Microresonator Logic Gates”
- 02:30 (17 Sept) Shuangyou Zhang “Spectrally Extended Microcombs with an Auxiliary Laser”
Our paper on the direct measurement of the mode splitting induced by the Kerr effect has been published in Physical Review Letters. Phys. Rev. Lett. 124, 223901
Congratulations to Leonardo for passing his (virtual) PhD viva! Thanks also to his examiners and co-supervisors Derryck Reid, Frank Vollmer, and Marcello Ferrera.
Our paper on logic gates Based on Interaction of Counterpropagating Light in Microresonators has been published in Journal of Lightwave Technology. J. Lightwave Technol. 38, 1414-1419
Since January 2020, Pascal Del’Haye leads the new Microphotonics Research Group at the Max Planck Institute for the Science of Light in Erlangen. The group studies nonlinear optics in whispering-gallery-mode microresonators, frequency combs on a chip, and the interaction of counterpropagating light for optical diodes, gyroscopes and switches.
Our paper on the effects of self- and cross-phase modulation on the spontaneous symmetry breaking of light in ring resonators has been published in Physical Review A. Phys. Rev. A 101, 013823
I am happy to announce that our research will move to the Max Planck Institute for the Science of Light in January 2020.
Our paper on the generation of stabilized THz-waves with a soliton microcomb has been published in Optics Express. https://doi.org/10.1364/OE.27.035257
Lewis Hill received the “Conference Stand-out Presentation”-Award at this year’s Institute of Physics CAPS conference in Swansea. Congratulations Lewis!
Together with Alessia Pasquazi’s group at the University of Sussex we published a paper on thermo-optical pulsing in a nested microresonator system embedded in a ring laser. Optics Express 27, 19242-19254
Andreas Svela won the prize for the best student talk at the International Nanophotonics Summerschool at AMOLF for his talk on “Near-field sensing with symmetry-breaking enhancement in microresonators”. Congratulations Andreas!
We demonstrate a new technique to passively stabilize microresonator modes using an auxiliary laser. This enables the generation of soliton frequency combs at a record low threshold power of 780 microwatt. Optica 6, 206-212 Press release
Our recent work on the interplay between time-reversal symmetry breaking and polarization symmetry breaking has been published in Physical Review Letters. PRL 122 013905 Press release.
Together with our collaborators Michael Vanner and Georg Enzian from Imperial College we published a paper on Brillouin optomechanical strong coupling in microresonators. Optica 6, 7-14 (2019) Press release
Our paper on the dynamics of the interaction of counterpropagting light in microresonators has been published. This work has been done together with Gian-Luca Oppo and Lewis Hill at the University of Strathclyde. Physical Review A, 98, 053863
We are organizing a special symposium on nonreciprocal photonics at CLEO2019 in San Jose (May 5th-10th 2019). Contributed submissions welcome! More information on the CLEO website.
Our work on nonlinear interaction of counterpropagating light in microresonators received the 2018 NPL Rayleigh Award. Congratulations to everyone!
Our work on microresonator-based optical isolators and circulators using the nonreciprocity of the Kerr effect has been published in Optica. https://doi.org/10.1364/OPTICA.5.000279
Leonardo Del Bino won a best poster award at the “653. WE-Heraeus-Seminar: Optical Microcavities and Their Applications” for his poster on optical isolators and circulators based on the nonreciprocity of the Kerr effect in microresonators.
Jonathan Silver received the “Best Presentation Award” of NPL’s time and frequency symposium.
Jonathan Silver was awarded a postdoctoral research fellowship by the Royal Academy of Engineering for work on applications of spontaneous symmetry breaking between counterpropagating light in whispering gallery microresonators. Congratulations Jonathan!
Pascal Del’Haye received this year’s Young Scientist Award of the European Frequency and Time Forum. The award was presented during the plenary session of the EFTF/IFCS conference in Besancon “For outstanding contributions to the development of microresonator–based optical frequency combs”.
Leonardo Del Bino was rewarded with the Incubic/Milton Chang travel grant for his work on symmetry breaking of counterpropagating light in microresonators. The grant covers travel costs to this year’s CLEO conference in San Jose, CA USA. Congratulations Leonardo! http://www.osa.org/en-us/foundation/programs/incubic/
Pascal Del’Haye received a Horizons2020 Marie-Sklodowska-Curie Grant for research on nonlinear interaction of counter-propagating light.
That's all 71 posts, back to March 2017.
Recent publications
Full list- Spatial characterization of nonlinear optical states in microresonators via scattered light imagingAdv. Photon. Nexus 6, 016005 (Oct 2026)arXiv:2507.05450 (July 2025)
- Twin-photon generation in a silicon nitride microresonatorarXiv:2609.04171 (Sep 2026)
- Demonstration of a Single-Laser-Diode-Pumped Ti:Sapphire Astrocomb on the Southern African Large TelescopearXiv:2608.04733 (Aug 2026)
- Color Symmetry Breaking in a Nonlinear Optical MicroresonatorLaser Photonics Rev., e71644 (Aug 2026)arXiv:2601.00792 (Jan 2026)
That's all 89 publications. Full list by year
What we work on
Microcombs and solitons
How a single laser becomes many evenly spaced colours in a ring resonator, and what those combs are good for.
Quantum light on a chip
Photon pairs and nonclassical light from integrated microresonators.
Symmetry breaking and neuromorphic photonics
Light that spontaneously picks one of two states: optical switches, memories and logic gates, towards computing with light.
Nonlinear photonics
New colours and new light sources from nonlinear optics in microresonators: harmonic generation, Raman lasing and coupled resonators.
Integrated platforms and fabrication
Low-loss silicon nitride and aluminium nitride chips, made in our own cleanroom.
Two postdoc positions are open
We are looking for experimentalists with a background in nonlinear or quantum optics. Send a CV and a short note about what you want to work on.
- Microcombs and optical clocks
- Chip-based quantum light states
- Neuromorphic computing with light
- Nonlinear optics
- Microfabrication in our cleanroom
Microcomb simulator
Change the dispersion, detuning and pump power, and watch the comb form in your browser. Built by the group and free to use.
The group
We are physicists and engineers from many countries, working together on experiments, simulations and chip fabrication. PhD students, master's students and visitors join us through the Max Planck School of Photonics, FAU Erlangen-Nürnberg and international programmes.
