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Advancing ultrafast magneto-optical imaging using ultra-low noise qCMOS® technology
Published July 16, 2025
Ultrafast pump-probe experiments enable precise studies of magnetization dynamics via magneto-optical effects. This allows researchers to monitor the behavior of magnetic materials as they evolve over ultra-short time intervals, offering insights into fundamental physics and facilitating the development of new technologies. Here we highlight single-shot all-optical switching experiments using a qCMOS camera, which excels in detecting weak signals from single 50 fs pulses. Its low noise and high quantum efficiency make it ideal for capturing ultrafast magnetic changes with high spatial resolution.
Single-shot all-optical switching experiments
Over the past twenty years, laser pulse excitation has become one of the most adaptable tools in the study of magnetization dynamics. This area of research has uncovered new and intricate mechanisms for the optical control of magnetization. It has garnered significant attention for its scientific intrigue and its promising commercial applications, such as in magnetoresistive random access memory (MRAM), spin-logic devices, and race-track memory. In all-optical pump-probe experiments, changes in magnetization are measured through magneto-optical effects, specifically the rotation of light polarization by an angle proportional to the magnetization. The use of ultrashort pulsed light sources allows for sub-picosecond time resolution, enabling detailed investigation of the temporal evolution of magnetization following impulsive excitation. However, detecting the weak magneto-optical signal from a single 50 fs pulse during irreversible all-optical switching remains a challenge [1].
The benefits of ORCA®-Quest for single-shot all-optical pump-probe experiments
The main function of a scientific camera in magnetization dynamics studies is to detect magneto-optical signals with (sub-)micron spatial resolution. Key requirements for such a camera include low noise and high quantum efficiency at the target wavelength, as the signal is delivered by a single ~50 fs laser pulse. Moreover, the polarization rotation in the experiments can be as small as a few millidegrees. As a single laser pulse contains a limited number of photons, a specialized camera like the ORCA-Quest, which features low read-out noise and short exposure time, is ideal. Additional essential features for the camera include robust synchronization with the laser and other electronics in the setup, high dynamic range, pixel bit depth, and seamless integration with adaptable software.
Like many people in the research field of ultrafast magneto-optical imaging, we used CCD cameras. However, the qCMOS sensor looks like a game changer with its unbeatable low read-out noise. Moreover, we measure optical second harmonic images in other experiments on laser-induced dynamics, which require a long exposure time, up to a few minutes. Again, the ORCA-Quest provides quality images due to high quantum efficiency, large number of pixels and onboard binning options.
Example of optically switched magnetic areas: bright and dark colors represent opposite orientation of the out-of-plane component of magnetization. In both images, the centers of pumped areas are fully demagnetized and form a multi-domain patterns. The outer edge is switched and can also be toggled back and forth with a second laser pulse. This is visible in the areas of overlapping laser pulses, giving rise to bright and dark altering regions.
Scan mode: Ultraquiet scan mode; Readout mode: Area; Binning 4×4, Trigger: Global reset. Exposure time: (left) 33.94 μs = single 100 fs probe pulse, (right) 100 ms = 100 probe pulses.
Future prospects for research
In the future, the implemented technique will be extended to antiferromagnetic materials with zero net magnetization. The visualization of the domains in such a class of materials is challenging and requires advance linear and non-linear optical techniques [2, 3].
In summary, the ORCA-Quest camera enhances single-shot magneto-optical imaging by reliably detecting weak signals from ultrafast laser pulses. Its performance supports both single-shot switching studies and long-exposure imaging. This approach will be extended to antiferromagnetic materials in future research, necessitating the use of advanced optical techniques for domain visualization. This will contribute to the further development of our comprehension of magnetization control and its potential applications in MRAM, spintronic devices, and other fields.
Researcher profiles
Dr. Nikolai Khokhlov
Postdoc at Ultrafast Spectroscopy of Correlated Materials group, Radboud University, The Netherlands
Dr Nikolai Khokhlov is a postdoc at Ultrafast Spectroscopy of Correlated Materials group, Radboud University, The Netherlands. He received his Ph.D. in Physics from M.V. Lomonosov Moscow State University, and completed postdoctoral training at Russian Quantum Center (Moscow, Russia). He then joined the Ferroics Physics Lab of Ioffe Institute (St. Petersburg, Russia) as assistant professor prior to his current position at Radboud University. Dr Khokhlov’s research centers around laser-induced ultrafast dynamics and all-optical switching of ferri- and antiferro-magnets implementing ultrafast magneto-optical microscopy technique.
Paul van Kuppevelt, MSc
Ph.D. candidate at the Ultrafast Spectroscopy of Correlated Materials group, Radboud University, The Netherlands
Currently, Paul van Kuppevelt performs his Ph.D. in physics at the Radboud University in Nijmegen. Before starting his research, he studyied physics at the Eindhoven University of Technology where he obtained his Bachelor’s and Master’s degree. During both his Bachelor’s and Master’s thesis, he focussed on the interaction of light with matter. At first by comparing models and experiments of the plasmon resonance in gold nanoparticles and later by performing logic operations with circular polarized light pulses in magnetic multilayer nanofilms. Now he continues in this field for his Ph.D. He is searching for ways in which to change and manipulate the magnetic state of ferri- and antiferromagnets to control the ultrafast dynamics inside these materials, which can be leveraged for applications like magnetic computing and data storage.
Wiebe Leenders, BSc
Master student at Ultrafast Spectroscopy of Correlated Materials group, Radboud University, The Netherlands
A Master’s student in physics, Wiebe Leenders is currently conducting research internship with the Ultrafast Spectroscopy of Correlated Materials group at Radboud University. Building on his previous research experience in material science and photovoltaics, he now focuses on optically excited ultrafast spin dynamics. Upon completion of internship, he will continue exploring magnetic materials and their potential for neuromorphic computation paradigms.
References
[1] Hashimoto, Yusuke, et al. "Ultrafast time-resolved magneto-optical imaging of all-optical switching in GdFeCo with femtosecond time-resolution and a μm spatial-resolution." Review of Scientific Instruments 85, 6 (2014).
[2] Hayashida, T., et al. "Observation of antiferromagnetic domains in Cr2O3 using nonreciprocal optical effects." Physical Review Research 4(4), 043063 (2022).
[3] Fiebig, Manfred, et al. "Second harmonic generation and magnetic-dipole-electric-dipole interference in antiferromagnetic Cr2O3." Physical Review Letters 73(15), 2127 (1994)
Related product
The ORCA-Quest 2 is a new qCMOS camera, the successor to the ORCA-Quest with further advances such as faster readout speeds in extremely low-noise scan mode and increased sensitivity in the ultraviolet region.
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