OIST Optics Seminars 2025
Title: Ultrasensitive ultrasound sensing with integrated optical microresonators
Speaker: Dr Beibei Li, Professor, Institute of Physics, Chinese Academy of Sciences, China
Abstract:
Ultrasound sensing is widely adopted in various applications, including medical imaging, non-destructive testing, underwater acoustics, and industrial process monitoring. Conventional ultrasound transducers, typically based on piezoelectric materials, have been widely used in these applications. However, these transducers face challenges in terms of miniaturization, integration, and sensitivities, which restrict their applications in scenarios that require compactness and high resolutions. Recently, ultrasound sensors based on optical microcavities have been developed, which provide the advantages of high sensitivities, broad bandwidth, low power consumption, and chip-integration capabilities. However, it is challenging to achieve high sensitivity using integrated optical microresonators.
In this work, we demonstrate a novel integrated, high-sensitivity optomechanical ultrasound sensor (Figs. 1a-1c) consisting of a suspended SiO2 membrane and an embedded Si3N4 microring resonator. Due to the mechanical resonance enhanced response of the SiO2 membrane and the optical resonance enhanced readout sensitivity of the high-Q Si3N4 microring resonator, this sensor achieved a NEP of 9.6 nPa Hz-1/2 in the water environment (Fig. 1d). We further apply the sensor for ultrasound imaging in water, achieving a spatial resolution of 1.34 mm (Fig. 1e). This fully integrated, high-sensitivity ultrasound sensor opens new possibilities for a range of applications such as underwater ultrasound imaging, photoacoustic imaging, etc.
Upcoming Seminars
Title: Multipliers of orbital angular momentum of light
Speaker: Dr Georgiy Tkachenko, University of Bordeaux, France
Abstract:
I will present recent works on passive optical elements that enable the multiplication or division of orbital angular momentum in vortex beams. While primarily designed for advanced optical telecommunications, these elements also exhibit intriguing optomechanical properties.
Thursday, 10 April, 10:30-11:30am, on zoom
Title: Plasmonic Optical Tweezers: From Nanoparticles Trapping to Biomolecules Manipulation
Speaker: Dr Domna Kotsifaki, Assistant Professor of Physics, Duke Kunshan University, China
Abstract:
Plasmonic optical tweezers (POT) have emerged as a groundbreaking technology for the precise manipulation of nanoscale objects, overcoming the diffraction limits of conventional optical trapping [1-5]. This talk will provide an overview of the physics behind POT, focusing on using plasmonic nanostructures with unique properties, such as Fano-resonant metamaterials, to achieve stable trapping of nanoparticles as small as 10 nm. I will present experimental demonstrations of single nanoparticle trapping, as well as the dynamic manipulation of multiple nanoparticles in lab-on-chip environments. Furthermore, I will discuss the application of POT in biomolecular studies, including the trapping and discrimination of enzymes and dielectric particles using advanced statistical tools such as probability density functions and violin plots. Finally, I will highlight recent advancements in the optothermal trapping of lipid vesicles, demonstrating how thermal-gradient-induced forces can be utilized for efficient drug delivery and biosensing. By combining theoretical insights with experimental results, this talk will highlight the transformative potential of plasmonic optical tweezers in nanoscience, biophysics, and nanomedicine.
[1] D.G.Kotsifaki, V.G. Truong, S. Nic Chormaic, Fano-resonant, asymmetric, metamaterial-assisted tweezers for single nanoparticle trapping, Nano Letters 20(5), 3388-3395 (2020).
[2] D.G. Kotsifaki, V.G. Truong, S. Nic Chormaic, Dynamic multiple nanoparticle trapping using metamaterial plasmonic tweezers, Applied Physics Letters 118(2), 021107 (2021).
[3] T.D. Bouloumis, D.G. Kotsifaki, S. Nic Chormaic, Enabling self-induced back-action trapping of gold nanoparticles in metamaterials plasmonic tweezers, Nano Letters 23(11), 4723-4731 (2023).
[4] D.G. Kotsifaki, V.G. Truong, M. Dindo, P. Laurino, S. Nic Chormaic, Hybrid metamaterial optical tweezers for dielectric particles and biomolecules discrimination, arXiv preprint arXiv:2402.12878 (2024).
[5] Z. Jiang, Y. Sun, Y. Gao, L. Xu, D.G. Kotsifaki, Fast lipid vesicles and dielectric particles migration using thermal-gradient induces forces, Journal of Optics 26(9), 095301(2024).
Friday, 11 April 2025, 13:00-14:00, C209
Title: Micro- and Nanomotors Driven by Optical Forces and Torques
Speaker: Dr Mikael Käll, Professor, Department of Physics, Chalmers University of Technology, Sweden
Abstract:
Almost all engines and motors that we utilize in our macroscopic world are driven by light energy, in the form of fuels derived from photosynthesis or electricity generated by photovoltaics. In the micro and nanoworld, however, it is also possible to utilize light momentum to generate mechanical movement. In this talk, I will discuss some of our recent works in this field with a focus on two different systems. In the first case, we investigate plasmonic rotary nanomotors, which can rotate at kHz frequencies in water due to spin angular momentum transfer [1]. Surprisingly, we recently found that these tiny objects can optically self-organize into regular arrays and synchronize their rotational movement in a manner that is essentially captured by the famous Kuramoto model of synchronization behaviors [2]. The second system consists of micromotors that utilize photon recoil in optical metasurfaces to generate translation and rotation. We constructed microscopic "metavehicles" able to navigate across a surface in water under plane-wave illumination, while being steered through the incident polarization [3], as well as “metaspinners” [4] and “metarotors” [5] that rotate because they generate orbital angular momentum from unstructured incident light. Although these works are mostly motivated by curiosity, there might also be an application potential. For example, rotary nanomotors can be used as ultrasensitive rheological sensors [1]; metavehicles can be used as transporters of microscopic cargo [3], and metarotors can be used to rotate hundreds of passive microparticles in solution [5]. It is even possible to transform metaspinners into tiny cogwheels for optically driven micromachinery [6].
[1] L. Shao et al, Adv. Funct. Mat. (2018), https://doi.org/10.1002/adfm.201706272
[2] X. Cui et al, Science Advances (2024), DOI: 10.1126/sciadv.adn3485
[3] Andrén et al, Nature Nanotechnology (2021). https://doi.org/10.1038/s41565-021-00941-0
[4] Engay et al., Light: Science & Applications (2025). https://doi.org/10.1038/s41377-024-01720-x
[5] Shanei et al, Nano Letters (2025). https://pubs.acs.org/doi/10.1021/acs.nanolett.4c06410
[6] Wang et al., arXiv preprint (2025). arXiv:2409.17284
Bio:
Mikael Käll is an experimental physicist focusing on fundamental and applied nanooptics and biophotonics. His current research projects deal with the physics and applications of optical metasurfaces and optical forces. He has previously worked with topics like surface-enhanced Raman scattering, plasmonic biosensors, optical antennas, bioimaging, and strongly correlated electron systems. He has co-authored more than 200 journal papers that have been cited more than 30000 times to date.
Past Seminars
Title: Nonlinear Photonics in High-Q Microcavities: From All-Optical Switches to Microresonator Frequency Combs
Speaker: Dr Takasumi Tanabe, Professor, Electronics and Electrical Engineering, Keio University, Japan
Abstract:
High-Q micro and nanocavities, such as photonic crystal nanocavities and high-Q whispering gallery mode (WGM) microcavities, are attractive for applications that require strong interaction between light and matter, as the electric field density scales with Q/V, where V is the mode volume of the cavity. I will introduce all-optical switches in photonic crystals and high-Q WGM resonators, mode-locking in coupled microresonators, and optical frequency combs in microresonators.
[1] K. Nozaki, TT, et al. Nat. Photon. 4, 477-483 (2010).
[2] S. Fujii, et al. TT, "All-precision-machining fabrication of ultrahigh-Q crystalline optical microresonators,” Optica 7, 694 (2020).
[3] S. Fujii, et al. TT, "Mechanically actuated Kerr soliton microcombs," Laser Photon. Rev. 2024, 2301329 (2024).
[4] R. Imamura, et al. TT, "Exceptional point proximity-driven mode-locking in coupled microresonators," Opt. Express 32, 22280 (2024).
Title: Principles and applications of optical and acoustic trapping combined with Raman spectroscopy
Speaker: Dr Silvie Bernatova, CNR Italy
Abstract:
Optical and acoustic trapping is a method that uses optical or ultrasonic sound waves to trap and manipulate particles in air or a liquid. In this seminar, my aim is to introduce the basic principles of optical and acoustic trapping in combination with Raman spectroscopy. I will present a pair of portable setups that facilitate the trapping and manipulation of solid and liquid samples in water/air. The potential applications of both Raman tweezers will be demonstrated with examples that can be used in the detection of environmental pollutants.
A single atom coupled to an optical nanofiber cavity holds significant promise for quantum computing based on nanofiber cavity-QED. However, scaling this system is crucial for its practical implementation. In this talk, I will present our efforts to scale up the system by interfacing multiple individually addressable atoms with an optical nanofiber cavity. The techniques we are using, along with the challenges involved in achieving this goal, will be discussed.
Monday 3rd February 2025: 16:00-17:30, C209
Title: Imaging in 3D and other fun things to do through multimode fibres
Speaker: Dr Peter Mekhail, University of Glasgow, Scottland
Abstract:
We demonstrated live point-scanning reflection imaging through a hair-thin multimode fibre by using high-speed spatial light modulation. We have used this technique in 3D imaging with time-of-flight measurements from a Q-switched pulsed laser source. We have also explored live imaging with a hand-held version of the endoscope, using a calibration library to guide the process where the selection of the calibration positions were based on speckle correlations from fibres bent into various configurations. Additionally, we investigated the use of auto-encoding neural networks to improve image reconstruction as the fibre undergoes bending, for robust, real-time imaging in flexible settings. Finally, we extended the capabilities of multimode fibres by demonstrating sound recording through the fibre, using phase measurements obtained via high-speed light field reconstruction. This work underscores the versatility and potential of multimode fibres in advanced imaging and sensing applications.
Related papers:
Time-of-flight 3D imaging through multimode optical fibers
Single multimode fibre for in vivo light-field-encoded endoscopic imaging
Seeing through chaos in multimode fibres
Robust real-time imaging through flexible multimode fibers