Our research aims at visualizing biological samples to elucidate the functions of biomolecules by utilizing the leading-edge pulsed laser technology and photonics technology. Specifically, we have developed stimulated Raman scattering (SRS) microscopy, which allows for detecting biomolecules by SRS, which is one of the interactions between light and molecules. We are pushing its performance and working on its biomedical applications. The research topics include measurement principles, laser sources, control systems, optics systems, and data analysis methods. Daily research is usually a steady process of experiments, but the moment when the laser oscillates or you see the image of a biological sample is a lot of fun. Let’s use electronics as a tool to explore the interdisciplinary field of physics, chemistry, biology, and medicine!

SRS microscopy detects molecular vibrations at a specific frequency, which is determined by the difference between the optical frequencies of the two-color laser pulses. For this reason, it was difficult to distinguish multiple types of biomolecules with a conventional SRS microscope. We have developed a laser light source [1] that can switch wavelengths at high speed, and realized a hyperspectral SRS microscope that can image multiple types of biomolecules by acquiring SRS images at various molecular vibrational frequencies in seconds to tens of seconds [2].
[1] Y. Ozeki et al., Opt. Lett. 37, 431 (2012).
[2] Y. Ozeki et al., Nature Photon. 6, 845 (2012).

We have developed an ultrafast wavelength-switched laser pulse source to realize SRS measurements of large numbers of cells and demonstrated multicolor SRS imaging of cells in a high-speed flow [1]. This technology makes it possible to image biomolecules contained in each of 10,000 or more cells to realize the imaging of nutrients contained in microalgal cells, and label-free imaging of blood cells and cancer cells.
[1] Y. Suzuki et al., Proc. Natl. Acad. Sci. U.S.A. 116, 15842 (2019).

We are utilizing quantum optics to realize ultra-sensitve SRS microscopy. The signal-to-noise ratio of current SRS microscopy is limited by the quantum fluctuation of light (vacuum fluctuation). In order to reduce this fluctuation, we are utilizing quantum-mechanical light called squeezed light in SRS microscope to increase the signal-to-noise ratio of the SRS signal [1].
[1] Y. Ozeki et al., J. Opt. Soc. Am. B 37, 3288 (2020).