Development of nonlinear optical microscopy and spectroscopy for micro world study

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MIZUTANI Laboratory
Professor：MIZUTANI Goro

E-mail：
［Research areas］
Surface and Interface Science
［Keywords］
Surface nonlinear optical spectroscopy and microscopy

Skills and background we are looking for in prospective students　

Ability to think of physical phenomena in general, knowledge of electromagnetic theory, and laser technique.

What you can expect to learn in this laboratory

Students will learn optical characterization technology of materials, including laser operating skills. They will learn how to detect a weak optical signal from a sample excited by laser light and how to get its nonlinear optical susceptibility. They will learn how to use electronic equipment for signal processing. They have a chance to learn ultra-high vacuum technique for for surface science. They will experience presentation of their results in domestic and international conferences. They are encouraged to use English to communicate with international members. Each student will be appointed as a chairman in group meetings for practicing leadership.

【Job category of graduates】
Electronics manufacturer, mechanical manufacturer, chemical manufacturer, city office technical position, national university corporate faculty member.

Research outline

We are developing new microscopes and spectrometers using optical second harmonic generation (SHG) and optical sum frequency generation (SFG) for studying materials. In SHG and SFG two laser photons merge into a single photon with sum photon energy in a material with structures lacking inversion symmetry. We aim to observe and elucidate unique phenomena at the surface and interface of solids and biological systems. We are also interested in the various origins of nonlinear optical effect. We are interested in several research topics as below.

1. Development and application of second harmonic and sum frequency generation microscopes

We develop SFG and SHG microscopes more and more and try to demonstrate the power of these microscopes by applying them to observation of various interesting systems. As an example we show a photo of our confocal sum frequency generation microscope on the right hand side. The system to be observed are a catalyst surface, a semiconductor surface, a living organism, etc. It is our dream if we can find new physics from these systems.

2. Elucidation of surface and interface electronic states by second harmonic spectroscopy.

By using second harmonic spectroscopy, we can understand how the surface electronic state level change in an important surface and interface phenomenon. Electronic state of catalytic TiO₂ interface, surface adsorbates, semiconductor interface and liquid crystal substrate interface are investigated and compared to the first principle calculation.

3. Observation of new properties of surface only.

The molecules, membranes and nanostructures adsorbed on the surface show quite different properties when they are compared with the bulk of the same materials. For example, we are exploring the origin of differences of metallic nanowires and developing new functional substances that utilize this property.

4. Surface processing by using femto-second laser.

By using ultrashort pulse laser (1/10¹³ s), surface processing is not only expected to contribute to the production of state-of-the-art devices but also in understanding of microscopic mechanism.

Key publications

1. Y. Zhao, Y. Li, K. T. T. Hien, G. Mizutani, and H. N. Rutt, “Observation of spider silk by femtosecond pulse laser second harmonic generation microscopy”, Surface and Interface Analysis 51, 56-60 (2019).
2. M. E. Haque, D. Kobayashi, Y. Tomatsu, K. T. T. Hien, G. Mizutani, M. M. Rahman, and H. N. Rutt, “Optical second harmonic generation analysis of the atomically stepped Au/TiO2(320) interface”, AIP Advances 7, 125011 (2017).
3. K.T.T. Hien, M.A. Sattar, Y. Miyauchi, G. Mizutani, and H.N. Rutt, “Sum frequency generation spectroscopy study of hydrogenated stepped Si(111) surfaces made by molecular hydrogen exposure”, Surface Science 663, 11-15 (2017).

Equipment

Nd:YAG laser
Optical parametric generator
Regenerative Amplified Femtosecond Laser system
SHG and SFG spectrometers
Confocal sum frequency generation microscope
Ultrahigh vacuum sum frequency generation microscope