When light, such as a laser, is irradiated onto matter, the dynamics of atoms and electrons within the material are driven. We have been studying these driven atomic and electronic dynamics using microscopic simulations based on quantum mechanics. Furthermore, through these simulation approaches, we are also studying the microscopic physical processes underlying light-induced phenomena.

In conventional materials science calculations, first-principles simulations based on density functional theory have been widely used to study the equilibrium properties of matter. However, such equilibrium approaches are not well suited to capturing the dynamics driven by light within materials. Our research method employs time-dependent density functional theory, which can handle material dynamics, thereby going beyond equilibrium descriptions and enabling precise analysis of nonequilibrium phenomena, nonlinear effects, and ultrafast processes driven by light.

• * First-principles calculations for optical science
• * Real-time simulations of nonequilibrium dynamics of electrons and atoms
• * Clarifying microscopic mechanisms behind macroscopic phenomena induced by light

We are developing theoretical and computational methods to accurately describe the nonlinear and nonequilibrium dynamics of atoms and electrons driven by light. We are also conducting research aimed at creating new science and technology based on light-driven phenomena. We hope that our research will contribute to the social implementation of new scientific and technological advances.

• 　Using laser fabrication, we are developing techniques to enhance material surface properties and functionality. For example, to create a functional interface, we aim to clarify, by way of simulation and experimentation, the phenomenon that occurs when the surface of a material is irradiated using a laser beam.
• 　We expect that the results of our research will be widely applicable, including biomedical devices.
• ■　Creation of biocompatible surfaces
• 　Materials used for artificial organs, vessels, and other bio-implants require excellent tissue and cell biocompatibility. Therefore, we are exploring the creation of biocompatible surfaces using a new laser irradiation process in this study.
• 　We have succeeded in imparting a biologically active function to titanium-based materials by applying the laser irradiation technique. When such a material that has a biologically active function is inserted in a living body, hydroxyapatite (the principal constituent of bones and teeth) precipitates on the surface. Using the laser irradiation technique, we can manufacture bone-adherent implants, and we envisage their application to artificial joints or dental implants.
• 　This research aims to discover such breakthrough solutions for biomedical applications using the laser irradiation technique.

• Nakagawa group has dedicated to pursue scientific principles for molecular control of interface function occurring at polymer/other material interfaces and to put them into practice in nanoimprint lithography promising as a next generation nanofabrication tool. We are developing advanced photo-functional materials such as sticking molecular layers for "fix by light", UV-curable resins and antisticking molecular layers for "preparation by light", fluorescent resist materials for "inspection by light", and hybrid optical materials "available to light" and new research tools such as mechanical measurement systems to evaluate release property of UV-curable resins.

Our research aims at creating new devices to control photon, electron, and magnetism.

When light, such as a laser, is irradiated onto matter, the dynamics of atoms and electrons within the material are driven. We have been studying these driven atomic and electronic dynamics using microscopic simulations based on quantum mechanics. Furthermore, through these simulation approaches, we are also studying the microscopic physical processes underlying light-induced phenomena.

In conventional materials science calculations, first-principles simulations based on density functional theory have been widely used to study the equilibrium properties of matter. However, such equilibrium approaches are not well suited to capturing the dynamics driven by light within materials. Our research method employs time-dependent density functional theory, which can handle material dynamics, thereby going beyond equilibrium descriptions and enabling precise analysis of nonequilibrium phenomena, nonlinear effects, and ultrafast processes driven by light.

• * First-principles calculations for optical science
• * Real-time simulations of nonequilibrium dynamics of electrons and atoms
• * Clarifying microscopic mechanisms behind macroscopic phenomena induced by light

We are developing theoretical and computational methods to accurately describe the nonlinear and nonequilibrium dynamics of atoms and electrons driven by light. We are also conducting research aimed at creating new science and technology based on light-driven phenomena. We hope that our research will contribute to the social implementation of new scientific and technological advances.

• 1. Development of Distributed Feedback (DFB) Laser Diodes (LD) widely used in optical communications systems realizing a highly information-based society. This LD increases the transmission capacity by 25,000 times per fiber which means the bit rate of 10Tb/s.
• 2. Nitride semiconductors famous for blue light emitting diodes.
• (a) Proposal of InGaAlN system considering device applications in 1989
• (b) Success in growth of single crystalline InGaN by metalorganic vapor phase epitaxy (MOVPE) in 1989
• (c) Prediction of band-gap energy (Eg) of InN much smaller than the values reported in 1980s and its 　 experimental confirmation in 2002
• (d) Observation of photoluminescence from InGaN in 1991
• (e) Prediction of phase separation in InGaAlN in 1997

DFB-LD: Fabrication of periodic structure with submicron scale, Epitaxial growth of semiconductor films on the substrate with fine structures, LD fabrication process, device evaluation, and device simulation

Nitride Semiconductors: MOVPE growth, N-polar growth, Evaluation of semiconductor materials, Fabrication of light-emitting devices, solar cells, and high-power transistors

• Recently, with a spread of high definition video streaming services and ubiquitous network, development of high-quality, ultra-realistic and low-power display systems has been demanded. We have been studying physical properties of liquid crystal materials, precise control technique of polarization, high performance liquid crystal display (LCD) devices and its application to the advanced display systems for the realization of new media such as electric paper display and digital signage display, and low-energy society. We established a polarization control technology which realizes a precise control of polarization with liquid crystal materials. By using this world-leading technology, we have been studying the control of the surface alignment of liquid crystal molecules and developed a wide-viewing angle and fast switching liquid crystal display, ultra-high definition field-sequential-color display (Fig. 1), ultra-low power reflective full-color display (Fig. 2) and large-size high-quality display system.
• We are also studying the ultra-realistic display systems such as a spatial 3D display and a multiple directional viewing display based on the precise light control technique as a next generation interactive communication technologies (Fig.3). We hope to conduct collaborative research with a willing company for a practical application of this technology in industry.

• This group is engaged in basic and applied researches of "hydrides" for practical use in hydrogen energy system. The main subject is the exploration of advanced hydrogen storage materials which support hydrogen energy technologies such as fuel cells. Currently, we synthesize a wide variety of novel hydrides composed of lightweight metals with specific nano-structures using advanced techniques for crystal and electronic structure analyses. In addition to the hydrogen storage, we develop the wide research fields related to hydrides, such as fast lithium ionic conductors.

Besides the contributions in industrial progress through the material development for future hydrogen energy system and next-generation secondary battery, we positively provide technical assistance to organizations and companies concerned about our findings.

• Our focus is on the development of solid-state-ionics materials to be used for a variety of energy conversion systems. To further improve the performance of fuel cells and lithium batteries, novel ionic conductors and mixed conductors with high ionic conductivity and chemical stability are highly demanded. We have been developing such the materials based on defect chemistry and thermodynamics of ceramics, and trying to apply those materials to actual energy conversion devices.

To date, a hydrogen production system utilizing oxygen permeable membranes and an all-solid-state battery have been prepared.