Message

　We are studying on subjects utilizing lasers in a wide range of material science fields.  Setting ourselves free from the conventional concept of the material science, our research themes are chosen in order to make the best use of this new tool, the laser.

   We know that we know a little.  Therefore, we can challenge something unknown.  We welcome people who feels sympathy for this.

Research projects

Development of nano-manipulation technique of atomic beam

     Generation of a monochromatic atomic beam

     Development of a tunable, doughnut laser beam (future planning)

     Atom focusing by the laser beam (future planning)

Development of isotope separation by optically selective excitation of atoms

     Improvement of the effect of light induced drift

     Application for isotope separation of Alkali metals

Synthesis of advanced materials by ultra-short optical pulses

     Synthesis of thin films of hard materials such as boron nitride

     Synthesis of thin films of photo-catalysts such as titanium oxide

     Development of novel ablation technique of femto-second laser pulses

Development of cylindrical vector laser beam

     Generation of radially polarized beam using a novel optical element

     Application of axially symmetrical, polarized laser beam for material science (future planning)

Wavelength control

  The laser wavelength is inherently determined by the laser material used.  Since its spectral width is about one hundred-thousandth of the wavelength, the laser light is very monochromatic compared to the light from conventional light sources.  When decreasing further the spectral width by using external wavelength standard, we can selectively excite specific atoms.  In this case, atomic motion can be accurately controlled by the use of the light.  In our lab, generation of monochromatic atomic beam and isotope separation are under study using semiconductor lasers. detail

Spectral width control

The spectral width of the laser is determined by the laser material, structure and so on.  This means that it is not easy to obtain a laser light with desirable spectral width.  In our lab, we are controlling the spectral width using a frequency modulation technique.  By tuning laser wavelength to the absorption, it is possible to efficiently excite the atoms.  In our lab, we are applying this technique to the so-called laser cooling and making a monochromatic atomic beam.  Our goal is to realize a atomic beam focusing to nanometer regime using an improved atom lens and establish a basal technology for nano-fabrication using atoms and lasers.  detail

Pulse width control

Lasers are operated in either continuous or pulsed.  In the case of pulsed operation, most of them are operated by a Q-switching technique producing nano-second (~10^-9 sec) pulses.  A mode-locking technique can decrease further the pulse width to femto-second (~10^-15 sec) regime.  Since this time domain is shorter than the electron-lattice relaxation time, these ultra-short pulses are used for analyzing ultra-fast phenomena.   When these pulses are irradiated on material, high temperature upto several thousands degrees is easily realized because of absorption of the instantly intense laser light.  This causes succeeding evaporation of the material surface.  The fraction of the evaporated materials can be used for thin film deposition.  In our, lab, thin films of titanium oxide known as a efficient photo-catalyst and boron nitride known as high-temperature, wide bandgap semiconductor are synthesized.  Our goal is to establish a novel material  producing technique making the best use of the femto-second laser pulses.  detail

Polarization control

Linear and circular polarizations are known as a light polarization. While its spatial distribution is homogeneous in general, recent researches reveal the possibility of generating a radially and azimuthally polarized laser beams and their focusing characteristics of the radially polarized laser beam is remarkably unique.  In our lab, we are fabricating the radially polarized laser for the application to optical trapping of opaque micro- and nano-particles, of which trapping has been impossible.  We found some interesting features by calculation for beams with different transverse modes.  detail

List of instruments in our laboratory

Contact

Send your message to Dr. Nakamura.