Seiji Ogino

Midinfrared free electron laser power delivery through a chalcogenide glass fiber

This article reports on the results of free electron laser (FEL) power transmission measurements through chalcogenide fibers. The FEL power transmission was tested by two types of chalcogenaide NSEG fibers, a normal fiber and a tapered fiber, made by varying the drawing speed from 2 to 17 cm/min. As a result, the tapered NSEG fiber is able to transmit 5–7 μm FEL power with a 10 MW/micropulse without surface damage. Tapered NSEG fibers are useful, therefore, for power transmission to narrow spaces such as the slide glass between the stage and the objective lens in a microscope.

The surface modification of tooth dentine with a Free Electron Laser (FEL)

Abstract Free Electron Laser (FEL) with the wide wavelength tunability has been developed and used for various applications. The FEL gives high efficiency for the photo-induced ablation when the laser is tuned to an absorption maximum of the target. The FEL was tuned to 9.4 μm, which is an absorption maximum of phosphoric acid ion, a known major component of dentine. The FEL pulse length was several ps. The average output power was varied from 5 to 20 mW by filters. The change of irradiated dentine surface was analyzed by mass spectroscopy and Energy Dispersive X-ray (EDX) spectroscopy. Positive ions which correspond to Na + , CO 3 + and many phosphoric acid ions were measured. It was found that atomic ratio of P/Ca had reduced from 0.65–0.60. The atomic ratio of P/Ca, however had not changed with irradiation by Er:YAG laser (2.9 μm), or CO 2 laser (10.6 μm). These results indicate the selective ablation of phosphoric acid ion by the 9.4 mm FEL irradiation.

Free-electron-laser (FEL)-induced desorption of ions from tooth dentine

Free electron laser (FEL) with the wide wavelength tunability has been developed and used for various applications. The FEL gives high efficiency for the photo- induced ablation when the laser is tuned to an absorption maximum of the target. This study investigates the FEL induced desorption of ions from tooth dentine to find new possibility for laser dentistry. The FEL was tuned to 9.4 (Mu) m, which is an absorption maximum of phosphoric acid ion known as major component of dentine. The FEL pulse length was several ps. The output average power was varied from 5 to 20mW by filters. A time-of-flight mass spectroscopy systems were developed for the purpose of analyzing the desorbed ions of varying masses. After the 9.4 micrometers FEL irradiation, the dentine surface was ablated, and visible light emission was observed. As a result, positive ions which correspond to Na+ and many phosphoric acid ions were measured. The positive ions, however were not observed when the FEL was not tuned to the absorption peak of the target. Therefore, this wavelength dependence points to resonant multiphoton vibrational excitation of molecules by the 9.4 micrometers FEL irradiation.

Effect of free electron laser (FEL) irradiation on tooth dentine

Free electron laser (FEL) gives high efficiency for the photo-induced effects when the laser is tuned to the absorption maximum of target materials. The effect on dentine was investigated using the FEL tuned to 9.4 micrometers , which is an absorption maximum of phosphoric acid in infrared region. As a result, irradiated dentine surface which was amorphous had changed to the recrystalized structure by the spectroscopic analysis of IR absorption and x-ray diffraction. Furthermore, the atomic ratio of P/Ca had reduced from 0.65 to 0.60. These results indicated that 9.4micrometers -FEL irradiation caused the selective ablation of phosphoric acid ion and the reconstruction of disordered atoms.

Free electron laser (FEL) annealing of diamond

Abstract Free Electron Laser (FEL) with wide wavelength tunability has been developed and used for various applications. We report the structural-changes in P-ion-implanted diamond when we can achieve resonant excitation of the vibrations of specific bonds in the lattice of target (P–C) by using FEL. The change of property was analyzed by SIMS and Raman spectroscopy. After 5.8 μm-FEL irradiation, we observed the crystallization of amorphous structure which was induced by P-ion-implantation. These results indicated the FEL annealing of diamond at room temperature.

Free electron laser synthesis of microfiber silicon and its visible light emission

Abstract Novel Si microstructures were synthesized by irradiation of infrared free electron lasers into a-Si:H films. The synthesized microstructures showed micrometer-sized complicated fiber structures called Si microfibers. The Raman spectrum showed the presence of Si nanometer-sized structures (Si nanostructures). The IR absorption spectrum showed that a part of the Si atoms bonds the hydrogen atoms. Pronounced red photoluminescence from the Si microfiber was observed at room temperature. The synthesis of Si microfibers containing Si nanostructures is discussed by taking the novel pulse structure of the free electron lasers into account.

Development of a micro FEL irradiation system

Abstract A microscopic Free Electron Laser (FEL) irradiation system has been developed for bio-medical applications. This system has two major functions; irradiation and observation. This irradiation system cannot only focus the FEL from infrared to ultraviolet in wavelength but can also adjust the area, time and intensity of FEL irradiation. Furthermore, experimental cells are incubated and observed in detail during and after FEL irradiation with an integrated microscope.

Delivering dye into cultured cells using infrared free-electron laser

Free electron lasers (FELs) can be used to molecular operation such as the delivery of a number of molecules into cells. Cultured NIH3T3 cells are exposed to high-intensity short pulse FEL. The FEL is tuned to an absorption maximum wavelength, 6.1 micrometers , which was measured by microscopic FTIR. A fluorescence dye in the cell suspension is more absorbed into the cell with the FEL exposure due to the FEL- induced mechanical stress to the cell membrane. A quantitative fluorescence microscopy is used to determine the efficiency of delivery. The result showed that the fluorescence intensity of sample cells were higher than that of control cells, and there was significant difference between the control and the sample group. Blebbing and the colony formation of the cells were observed for cells with mechanical stress.

The Surface Modification with FEL Ablation

Free Electron Laser (FEL) having the broad tunability and the unique short pulse structure has been developed and used for various applications. Our FEL irradiation experiments show high efficiency for the photo-induced ablation when the laser is tuned to absorption maximum of the target. Using the FEL tuned to phosphoric acid ion (9.4um) which is an absorption maximum in infrared region on dentine, we in(平 成10年11月9日 受 理,Received December 9th 1998) 64 日 レ 医誌(JJSLSM)第20巻 第1号(1999) vestigate the irradiation effect on dentine. The change of property was analyzed by mass spectoscopy and Energy Dispersive X-ray (EDX) spectroscopy. As a result, the atomic ratio of P/Ca had reduced from 0.65 to 0.60. However it had not changed with Er : YAG laser (2.9 um) or CO2 laser (10.6 um). Furthermore it was observed that irradiated dentine surface which was amorphous changed to the recrystalized structure. These results indicate that 9.4 um-FEL irradiation caused selective ablation of phosphoric acid ion and annealing.

Molecular operation on elastic fibers and cholesterol ester by a free-electron laser

A method has been found to selectively ablate cholesterol esters accumulated in an arteriosclerotic region of a rabbit artery without damaging the blood vessel using a free-electron laser (FEL). A FEL is a pulsed laser source that generates a beam by amplifying the coherent radiation emitted by an electron beam that is traveling through a periodically alternating magnetic field at a relativistic velocity. The characteristics of the FEL include a broadly tunable wavelength and ultra-short pulse width. We have found that FEL irradiation of a rabbit arterial wall for 1 min with a power of 1.5 mW can ablate cholesterol esters without damaging the elastic fibers of the arterial wall. The FEL was tuned to 5.75 micrometer, which is a wavelength that is absorbed by cholesterol ester. This method may be used as a non-invasive surgical procedure for the treatment of arteriosclerotic arteries.