尾松 孝茂

We have discovered that a novel chiral structured surface relief (termed 'conch'-shaped surface relief) with a height of over 1 mu m can be formed in an azo-polymer film merely by employing circularly polarized optical vortex irradiation with a total angular momentum of j = +/- 2. The temporal evolution of the conch-shaped surface relief in the azo-polymer film was also observed. The results provide physical insight into how the angular momentum of light is transferred to a material through mass transport by cis-trans photo-isomerization. Such conch-shaped surface reliefs with chirality, in which functional chemical composites can be doped, enable new applications, such as planar chiral metamaterials, plasmonic holograms, and identification of chiral chemical composites.

We present the first handedness control of an optical vortex output from a vortex-pumped optical parametric oscillator. The handedness of the optical vortex was identical to that of the pump vortex beam. Over 2 mJ, 2- μm optical vortex with a topological charge of ± 1 was achieved. We found that the handedness of a fractional vortex with a half integer topological charge can also be selectively controlled. © 2013 Optical Society of America.

We demonstrate the direct generation of a first-order LG(01) Laguerre Gaussian (vortex) mode operating at the first-Stokes wavelength of a diode end-pumped, Nd: GdVO4 self-Raman laser. To the best of our knowledge, this is the first report of intracavity stimulated Raman scattering (SRS) being used as a method for frequency conversion of a vortex laser beam and it is effective in enabling the frequency-converted (Stokes) beam to have the same LG(01) mode as the fundamental beam. (C) 2013 Optical Society of America

A high-average-power, high-beam-quality picosecond laser is presented that is based on CW diode side-pumped Nd:YVO4 thin-slab amplifiers having a bounce geometry. More than 65 W of output power with a beam quality of M-2 approximate to 1.3 is obtained at an optical-optical efficiency of 46%. (C) 2013 Optical Society of America

We discovered that chiral nanoneedles fabricated by vortex laser ablation can be used to visualize the helicity of an optical vortex. The orbital angular momentum of light determines the chirality of the nanoneedles, since it is transferred from the optical vortex to the metal. Only the spin angular momentum of the optical vortex can reinforce the helical structure of the created chiral nanoneedles. We also found that optical vortices with the same total angular momentum (defined as the sum of the orbital and spin angular momenta) are degenerate, and they generate nanoneedles with the same chirality and spiral frequency. DOI: 10.1103/PhysRevLett.110.143603

A small forbidden gap matched to low-energy photons (meV) and a quasi-Dirac electron system are both definitive characteristics of bilayer graphene (GR) that has gained it considerable interest in realizing a broadly tunable sensor for application in the microwave region around gigahertz (GHz) and terahertz (THz) regimes. In this work, a systematic study is presented which explores the GHz/THz detection limit of both bilayer and single-layer graphene field-effect transistor (GR-FET) devices. Several major improvements to the wiring setup, insulation architecture, graphite source, and bolometric heating of the GR-FET sensor were made in order to extend microwave photoresponse past previous reports of 40 GHz and to further improve THz detection. © 2013 Mahjoub and Ochiai; licensee Springer.

We have rationally designed and synthesized a novel near-infrared (NIR) photoactivating probe, designated by iDOPE, in which an indocyanine green (ICG) fluorophore is covalently conjugated with a phospholipid moiety, 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), to incorporate into liposome bilayers. NIR irradiation showed that iDOPE retained the optical and fluorescence properties of ICG and demonstrated photoactivator characteristics: fluorescence emission at around 820 nm in a solvent, singlet oxygen production, and concentration-dependent heat generation. Additionally, iDOPE was incorporated into liposome bilayers and maintained stable liposomally formulated iDOPE (LP-iDOPE) over 1 week under physiological conditions. We also observed the tumor-specific biodistribution of LP-iDOPE of in vivo xenografts. These findings suggest that LP-iDOPE might be a promising tool for NIR optical imaging, photodynamic therapy, and photothermal therapy. (C) 2012 Elsevier Ltd. All rights reserved.

We generated tunable 2-mu m optical vortex pulses with a topological charge of 1 or 2 in the wavelength range 1.953-2.158 mu m by realizing anisotropic transfer of the topological charge from the pump beam to the signal output in a vortex-pumped half-symmetric optical parametric oscillator. A maximum vortex output energy of 2.1 mJ was obtained at a pump energy of 22.8 mJ, which corresponds to a slope efficiency of 15%. The topological charges of the signal and idler output were investigated using a shearing interferometric technique employing a low-spatial-frequency transmission grating. (C) 2012 Optical Society of America

The highest power neodymium-doped mixed vanadate laser oscillator is presented. Using a crystal of Nd:Gd0.6Y0.4VO4 in the bounce geometry, average output powers of 27.5 W in multimode and 23 W in TEM00 operation were achieved. The first nonlinear mirror mode-locked operation of a mixed vanadate laser is also presented, with 16.8 W output power-the highest power mode-locked mixed vanadate oscillator, to the best of our knowledge. Self-starting continuous-wave mode locking was observed at a repetition rate of 100 MHz, pulse duration of 12.7 ps and central wavelength of 1063.8 nm, in TEM00 mode.

We have directly measured thermal lensing in a continuous-wave Nd-doped GdVO4 self-Raman laser under diode pumping at 808 and 879 nm. Thermal lensing increased significantly when generating first-Stokes emission, this most likely originating from impurity absorption and/or excited-state absorption at high pump powers. Pumping at 879 nm significantly reduced thermal lens effects in the laser crystal compared with pumping at 808 nm.

The thermal lens induced in an a-cut BaWO4 crystal by stimulated Raman scattering is measured using lateral shearing interferometry. The strength of the lens is proportional to the Stokes output power. For light polarized parallel to the a-axis, and a Stokes mode radius of 120 mu m, the lens is negative and highly astigmatic: -0.8 D W-1 in the plane parallel to the a-axis and -7.7 D W-1 in the plane parallel to the c-axis. The implications of this thermal lens for Raman laser design are discussed. (C) 2012 Optical Society of America

The current trends in stimulated Brillouin scattering and optical phase conjugation are overviewed. This report is formed by the selected papers presented in the "Fifth International Workshop on stimulated Brillouin scattering and phase conjugation 2010" in Japan. The nonlinear properties of phase conjugation based on stimulated Brillouin scattering and photorefraction can compensate phase distortions in the high power laser systems, and they will also open up potentially novel laser technologies, e. g., phase stabilization, beam combination, pulse compression, ultrafast pulse shaping, and arbitrary waveform generation.

Dual-frequency MHz-repetition 1.5-mu m optical parametric generation is demonstrated from a tandem system pumped by a picosecond Nd:YVO4 bounce laser. An average power of 1.0 W is obtained over the range 1571-1630 nm, corresponding to an optical-optical conversion efficiency and slope efficiency of 16% and 23%, respectively. Terahertz-wave with a frequency of 3.2 THz is also generated from the system in combination with an organic nonlinear DAST crystal. (C) 2011 Optical Society of America

Nanosecond vortex pulses were generated using a stressed, large-mode-area, Yb-doped, fiber amplifier with an off-axis coupling technique for the first time. A pulse energy of 0.83 mJ (corresponding to a peak power of 59 kW) was achieved at a pump power of 25.7 W. The optical-optical efficiency was measured to be 31%. The millijoule nanosecond vortex pulses will be potentially applied to novel material processing, such as metal microneedle fabrication. (C)2011 Optical Society of America

The first demonstration of a mid-infrared optical parametric oscillator pumped by 1-mu m optical vortex pulses is presented. A 0.5-mJ 2-mu m fractional vortex pulse having half-integer topological charge is generated. Using this system, 0.24-mJ vortex pulses with a topological charge of 1 can be created. The topological charges of the mid-infrared vortex pulses are observed by an interferometric technique in combination with second-harmonic frequency conversion. (C) 2011 Optical Society of America

We investigated the properties of 4,4'-biphenyl dicarboxylic acid diethyl ester (PCE). The PCE underwent a 2-step reduction at -1.5 V and -2.2 V. The color of the PCE changed from colorless to yellow in the first step and consequently to red in the second reduction step. A PCE based EC cell using an NiO-modified electrode was also fabricated. The NiO electrode worked as a counter reaction material for PCE reduction. The PCE-NiO cell achieved multi-coloration ranging from colorless to yellow and red, and also achieved high coloration efficiency and long term switching stability.

Power scaling of a picosecond vortex laser based on a stressed Yb-doped fiber amplifier is analyzed. An output power of 25 W was obtained for 53 W of pumping, with a peak power of 37 kW. Frequency doubling of the vortex output was demonstrated using a nonlinear PPSLT crystal. A second-harmonic output power of up to 1.5 W was measured at a fundamental power of 11.2 W. (C) 2011 Optical Society of America

6.5-W, 1.3-A mu m passively Q-switched output was demonstrated from a side-pumped Nd-doped Gd(0.6)Y(0.4)VO(4) bounce laser in combination with a V:YAG saturable-absorber crystal. Experimental output powers of 6.5 W and 6 W were measured at a maximum pump level in multi- and TEM(00)-mode operations, corresponding to optical-to-optical efficiencies of 17.5% and 16.2%, respectively.

Microneedle fabrication on a metal surface based on laser ablation using twisted light with spin was demonstrated, for the first time. The resulting needle showed a height of at least 10 mu m above the target surface and a tip diameter of less than 0.3 mu m. We also demonstrated the fabrication of a two-dimensional 5 x 6 microneedle array. The needles were uniformly well shaped with an average length and tip diameter of about 10 and 0.5 mu m, respectively. (C) 2010 Optical Society of America

Laser ablation of Ta plates using nanosecond optical vortex pulses was carried out, for the first time. It was suggested that owing to orbital angular momentum of optical vortex, clearer and smoother processed surfaces were obtained with less ablation threshold fluence, in comparison with the ablation by a nonvortex annular beam modified from a spatially Gaussian beam. (C) 2010 Optical Society of America

We demonstrated MHz-repetitive mid-infrared generation from a PPSLT-OPG pumped by a pico-second Nd:YVO4 bounce laser system. Average power of 640mW was obtained in a frequency range of 1.58-1.63μm, corresponding to a slope efficiency of 18.2%. © 2010 Optical Society of America.

We report, for the first time to our knowledge, on picosecond-pulse optical phase conjugation using photorefractive Sn2P2S6 crystals. For 7.2-ps pulses at 1.06 mu m, we have achieved phase-conjugate reflectivities of up to 45% with very fast build-up times, about 15 ms at an intensity of 23 W/cm(2) using Te-doped Sn2P2S6. We furthermore demonstrate aberration-free 5 W optical output of 8-ps pulses at 1.06 mu m from a side pumped Nd:YVO4 amplifier using the Sn2P2S6-based phase-conjugate feedback. (C) 2009 Optical Society of America

We have demonstrated a distributed-feedback plastic waveguide blue laser using Fluorescent Brightener 135 pumped by a picosecond pulse laser. The optical properties of Fluorescent Brightener 135 and its laser properties including photostability were investigated. The experimental laser slope efficiency and energy threshold were 8.2% and 24 mu J, respectively. An operation lifetime of 5,000 shots was attained under a pump pulse energy of 28 mJ at a wavelength of 355 nm. (C) 2010 The Japan Society of Applied Physics

Passively Q-switched yellow output from a frequency-doubled self-stimulating Raman composite Nd:YVO4/YVO4 laser using a Cr:YAG saturable absorber is reported. Maximum yellow output power of 264 mW was obtained with corresponding diode to yellow conversion efficiency of 5.9%.

High power passive Q-switching of a diode-side-pumped Nd:YAG ceramic bounce laser at 1.3 mu m is demonstrated. The laser operates from 18 to 114 kHz pulse repetition frequency, producing pulses of 55140 ns duration. Average output power of 5.8 W was obtained from 52 W of pump power. Five Watts of high beam quality output was also achieved in an asymmetric cavity geometry. (C) 2009 Elsevier B.V. All rights reserved.

We have demonstrated a highly efficient, long-lifetime waveguide dye laser using nanosized-particle-dispersed random scattering active media An experimental laser slope efficiency of 38.6% and energy threshold of less than 1 mu J at a single longitudinal mode were measured The operation lifetime of this laser device reached 6.5 million pump shots (C) 2009 The Japan Society of Applied Physics

We directly produced for the first time a high-power 1.06 mu m vortex mode from a diode-pumped Nd:GdVO4 bounce amplifier. A maximum output of 17.8 W was achieved for a pump power of 55 W. The corresponding optical efficiency from the diode to the output was above 30%.

We demonstrate a high average power similar to 4 ps output from a phase conjugate laser system based on a diode-side-pumped Nd:Gd0.6Y0.4VO4 bounce amplifier. An average output power of 16.2 W with a peak power of 210 kW was achieved. A corresponding extraction efficiency of 23% was measured. (c) 2008 Optical Society of America

An overview on current trends in stimulated Brillouin scattering and optical phase conugation is given. This report is based on the results of the "Second International Workshop on stimulated Brillouin scattering and phase conjugation" held in Potsdam/Germany in September 2007. The properties of stimulated Brillouin scattering are presented for the compensation of phase distortions in combination with novel laser technology like ceramics materials but also for e.g., phase stabilization, beam combination, and slow light. Photorefractive nonlinear mirrors and resonant refractive index gratings are addressed as phase conjugating mirrors in addition.

We produced a high power radially-polarized output directly from a diode-pumped Nd:YVO4 bounce amplifier, using an autocloned photonic crystal mirror as an output coupler, with a simple cavity configuration. The radially-polarized output power of similar to 6 W was achieved, and a corresponding slope efficiency was estimated to be similar to 17 %. The output was characterized to be an ideal radially-polarized beam from its polarization distribution profiles. The output mode was not an eigenmode in the resonator. We discussed and clarified intra-cavity mode dynamics in terms of polarization distribution in the wavefront. (C) 2008 Optical Society of America.

High power passive Q-switching was achieved with a pulse width of 18-32 ns by using a diode-side-pumped Nd:Gd0.6Y0.4VO4 bounce amplifier. An average output power of > 8 W was obtained at a pump power of 39 W. The peak power of the Q-switched output was adjusted within 1.9-5.2 kW by changing the Nd concentration. The mixed vanadates showed significantly higher Q-switching performances in comparison with pure Nd:GdVO4.

We report continuous-wave yellow emission from a compact Nd:YVO4 self-Raman laser with intra-cavity frequency-doubling in LBO, pumped by a 4.5 W high-brightness diode laser. A maximum yellow output of 140 mW was observed with an overall optical (diode-to-yellow) conversion efficiency of 4.4%, and with a high beam quality (M-2 similar to 1.2). A variety of different resonator configurations were investigated in order to achieve low threshold, highest output powers and efficiency, and to investigate amplitude stability.

We investigated thermal-lensing effects in a side-pumped 1.3 mu m Nd:YVO4 slab laser amplifier having a bounce geometry. The thermal-lens power during 1.3 pm laser action was 1.3-times larger than that without laser action. Excited-state absorption is the main cause for increased heat loading during laser operation. The heat-loading formula in end-pumped 1.3 mu m vanadate lasers having low Nd doping can be extended to account for heat generation in diode-side-pumped vanadate bounce lasers having high Nd doping. (c) 2007 Elsevier B.V. All rights reserved.

We demonstrated high-repetition-rate (sub-MHz) MW pulse generation by combining a picosecond phase conjugate laser system based on a diode-side-pumped Nd:YVO4 bounce amplifier with a pulse selector based on a RbTiOPO4 electro-optical modulator. Peak output powers in the range of 2.8-6.8 MW at a pulse repetition frequency range of 0.33-1.0 MHz were achieved at an extraction efficiency of 34-35%. (C) 2007 Optical Society of America.

We demonstrate direct production of a high power Laguerre-Gaussian mode from a diode-pumped Nd:YVO4 1.3-mu m bounce amplifier with an asymmetric cavity configuration. A maximum LG output of 7.7 W is obtained. (c) 2007 Optical Society of America.

We demonstrated a high power pico-second output from a diode pumped Nd:YVO4 slab amplifier with a Rh:BaTiO3 phase conjugate mirror. Over 25W diffraction-limited output was obtained. This system could also produce MW ps pulses. © 2007 Optical Society of America.

The contrast transfer function (CTF) of super-resolution microscopy was quantitatively investigated using a fluorescent scale. The scale has minute fluorescent line patterns, finer than 100 nm, and is suitable for measuring CTF in super-resolution microscopy. The measured CTF shows that super-resolution microscopy can indeed improve the optical properties of fluorescent images and enable us to observe a structure with the spatial resolution overcoming the diffraction limit. From the CTF, it has been found that super-resolution microcopy can resolve a 100 nm line-and-space pattern and provides a contrast of 10%. The CTF corresponds to a PSF with a full-width at half-maximum (FWHM) of 130 run. An evaluation using a 100 nm phi fluorescent bead consistently supports the results given by the CTF for super-resolution microscopy.

We investigated design issues for the power scaling of a pico-second Nd:YVO4 master-oscillator power amplifier system with a photorefractive phase-conjugate mirror by using standard beam propagation analysis. We also demonstrated a 25 W diffraction-limited pico-second output. A corresponding extraction efficiency of 31 % was achieved. (c) 2006 Optical Society of America.

High power operation of high repetition Q-switched ceramic Nd: YAG laser is demonstrated using a master-oscillator power amplifier with transversely-pumped bounce geometry. The laser system produced > 40W high spatial quality output (M-2 < 1.3) at a pulse repetition frequency of > 100 kHz. Pulse width of 35-80 ns was achieved in pulse repetition frequency range of 10-150 kHz. (c) 2006 Optical Society of America.

We prepare a diffraction grating composed of the gold layer on a glass plate using the gold deposition development in photographic materials and following baking process. A high-resolution image with a spatial resolution of over 4000 lines/mm was obtained. A diffraction grating composed of gold particles in a gelatin layer was prepared by development in a gold-thiocyanate complex solution. The grating was then baked to burn out the gelatin layer and fuse the gold particles. The thickness of the grating composed of the gold layer was less than 10 nm. After baking the grating had a bright gold luster and showed a clear higher-order diffraction on the reflecting side, while it showed only first-order diffraction before baking. The maximum efficiency of the first-order diffraction beam on the grating before baking was 8.8%. After baking, the maximum efficiency of the reflected diffraction beam was 1.6%. Using this method, it is possible to prepare stable holograms even in severe environments. (c) 2006 American Institute of Physics.

We have achieved high average power Raman output from a compact, diode-pumped, self-stimulating Nd3+:KGd(WO4)(2) Raman laser. Maximum Raman output power of 0.8 W was achieved at a pulse repetition frequency (PRF) of 2 kHz. The optical efficiency from diode to Raman laser was 14%. By generating extra-cavity second harmonics using a LiB3O5 crystal, it was possible to produce 0.2 W yellow output. The laser system was simulated numerically using rate equations and the results obtained were in good agreement with the experimental results. (c) 2005 Elsevier B.V. All rights reserved.

Up to 650kHz high repetition active Q-switching was achieved with a pulse-width of < 40ns by using a diode-side-pumped Nd: GdxY1-xVO4 bounce amplifier. An average output power of 17.5W was obtained at a pump power of 41W. The pulse repetition frequency range of the stable Q-switching operation was adjusted without any loss of the average output power by changing the Gd:Y mixture ratio. (c) 2006 Optical Society of America

We have demonstrated highly efficient Laguerre Gaussian beam generation by using a ring self-pumped phase conjugate mirror in the pico-second regime for the first time. The phase conjugate reflectivity was typically similar to 55%. We have also investigated the conservation of optical angular momentum. (c) 2006 Optical Society of America.

We have produced a high beam quality pico-second laser based on a continuous-wave diode pumped Nd:YVO4 slab amplifier with a photorefractive phase conjugate mirror. 12.8W diffraction-limited output with a pulse width of 8.7ps was obtained. (c) 2005 Optical Society of America.

High power operation of highly-doped ceramic Nd:YAG laser is demonstrated using a laser diode transversely-pumped bounce geometry. Using a 2% doped ceramic Nd:YAG amplifier, an output power of 45W was achieved with 158W diode pumping. The cavity configuration was optimized for TEM00 operation and a high spatial quality output (M-2 < 1.5) was obtained at an output power of 27W. A ceramic Nd: YAG laser with 4% doping was operated at over 1 watt of output power. These are the highest power levels achieved in ceramic Nd:YAG lasers at > 1% doping level. (c) 2005 Optical Society of America.

The two-point resolution of a novel two-color far-field super-resolution fluorescence microscopy was evaluated by measuring fluorescent beads 100 nm in diameter. This microscopy is based on a combination of two-color fluorescence dip spectroscopy and a phase-modulation technique for a laser beam. By simply introducing two-color laser light, the size of the fluorescent image of a bead was shrunk down to a diameter of 250 run from the diffraction-limited image with a diameter of 360 nm. For two closely adjacent fluorescent beads with a separation distance of 350 nm, the two-color microscope clearly gave separated fluorescence images, while the conventional one-color fluorescence microscope could not resolve them. It has been proved that our technique breaks Rayleigh's diffraction limit.

Thermal load in Nd3+ doped vanadate crystals with and without laser action at 1.34 mu m is investigated. Excited state absorption contributes significantly to a fractional thermal loading as well as quantum defect. (C) 2005 Optical Society of America

Efficient continuous wave (CW) and high repetition rate Q-switched operations of a laser diode transversely pumped 2% Nd-doped ceramic Y(3)A1(12)O(5)(YAG) laser in bounce geometry are presented. In CW operation 13 W of output power was produced with a slope efficiency of 40%. The average power under Q-switched operation reached up to as much as 10 W at a repetition frequency of 160 kHz. A pulse width of 24 ns was observed at repetition rate of 20 kHz and less than 100 ns across the Q-switched range of 10-160 kHz. © 2005 Elsevier B.V. All rights reserved.

We demonstrate 80 times phase conjugation by four-wave mixing of pico-second pulses in a diode-pumped Nd: YVO4 amplifier. Slight pulse broadening as a result of four wave mixing processes was observed. (C) 2005 Optical Society of America.