尾松 孝茂

We demonstrated a 44 W near diffraction-limited pico-second output from a phaseconjugate laser system in combination with a diode-side-pumped Nd:GdVO4 booster amplifier. Peak power of 0.35 MW was achieved. © 2008 Optical Society of America.

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.

We presented a dual-layered waveguide dye laser including a random active layer with nanoparticle doping. A slope efficiency of 12.0% and an energy threshold of 0.34 μ J were obtained in a single-longitudinal-mode operation. (C) 2005 American Institute of Physics.

Efficient frequency extension of a diode-side-pumped, Q-switched 1064 nm Nd:YAG laser generating similar to5 W at 5 kHz has been demonstrated by way of intracavity SRS in crystalline Ba(NO3)(2) (1197 nm), KGd(WO4)(2) (1158 nm and/or 1177 nm), LiIO3 (1156 nm) and PbWO4 (1170 nm). (C) 2004 Elsevier B.V. All rights reserved.

We present a full characterization of a pico-second pulse generation from a Nd:YVO4 double-pass amplifier with a phase-conjugate mirror based on a photorefractive BaTiO3 crystal with an external loop geometry. With this system, 7.4 W diffraction-limited pico-second output was generated. A corresponding optical extraction efficiency of >20% was achieved.

We have demonstrated a novel technique for Au-nano-particle production in a polymer thin film based on the pico-second ultraviolet laser deposition. The Au-nano-particles produced by this technique were finely controlled without aggregation and the average size was similar to20 nm. We also investigated holographic grating formation in the polymer film by pico-second ultra-violet laser deposition technique. (C) 2004 Elsevier B.V. All rights reserved.

The formation of a doughnut-shaped laser beam is presented. To generate the beam, we use an optically addressed parallel-aligned nematic liquid-crystal phase spatial light modulator (PAL-SLM), and observe the shape of the focused beam. By using a compensating technique for wave aberration, the beam has a symmetric doughnut shape with a hole size of 1 mumphi on the focal plane. The experimental result shows that the generated beam can be expected to be applicable to super-resolving microscopy based on the fluorescence depletion process. (C) 2004 Society of Photo-Optical Instrumentation Engineers.

We demonstrate 2.5 times phase conjugation by four-wave-mixing with the use of pico-second pulses in a rhodamine6G dye polymer amplifier. Phase conjugation pulse shortening by a factor of 2 is also measured. (C) 2004 Optical Society of America.

Efficient self-stimulated Raman output from a laser diode transversely-pumped Nd3+:KGd(WO4)(2) laser is presented. The maximum Raman output energy of 340 muJ was obtained at 1.18 mum. The corresponding optical efficiency from diode output to the Raman output was estimated to be 2.7%. Yellow output was also generated by intra-cavity second harmonic generation. Up to >90 muJ was obtained. (C) 2003 Elsevier B.V. All rights reserved.

We investigated an organic waveguide laser amplifier with grating couplers based on light-induced surface grating hologram. Optical coupling efficiency to the film was approximately 0.5%. The amplifier exhibited small-signal gain of 0.5 cm(-1). (C) 2003 Published by Elsevier B.V.

Pronounced separation (750 nm) between two individual fluorescence spots in a novel super-resolution microscopy based on a two-color up-conversion fluorescence depletion technique has been investigated. This microscopy has the potential to achieve a spatial resolution (< 300nm) of 1/2 the diffraction limit. (C) 2003 Optical Society of America.

We demonstrate >4 W and 7.2 ps output of a double-pass Nd:YVO4 slab amplifier with a photorefractive ring phase conjugate mirror. A double-pass Gain of 190 and optical extraction efficiency of >20% were obtained. The amplified signal beam exhibits a TEM00 profile with beam propagation parameters M-x(2) < 1.4 and M-y(2) < 1.1.

By using a two-color dip-spectroscopy, we measured the fluorescence intensity from tryptophan in a water solution. The fluorescence intensity exponentially decreased as the laser intensity for the S-n <-- S-1 excitation increased. The phenomenon was analyzed by a rate-equation for a three-state model. The analysis shows that tryptophan with the Sn state has a radiationless relaxation process without any process through the S-1 state, and that the S-n --> S-1 internal conversion does not have a 100% yield. The branching ratio of the process is estimated to be 20%. The presented result clarifies in detail the real meaning of Kasha's rule. (C) 2003 Elsevier Science B.V. All rights reserved.

We have demonstrated a realistic super-resolution scanning fluorescence microscope using conventional nanosecond lasers. This super-resolution microscope is based on the combination of two-color fluorescence dip spectroscopy and shape modulation to a doughnut beam. Only by introducing a doughnut erase beam, the resolution of the laser fluorescence microscope breaks the diffraction limit by two times without using any mechanical probe. (C) 2003 Elsevier Science B.V. All rights reserved.

We investigated the diffraction efficiency of the holographic grating formed in the Au-nano particle-doped sol-gel film by irradiation using a frequency-doubled pico second Nd:YAG laser. The experimental diffraction efficiency obtained was similar to0.01%.

By using holographic shear interferometry, we have measured the thermal lens in a diode-pumped Yb:YAB crystal, under lasing and non-lasing conditions, as a function of absorbed power. From these purely optical measurements we estimate the fractional thermal loading and the thermal conductivity of Yb:YAB. Knowledge of these thermal parameters is essential for the optimisation of Yb:YAB laser cavity designs.

We investigate a polarization state fixer that produces light with an arbitrary desired polarization state and constant power from an arbitrary elliptically polarized input light whose principal polarization axis fluctuates randomly. An example of such a device composed of a quarter-wave plate and a polarizer is proposed, and its characteristics at wavelengths of 633 nm and 1550 nm are demonstrated. We conclude that we cannot obtain a passive device that produces fixed-axis, linearly polarized light with a constant power level from an elliptically polarized light with a varying elliptical parameter. (C) 2003 Optical Society of America.

We have combined the up-conversion-depletion technique of a dye molecule with the laser scanning fluorescence microscope. Three times higher resolution beyond the diffraction limit has been achieved. ©2003 Optical Society of America.

We investigate a polarization state fixer that produces light with an arbitrary desired polarization state and constant power from an arbitrary elliptically polarized input light whose principal polarization axis fluctuates randomly. An example of such a device composed of a quarter-wave plate and a polarizer is proposed, and its characteristics at wavelengths of 633 nm and 1550 nm are demonstrated. We conclude that we cannot obtain a passive device that produces fixed-axis, linearly polarized light with a constant power level from an elliptically polarized light with a varying elliptical parameter. © 2003 Optical Society of America.

We present what to our knowledge is the first demonstration of self-pumped phase conjugation in a laser-pumped solid-state Rhodamine-6G dye saturable amplifier. Phase-conjugate energy reflectivity of as much as 2100% at 557 nm has been obtained.

The high phase-conjugate reflectivity of 150, by four-wave mixing in a diode-pumped Nd:YVO4, has been demonstrated. The phase-conjugate mirror was capable of correcting the phase aberration of a probe beam. The experimental diffraction efficiency of the transmission gratings was 60.

An effective spatial resolution enhancement method for distributed strain measurement by BOTDR is proposed. An optical fiber is glued to a structure by a length less than the spatial resolution defined by the pulse width, and the Brillouin spectrum of the light scattered from the glued optical fiber is investigated theoretically. The apparent strain x(p) observed in the fiber is found to be proportional to the accurate strain a. The ratio r = x(p)/a coincides with the ratio of the glued length to the spatial resolution. Spatial resolution as small as 0.2 m is demonstrated experimentally for small strains of less than 10(-3).

We present efficient self-diffraction of pico-second pulses in a solid-dye saturable amplifier. Experimental second-order (2nd-order) diffraction efficiency of as much as 5% at the wavelength of 560 nm was obtained. (C) 2002 Elsevier Science B.V. All rights reserved.

Laser oscillation of a diode-pumped Nd:YVO4 phase conjugate resonator with a photorefractive ring phase conjugate mirror has been demonstrated. A 7.5 W continuous-wave (CW) output with high beam quality was obtained. Slope efficiency of 46% and optical extraction efficiency of 33% were achieved. Standard variance of the output power fluctuation was 2.3%.

BOTDR (Brillouin optical-fiber time domain reflectometry) is a promising technique for measuring the strain distribution along an optical fiber which can be used for diagnosing civil structures. However, there is a trade-off between the spatial and the frequency resolutions, and its practical spatial resolution is limited to about I in; to date the application scope has been restricted. In order to enhance the spatial resolution without decreasing the measurement accuracy, we intentionally introduce two kinds of strain within the spatial resolution length determined by the optical pulse width, which results in Brillouin gain spectrum separation. In this paper, we describe the theoretical analysis of the spectrum separation method together with experimental verification, where a spatial resolution of 0.5 in is demonstrated. We further propose a new parabolic data fitting, method especially effective in the spectrum separation method.

We present a highly bright output radiated from a single-stripe high power laser diode, known as a broad-stripe laser diode (BS-LD) with ring-type self-pumped phase conjugate mirror. Within a minute after the laser turning on, the Iasing frequency was locked at the central wavelength of 808.9 nm within 0.1 nm. The BS-LD then generated a single-lobed far-field.

Phase conjugation using degenerate four-wave mixing in a solid-dye laser was demonstrated. Laser was used as the nonlinear material and the counter-propagating pump beams were automatically provided by laser oscillation. Population inversion was obtained by longitudnal laser pumping from both sides of solid laser dye with a frequency-doubled Q-switched Nd:YAG laser. The measured phase conjugate reflectivity was 1-2% over the full external gain-pump fluence.

We present the first demonstration, to the best of our knowledge, of a vectorial phase conjugator performed in a laser-pumped Rhodamine6G doped solid-dye amplifier. A maximum phase conjugate reflectivity of 22% was obtained. The vectorial phase conjugate fidelity was higher than 0.96. (C) 2001 Published by Elsevier Science B.V.

We demonstrate a 7.8 W high beam quality continuous-wave output of a double-pass Nd:YVO4 slab amplifier with a photorefractive ring phase conjugate mirror. Optical extraction efficiency of 33% was obtained. Build-up time of the output of the amplifier was 10 s. Standard variance of the output power fluctuation was 2.6%. (C) 2001 Elsevier Science B.V. All rights reserved.

Silica-gel films containing Au nanoparticles were fabricated by a photoreduction method, which functioned as a medium for high-density optical recording. On irradiation of 532 nm laser light, which corresponds to the surface plasmon resonance absorption of Au particles, the absorption spectrum of the film showed a blueshift. Using this property, a hologram was recorded on the film. Transmitting electron microscopy supported that the change in absorption spectrum was due to size reduction of embedded particles caused by laser irradiation. For recording the hologram, a threshold of laser fluence existed which corresponded to the heat of vaporization of Au particles. (C) 2001 American Institute of Physics.

A laser diode transversely pumped compact, passively Q-switched, self-stimulating Nd3+:PbWO4/Cr4+ :YAG Raman laser is proposed. With 4.5 mJ diode pumping, fundamental and Raman output energies of 2 and 2.5 muJ have been obtained simultaneously at 1.058 and 1.17 mum, respectively. The frequency conversion efficiency is estimated to be 56%. The Raman pulse width of 8 ns is 40% of the fundamental laser pulse width of 20 ns. (C) 2001 Elsevier Science B.V. All rights reserved.

We present a new all-optical technique to measure the thermal conductivity of laser crystals. This technique can be used for crystals that are too small for direct measurement of thermal conductivity. We used this technique to measure the thermal conductivities of Nd:LYAB, with the result of 44 +/- 6% compared with that of Nd:YAG thermal conductivity. (C) 2001 Optical Society of America.