Tomohiro Hirose

Optical recording media using laser-induced size reduction of Au nanoparticles

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.

Diffraction Efficiency of Holographic Grating Formed in Au Nano particle-Doped Sol–Gel Silica Film by Laser Irradiation

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 ∼0.01%.

Highly efficient degenerate four-wave mixing with multipass geometries in a polymer laser dye saturable amplifier

We demonstrate the use of highly efficient degenerate four-wave mixing for phase conjugation with multipass geometries in a polymer laser dye saturable amplifier. Phase-conjugate energy reflectivity of as much as 20,000% with a four-pass geometry in the longitudinally pumped polymer dye was obtained at 564 nm.

Tunable phase conjugation by intracavity degenerate four-wave mixing in an injection-seeded solid dye laser

We demonstrate efficient degenerate four-wave mixing in a laser injection-seeded solid dye laser. Phase-conjugate energy of as much as 140 times the total energy injected externally into the phase conjugator was extracted. Moreover, efficient phase-conjugate energy was obtained in the broad wavelength region from 558 to 567 nm.

Self-diffraction of pico-second pulses in a saturable amplifier polymer dye

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.

Optical nonlinearity in gelatin layer film containing Au nanoparticles

We demonstrate a novel technique to fabricate a gelatin film containing Au-nano-particles. The technique is based on silver halide photographic development. We investigated third-order non-linearity of the film by forward-four-wave-mixing technique. Peak absorption appeared at the wavelength of 560nm. Self-diffraction by the use of third order nonlinear grating formed by intense pico-second pulses was observed. Experimental diffraction efficiency was proportional to the square of the pump intensity. Third-order susceptibility c(3) of the film was estimated to be 1.8?~10^-7esu.

Vectorial phase conjugator by degenerated four-wave mixing in a laser-pumped polymer dye amplifier

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.

Picosecond four-wave mixing in a saturable amplifier polymer dye

Summary form only given. Self-diffraction by four-wave-mixing (FWM) in a nonlinear medium such as liquid crystals and photorefractive materials can contribute to perform energy transfer between the two incident beams. FWM in a saturable gain media has received an intense attention in recent years. Owing to the amplification experienced by all the interaction beams, the high diffraction efficiency is expected. This paper presents the demonstration of transient self-diffraction by pico-second FWM in a saturable amplifier Rhodamine 6G polymer dye. In this work, we extend our previous study of FWM in an inverted polymer dye in the transient regime by using signal and pump lasers with pulse duration of much less than the population relaxation time (several nanoseconds) in the polymer dye. The polymer dye saturable amplifier is shown to be an excellent nonlinear material with high diffraction efficiency and fast response time. It has a potential for applications such as real-time holography, phase conjugation, pulse shaping, and all optical temporal-spatial conversion.

Vectorial phase conjugation by degenerate four-wave-mixing in a saturable amplifier polymer laser dye

Summary form only given. Vectorial phase conjugation (VPC) is an effective technique of eliminating phase and polarization aberrations in optical systems. Applications of VPC in visible region include optical image processing and optical computing. We present what we believe the first demonstration of visible vectorial phase conjugator (VPC) in a laser-pumped polymer laser dye Rhodamine 6G in PMMA matrix.