Kyoji Komatsu

Polymer saturable absorber materials in the 1.5 μm band using poly-methyl-methacrylate and polystyrene with single-wall carbon nanotubes and their application to a femtosecond laser

We report saturable absorber materials in the 1.5 microm band that consist of poly-methyl-methacrylate (PMMA) and polystyrene (PS) polymers with single-wall carbon nanotubes (SWNTs). A very uniform dispersion of SWNT in PMMA and PS polymers has been realized by using chlorobenzene or tetrahydrofuran as a dispersion solvent. These materials, which are as thick as 1 mm, are easily optically polished on both surfaces. This was difficult to achieve with previous thin-film materials. By incorporating PMMA/SWNT as a saturable absorber, a 171 fs pulse is successfully generated in a passively mode-locked fiber laser.

Size Control of Polydiacetylene Microcrystals

Aiming at the preparation of nanometer-size polydiacetylene microcrystals, the crystallization process during reprecipitation method was investigated using electron micrographs and light-scattering technique. We found that an amorphous nanoparticle was formed initially and subsequently crystallized. We conclude that amorphous nanoparticles must be sufficiently small in order to achieve nanometer-size crystals.

Fabrication of three-dimensional calixarene polymer waveguides using two-photon assisted polymerization

Low-loss three-dimensional (3D) polymer optical waveguide was fabricated using a two-photon assisted polymerization method. Calixarene derivatives were selected as core material with good thermal stability and transparency. To fabricate 3D waveguide, photopolymerizable polymers composed of two types of monomers were used. Core shape was controlled by adjusting an astigmatism of objective lens. Refractive index difference between a core and a cladding was formed by exclusion effect of one monomer. Propagation loss at 1.3μm wavelength was low, 0.72dB∕cm, without using deuterium or fluorine but using hydrogen. Using this technique, 3D 1×3 splitter polymer waveguide was fabricated.Low-loss three-dimensional (3D) polymer optical waveguide was fabricated using a two-photon assisted polymerization method. Calixarene derivatives were selected as core material with good thermal stability and transparency. To fabricate 3D waveguide, photopolymerizable polymers composed of two types of monomers were used. Core shape was controlled by adjusting an astigmatism of objective lens. Refractive index difference between a core and a cladding was formed by exclusion effect of one monomer. Propagation loss at 1.3μm wavelength was low, 0.72dB∕cm, without using deuterium or fluorine but using hydrogen. Using this technique, 3D 1×3 splitter polymer waveguide was fabricated.

Serially grafted polymer optical waveguides fabricated by light-induced self-written waveguide technique

Serially grafted polymer optical waveguides were fabricated by the light-induced self-written (LISW) waveguide technique for the first time to our knowledge. To realize functional waveguide cores by the LISW technique, transparent materials at the writing wavelength were selected. By inserting thin transparent partitions, a serial-graft structure consisting of passive and active waveguides without any misalignment was realized automatically. This technique is advantageous for its extremely easy process over conventional fabrication techniques.

Serially grafted optical waveguide fabrication of NLO polyimide and transparent polymers

We have investigated polymers suitable for fabricating serially grafted optical waveguide with nonlinear optical (NLO) polyimide (PI). UV cured epoxy resins were appropriate not only as a cladding layer for the NLO PI but also as a core layer of the grafted waveguide. By using NLO PI as an active core layer and the UV cured epoxy resins as a passive core layer, serially grafted waveguide was fabricated. The scattering loss of the serially grafted points was relatively small. The serially grafted waveguide is applicable to many types of practical optical circuits.

Thermo-optic controllable hybrid photonic polymers containing inorganic nanoparticles

In order to control thermo-optic (T-O) coefficient of polymer materials, a hybrid polymer system with inorganic nanoparticles was examined. Because polymer materials have high T-O coefficient with low refractive index and inorganic materials have low T-O coefficient with high refractive index, we hybridized these materials. For that, surface-treated inorganic nanoparticles were dispersed into epoxy polymers to make homogeneous composites. Thus, by increasing inorganic nanoparticle contents, the refractive index of the hybrid polymer was changed, and its T-O coefficient was well controlled.

A three-dimensional polymeric optical circuit fabrication using a femtosecond laser-assisted self-written waveguide technique

We demonstrated a femtosecond pulse laser-assisted self-written waveguide technique that can fabricate three-dimensional (3D) optical waveguides in a photopolymerizing resin. A 488nm Ar+ laser and an 800nm pulse laser were used in this technique. Using the femtosecond laser scanning technique, two optical fibers were connected three dimensionally by a waveguide. The alignment-free aspect of the light-induced self-written waveguide-fabrication technique and the possibilities of 3D waveguide creation inherent in the femtosecond laser polymerization technique were combined to yield a highly versatile technique for the fabrication of 3D waveguides.

Near-infrared luminescent polymer waveguide with a 20dB small-signal gain

Near-infrared optical gain in luminescent polymeric slab asymmetric waveguides has been investigated by use of amplified spontaneous emission. Upon nanosecond photopumping, the waveguides have shown a small-signal gain coefficient of 37.2±2.1cm−1 at 820nm for a pump fluence of 1.57mJ∕cm2 (314kW∕cm2). The loss coefficient and transparency fluence have been found to be 7.3±1.0cm−1 at 820nm and 0.14mJ∕cm2 (28kW∕cm2), respectively. Furthermore, we show that a small-signal gain of 19.7±2.3dB is achievable in a 1.2-mm-long waveguide.

Enhancement of luminescent intensity of calixarene-oxetane polymer doped with europium complex

Calixarene molecules are originally known as inclusion compounds in host-guest chemistry, which can bind various metal ions and organic molecules. We investigated the binding property of calixarene polymer against trivalent europium (Eu3+) complex which possesses excellent luminescent characteristics. An interaction, i.e. coordination structure, is established between calixarene polymer and Eu3+ complex, which results in an effective suppression of concentration quenching of Eu3+ complex and enhancement of luminescent intensity in high concentration.

Oriented thin film fabrication of organic non-linear optical crystals

Abstract Ordered thin films of organic non-linear optical crystals, 4-(4-dimethylaminostyryl)-1-methylpyridinium tosylate (DAST), 2-adamantylamino-5-nitroprydine (AANP) and 3-methyl-4-methoxy-4′-nitrostilbene (MMONS), have been fabricated by a novel simple technique where their microcrystals were dragged on the glass plate. Thickness of the ordered thin film was approximately 100 nm. In ordered DAST thin film, ab-plane appeared as their surface layer. They showed dichroism in polarized ultraviolet and visible absorption spectra measurements.