Soichiro Omi

Highly photo-stable dye doped solid-state distributed-feedback (DFB) channeled waveguide lasers by a pen-drawing technique

Pyrromethene dyes doped polymeric channeled waveguide lasers with permanent DFB structures were fabricated via a novel pen-drawing technique with the patterned polydimethylsiloxane (PDMS) chips fabricated through a casting process as the substrates. With the high resolution dispensers, dye doped high viscosity pre-polymers were written into the PDMS grooves and the cross-section of the channeled waveguides could be controlled by both the polymer composition and the pen-drawing parameters. Highly stable laser output with 4.8 × 10(6) pulses of laser lifetime at 500 Hz of pump repetition rate has been obtained, which is suggested to be among one of the best results of pyrromethene 567 (PM567) up to date.

Intensity Sensitive Organic Photodiodes Patterned by Inkjet Method

In this work, intensity sensitive organic photodiodes were made based on the drop-on-demand piezoelectric inkjet printing of poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) blend on the ITO substrates. Inkjet conditions for printing the P3HT:PCBM/chlorobenzene solution were studied and the influences of concentration and inkjet parameters such as pulse voltage and the method of stacking spots were systematically investigated under the goal of optimizing the morphology and uniformity of P3HT:PCBM spots on various kinds of ITO substrates. P3HT:PCBM films in any shape and size were prepared by overlapping the neighboring spots and bulk heterojunctions were fabricated after the deposition of a thin Al film as cathode on their top. Under the excitation of a 532 nm pulse laser source, the open-circuit voltage (Voc) between the ITO and Al electrodes could be detected. Intensity sensitive photo-diodes were obtained with a quantum yield of ∼0.35% and the time constant was estimated to be ∼1.0 μs. Ways for further improvement on the performance of the photo-diodes were also suggested.

Development of print-like-fabrication techniques for distributed feedback solid state dye lasers with multiple-layered structure

Novel fabrication technique of organic solid state waveguide dye laser has been developed for easy fabrication and surface integration. Polymeric waveguides fabrication based on dispensing and drawing scheme can control a refractive index with 0.001 resolution and can stack multiple-layer just in a limited area. It can realize more complicated laser system in comparison with our previous technique. New proposed DFB laser with Quasi-Mode-Coupled were also demonstrated in improve performance.

Monochromatic organic photodiodes made by stackable ink-jet fabrication for integrated laser chips

Organic photodiodes were made by ink-jet method based on the J-aggregated cyanine dye films. The radiation sensitivity and spectral resolution were improved significantly by approaches, indicating the realization of integrated flow-cytometry chips.

Development of multicolor DFB dye laser by Transversal Quasi-Mode-Coupling method

Multicolor laser array, a novel type of pumping method, Transversal-Quasi-Mode-Coupring on waveguide laser was demonstrated Four color laser array was demonstrated by experiments.

Degradation recoverable DFB lasers based on P597:PDMS/PTFEMA

Organic materials are promising candidates for integrated optical waveguide because of their ease of fabrication, flexibility, compatibility with many kinds of photonic and electronic functional molecules. The solid-state dye laser active media such as dye doped glasses or polymers have been proposed by many research groups. However, materials with low optical loss in the visible and near-infrared regions have been combined with fluorescent dyes, and these indicate short durability. Recently, we found that PDMS (Polydimethylsiloxane) is a long durability solid-state dye laser host matrix. The reason is the possible circulation of dye molecules in PDMS by its nano structure. “PDMS-state” dye laser media have both shape maintainability and dye circulation in solid-state and liquid-state media, respectively. Moreover, it is easy to fabricate PDMS waveguides by the pen-drawing technique [1]. Previously, some researches on waveguides using PDMS have been investigated [2]. In this study, we demonstrated a solid-state polymer laser with self dye-circulatory function by PDMS waveguide. After pumping a DFB laser, an intensity of DFB laser output was recovered to 100% by dye diffusion in PDMS at room temperature. The laser was also oscillated with the single mode using spin-coated DFB layer on PDMS with tunability.

Tunable waveguide dye laser on a plastic optical fiber

The tunable waveguide dye laser on the plastic optical fiber (POF) was developed. Narrowband spectrum DFB laser operation of the dye laser pumped from optical coupling between optical fiber to the dye laser can be obtained, and wavelength modification with bending of the fiber can be observed.

Spectroscopic properties of J-aggregated cyanine in micro-sized film by ink-jet spotting

In this work, a drop-on-demand piezoelectric ink-jet system has been employed to fabricate disposable photodiodes as the detectors on the integrated lab-on-chip lasers. J-aggregated films of a cyanine dye, doped into a conductive polymer, poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate) (PEDOT:PSS) on the indium tin oxide (ITO) substrate have made by the ink-jet method, respectively. The influence of ink-jet single dot local area and spot thickness by spot stacking on the J-aggregate formation and also the wavelength sensitivity of the photodiodes have been systematically investigated and reported.

Wavelength resolution improvement on organic photodiodes made by ink-jet technique

In this work, a drop-on-demand piezoelectric ink-jet system has been employed to fabricate disposable photodiodes as the detectors on the integrated lab-on-chip lasers. J-aggregated films of a cyanine dye, NK-1952 doped into a conductive polymer, poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate) (PEDOT:PSS) on the indium tin oxide (ITO) substrate have made by the ink-jet method, respectively. With the thin Al layer on the top of cyanine dye films as the cathode, while ITO substrate as the anode, the photodiodes have been demonstrated to be wavelength sensitive under the excitation of a tunable pico-second laser, which corresponds to the characteristic red-shifted, sharp and narrow J-aggregate absorption peak of each cyanine dye employed. The influence of ink-jet fabrication parameters, presence of metal ions and pH value of dye solutions on the J-aggregate formation and also the wavelength sensitivity of the photodiodes have been systematically investigated and the mechanisms involved have been discussed. It is found that by optimizing the ink-jet fabrication parameters such as UV exposure dose amount, and substrate temperature, or by introducing ions such as K+, Na+, or H+, the wavelength resolution of the ink-jet printed photodiodes can be improved significantly, and wavelength resolution of less than 0.1nm may be expected.