Kenichi Yamashita

Solid state organic laser emission at 970nm from dye-doped fluorinated-polyimide planar waveguides

We have demonstrated near-infrared amplified spontaneous emission and laser emission from fluorinated-polyimide waveguides doped with an organic dye, 5,6-dichloro-2[8-(p-dimethylaminophenyl)-2,4-neopentylene-1,3,5,7-octatetraenyl]-3-ethylbenzothiazolium perchlorate (LDS950). The planar waveguides doped with 1wt% of the dye, 10mm in length and 9.3μm in thickness, have exhibited amplified spontaneous emission and optical gain around 960nm under optical pulse pumping. A good optical gain coefficient of 1.4mm−1 was obtained. Furthermore, by using the cleaved waveguide edges as reflective facets, sharp emission peaks showing laser oscillation at 970nm were observed under the optical pulse pumping. The lasing threshold was 0.22mJ∕cm2. The lasing wavelength of 970nm is the longest for solid state dye-doped polymeric lasers.

Simple fabrication technique of distributed-feedback polymer laser by direct photonanoimprint lithography

This paper describes a fabrication technique of polymeric distributed-feedback lasers using the photonanoimprint lithography. In devices with a grating structure, which was imprinted directly onto the active layer surface in vacuum, single-mode laser oscillations were easily obtained. The emission color of the distributed-feedback laser can be controlled only by changing doping material and grating period of the master mold. It was demonstrated that the nanoimprint lithography would be a key technology for development of a multicolor light source.

Low threshold amplified spontaneous emission from near-infrared dye-doped polymeric waveguide

We have investigated near-infrared light amplification in a dye-doped polymeric waveguide structure under optical pumping. Amplified spontaneous emission (ASE) at ∼800nm was observed in poly(vinyl-pyrrolidone) thin film with organic dye LDS798. The ASE threshold energy was as low as ∼12μJ∕cm2, which is about one-tenth of previously reported values for infrared-dye-doped polymeric waveguides. This low threshold ASE comes from a large Stokes shift of LDS798, in which the self-absorption of emission is suppressed.

Simultaneous RGB lasing from a single-chip polymer device

This Letter describes the fabrication and operation of a single-chip white-laser device. The laser device has a multilayered structure consisting of three laser layers. Each laser layer comprises polymer claddings and a waveguide core doped with organic dye. In each laser layer, grating corrugations were fabricated by UV-nanoimprint lithography that act as distributed-feedback cavity structures. Under optical pumping, lasing output with red, green, and blue colors was simultaneously obtained from the sample edge.

Multilayered solid-state organic laser for simultaneous multiwavelength oscillations

This paper describes an organic dye-doped polymeric laser with a multilayered structure of active waveguides. Using the technique of photonanoimprint lithography, organic active-waveguide layers with distributed-feedback cavities and a polymeric intermediate cladding layer were stacked on a silica substrate. Under optical pumping, lasing oscillations at 427 and 636 nm, which correspond to the Bragg reflection wavelengths in the respective active waveguides, were simultaneously observed. The fabrication scheme presented here is expected to be a promising technology for the development of compact multicolor laser sources.

Self-written waveguide structure in photosensitive polyimide resin fabricated by exposure and thermosetting process

A new fabrication technique of self-written waveguide was developed by using a photosensitive polyimide (PSPI) resin. The PSPI resin enables us to fabricate a solidified cladding portion of the self-written waveguide only by a thermosetting process after writing of the waveguide core. In the PSPI resin, a self-focusing effect of the exposing laser light, induced by difference in refractive index between exposed and unexposed portions, was observed. The coupling loss between two multimode fibers, which were placed with 0.5-mm gap, was decreased to 0.7 dB by insertion of the PSPI all-solid self-written waveguide. This simple fabrication method of the self-written waveguide structure is applicable to a convenient alignment technique of optical components.

Self-written active waveguide for integrated optical amplifiers

The authors propose a fabrication method of optical amplifying devices, which is based on a technique of light-induced self-written waveguide. The waveguide structure doped with infrared organic dye molecules was self-written by visible laser light irradiation from optical fiber tips to photopolymerized resin, which makes the waveguide self-aligned with input and output fibers. The self-written “active” waveguides with the length of 0.98–1.89mm were fabricated and amplified spontaneous emission at ∼790nm was observed. Furthermore, optical amplification of externally input light was also implied in a tentative examination.

Solid-state organic laser using self-written active waveguide with in-line Fabry–Pérot cavity

A polymer-based laser structure with an in-line Fabry–Perot cavity has been invented using a self-written active waveguide. This device has a channel waveguide structure doped with organic dye and can be automatically interconnected with input/output waveguide ports. The most noteworthy feature, which may provide us with a promising technology for the integrated optical circuit, is that the device can be directly fabricated between passive waveguiding components. In optically pumped emission measurements, laser emission was output from the in-line Fabry–Perot device via the interconnected optical fiber.

Propagation-mode-controlled fabrication of self-written waveguide in photosensitive polyimide for single-mode operation

We have developed a new fabrication method of single-mode self-written waveguide by controlling the propagation mode in an optical fiber. This method is very appropriate for repeatable fabrication of the single-mode self-written waveguide. Since a Gaussian-like near-field pattern is required for the fabrication of a tiny and uniform waveguide core, the propagation mode in a conventional optical communication fiber was controlled by coupling with an optical fiber having 3-/spl mu/m core, which shows a single-mode operation at visible wavelength region. Single-mode propagation at optical communication wavelength was confirmed for the fabricated self-written waveguide. The evaluated core diameter of the self-written waveguide was /spl sim/9.5 /spl mu/m.

Array of a dye-doped polymer-based microlaser with multiwavelength emission.

This Letter reports a convenient method of fabricating a polymer-based microlaser array. Laterally aligned plastic micropillars equipped with an optical resonator were fabricated by using a lithographic technique with an organic-dye-doped photopolymer, which operated as a laser element with a vertical cavity. Under optical pumping, very fine emission spectra showing a Fabry-Perot-type lasing oscillation were observed. Using this technique, integrated laser cavities with desired operation wavebands can be produced easily.