Lanthanide-based luminescent hybrid materials.

A review was presented to demonstrate a historical description of the synthesis of light-emitting conjugated polymers for applications in electroluminescent devices. Electroluminescence (EL) was first reported in poly(para-phenylene vinylene) (PPV) in 1990 and researchers continued to make significant efforts to develop conjugated materials as the active units in light-emitting devices (LED) to be used in display applications. Conjugated oligomers were used as luminescent materials and as models for conjugated polymers in the review. Oligomers were used to demonstrate a structure and property relationship to determine a key polymer property or to demonstrate a technique that was to be applied to polymers. The review focused on demonstrating the way polymer structures were made and the way their properties were controlled by intelligent and rational and synthetic design.

Synthesis of Light-Emitting Conjugated Polymers for Applications in Electroluminescent Devices

Organic semiconductor lasers.

https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=907346

Evaluating the characteristics of multiwall carbon nanotubes

Organic dye-doped polymers have been widely investigated as gain media in solid-state dye lasers. Dye molecules which have large absorption and induced emission cross sections due to allowed π-π transitions are ideal active dopants for the generation and amplification of intense light pulses. However, continuous wave operation is not feasible with organic dyes because of the triplet losses. On the other hand, lanthanide ions that have long metastable state lifetimes are widely used in silica glass-based fiber amplifiers and for both continuous and pulsed lasers. It has been more than 30 years since the first lanthanide lasers were reported.1-3 During this period a wide variety of lanthanide lasers and amplifiers have been investigated, and extensive progress has been made by many researchers. Many reviews have been written concentrating primarily on the physical and chemical properties of lanthanides in many matrices for laser action.4-8 Recently, several books have focused on lanthanide-doped fiber amplifiers for optical communications.9-11 The success of lanthanide-doped fiber amplifiers has inspired thousands of publications and continues to motivate research on the many diverse components that are required in these systems. Optical links are now used primarily in applications such as telecommunications with single-mode silica optical fibers, which have the ability to provide high-bandwidth and long-distance communications. However, as the demand for bandwidth increases in the office and home, it has become increasingly important to develop very low cost optical links that can be readily installed by users. Plastic optical fibers (POF) have received increasing attention because of their clear technical advantages over glass fibers, such as flexibility and a large core diameter, which enables efficient connection and coupling resulting in a low-cost system for a local area network. Recently a low-loss (100 db/km), highbandwidth 5.12 GHz for 100 m transmission graded index plastic optical fiber (GI-POF) has been developed.12 Also, an all fluorinated POF, whose low loss region is extended to the visible and near-infrared, has been successfully prepared.13 Plastic optical fiber amplifiers (POFA) that generate signal light in the visible and near-infrared are potentially important because of their adaptability for POF-based short span optical local distribution networks. This review describes recent progress on plastic optical fiber lasers and amplifiers with lanthanides. We focus especially on the design and selection of plastic optical fiber and chelate materials.

Plastic optical fiber lasers and amplifiers containing lanthanide complexes.

Rare-earth chelate-doped graded index (GI) polymer optical fibers (POF) are proposed and fabricated. The attenuation loss was measured to be 0.4 dB/m at 650 nm for a GI POF doped with 1 wt % of europium (Eu) chelate. Lifetime shortening and spectral narrowing verified the occurrence of superfluorescence at 614 nm in the Eu chelate-doped GI POF pumped with xenon flashlamps. The demonstration of superfluorescence shows that rare-earth chelate-doped GI POFs are appealing as optical amplifiers and superfluorescent sources in a variety of communication and sensor applications.

Fabrication and superfluorescence of rare-earth chelate-doped graded index polymer optical fibers

A graded-index polymer optical fiber containing rhodamine 6G in poly(methyl methacrylate-co-2-hydroxyethyl methacrylate) has been fabricated. Lasing behavior of the fiber was observed by pumping with a frequency-doubled Q-switched Nd: yttrium–aluminum–garnet laser. A slope efficiency of 43% and a lifetime of 110 000 shots at a repetition rate of 10 Hz have been observed. With a 1.5 mJ pump energy, an output energy of 640 μJ was produced.

High-efficiency organic dye-doped polymer optical fiber lasers

Van Hove singularities (VHS) in the density of states of multiwalled carbon nanotubes (MWNTs) have been observed by optical spectroscopy for the first time to the authors' knowledge. Additionally, unexpected visible luminescence has been observed on photoexcitation at 1064 nm. This luminescence is believed to arise from radiative transitions between energy states in the VHS. A mechanism describing the underlying processes, which involve multiphoton absorption followed by upconverted luminescence from VHS energy states, is presented. Our results show that the presence of VHS readily facilitates efficient optical transitions in

Nonlinear photoluminescence from van Hove singularities in multiwalled carbon nanotubes

We have demonstrated optical gain and laser emission in multimoded plastic waveguides containing a near-infrared-emitting compound, 2-(6-(4-dimethylaminophenyl)-2,4-neopentylene-1,3,5-hexatrienyl)-3-methyl-benzothiazolium perchlorat. The poly(1-vinyl-2-pyrrolidone)-base planar waveguides, 1cm in length and 50μm in thickness, doped with 0.5wt% of the compound have exhibited lasing at 820nm under transverse nanosecond photoexcitation at 532nm. Optical feedback is provided by the 4% reflective facets of the cleaved waveguide edges. The threshold for lasing is found to be 128±30μJ∕cm2 (25.5±5.9kW∕cm2). Gain spectroscopy has shown a moderate net modal gain of 2.6±0.3cm−1 (11.3±1.3dB∕cm) at 820nm for the pump fluence of 115μJ∕cm2 (23.1kW∕cm2). Our results will open the door to the study and development of compact plastic waveguide lasers and amplifiers operating in the near-infrared region.

Near-infrared laser emission from luminescent plastic waveguides

We present the results of a study of frequency upconversion of femtosecond optical pulses in a step-index polymer optical fiber that uses a stilbenoid compound as an active dopant. Intense blue emission is observed in the doped poly(methyl methacrylate) (PMMA) fiber when it is longitudinally pumped at 800 nm by 175 fs optical pulses. By means of the intensity-dependent transmission method, the two-photon absorption cross-section is deduced. Our study illustrates that the combination of a well-designed organic chromophore incorporated into a fiber geometry is appealing for the development of an upconversion blue polymer laser.

Takeyuki Kobayashi

Papers

Fabrication and superfluorescence of rare-earth chelate-doped graded index polymer optical fibers

High-efficiency organic dye-doped polymer optical fiber lasers

Nonlinear photoluminescence from van Hove singularities in multiwalled carbon nanotubes

Near-infrared laser emission from luminescent plastic waveguides

Frequency Upconversion of 800 nm Ultrashort Pulses by Two-Photon Absorption in a Stilbenoid Compound-Doped Polymer Optical Fiber†