Rayleigh scattering study and particle density determination of a high refractive index TiO2 nanohybrid polymer.

We have experimentally carried out a Rayleigh scattering study of a high refractive index TiO(2) nanohybrid polymer. By employing the Rayleigh scattering technique with at least three different wavelengths, we can obtain the Rayleigh ratio of the TiO(2) nanohybrid polymer at each utilized wavelength. These measured Rayleigh ratios are then used to estimate the size of the nanoparticle and determine the number of nanoparticles per unit volume or particle density. Furthermore, this technique can be used to evaluate the dominant size of nanoparticles in the nanohybrid polymer mainly contributed to Rayleigh scattering.

Encircled Flux-based optimized simple launch condition for standardization of multimode polymer optical waveguide evaluations.

Multimode polymer optical waveguide evaluations by using a combination of multimode optical fibers (MMF) and Light Emitting Diode (LED) give very often inconsistent experimental result. It is due to the over-filled properties of the launch light created by this configuration. We propose an optimized simple launch configuration to overcome the problems by using similar configuration. The optimized launch configuration creates an optimal-filled launch light where its encircled flux (EF) profile satisfies the EF template provided by the International Electrotechnical Commission (IEC). We have used the standard optical fibers and optical fiber adaptors to create the optimized simple launch configuration with high stability. Therefore, our proposed launch configuration is suitable for realizing a cost effective optimized launch configuration for standardization of multimode polymer optical waveguide evaluations. We demonstrated reliability of the proposed launch configuration by examining the reproducibility of the insertion loss (IL) measurements. We have used two waveguide samples that have different characteristics for this purpose. It was found that the insertion loss (IL) measurements of the two samples are consistent with the largest variation of less than 5%. This variation is better than the proposed value given by the IEC that is 10%.

Refractive index control and Rayleigh scattering properties of transparent TiO2 nanohybrid polymer.

The surface of TiO2 nanoparticles (NPs) was modified by a coupling agent of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane to render them highly compatible with organic monomer mixtures avoiding aggregation. Such TiO2 NPs were then chemically attached with a prepolymer. The refractive index of hybrid TiO2 NPs-polymer was increased dramatically in comparison with that of pure polymer, and it can be controlled by adjusting the content of TiO2 NPs. The Rayleigh scattering of hybrid TiO2 NPs-polymer was size-dependent and increased with the increase of the TiO2 NPs content. When Rayleigh scattering of the hybrid material prepared with a milling and centrifuge process was significantly lowered, one can obtain a transparent sample, which is good for optical devices.

A passively mode-locked femtosecond soliton fiber laser at 1.5 microm with a CNT-doped polycarbonate saturable absorber.

We report a new 1.5 mum femtosecond fiber soliton laser incorporating a polymer saturable absorber that consists of polycarbonate (PC) with carbon nanotubes (CNTs). We installed the polymer in a fiber laser with a cavity length of 5.1 m, in which an erbium-doped fiber was used as the gain medium. Stable passive mode-locking was achieved for a pump power of 303 mW at 39 MHz, and a pulse width of 115 fs with an average output power of 3.4 mW was obtained.

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.

Operating characteristics of near-infrared self-assembled polymer microlasers.

We report near-infrared laser emission from self-assembled luminescent polymer microcavities. The microrings are formed around silica optical fibers of varying diameters (80, 125, and 200 microm) and are shown to exhibit photopumped lasing at approximately 820 nm. The microrings with 200 mum inner diameter have an overall quality factor of approximately 2 x 10(3), which is limited by surface roughness and scattering. We illustrate how the laser threshold varies inversely with both the quality factor and the diameter of the microrings. The free spectral range and the intensity variation of the laser output are also presented.

Polymer saturable absorber materials in the 1.5 microm 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.

Simple process for fabricating a monolithic polymer optical waveguide.

A simple and economical fabrication process for a monolithic polymer optical waveguide in which different materials are serially grafted is proposed and demonstrated. A cladding layer with a waveguide core groove is fabricated by microtransfer molding. An epoxy resin solution is spin coated onto the cladding before selective photoexposure to form a transparent waveguide core. An optical functional polymer solution is then spin coated to form a serially grafted waveguide structure. Thus two types of polymer fill the groove to realize a monolithically integrated waveguide. Controlling the groove shape results in a flat surface. A low connection loss between the two polymers, less than 0.01 dB/point, is obtained.

Vibrational spectra and chemical quantum calculations for 2-adamantylamino-5-nitropyridine crystals--a novel material for laser Raman converters.

Polycrystalline infrared and polarized FT-Raman spectra have been measured for 2-adamantylamino-5-nitropyridine, a novel organic material for laser Raman converters. The assignment of IR and Raman bands is given on the basis of DFT calculations. The spectroscopic studies have not indicated the presence of any significant intermolecular interactions in the crystal structure of this compound. The lines observed in the stimulated Raman spectrum of this crystal are assigned to the respective molecular vibrations.