Kenichi Nakama

Fabrication of Micro-Optic Elements by the Sol-Gel Method

Micro-lens arrays composed of organic-inorganic materials were molded on glass substrates by the sol-gel method. Each lens had the same focal length and accurate pitch. There was no change in appearance or focal length after heat treatment at 350°C. The arrays had a refractive index of 1.53 (@1550 nm) and a transmittance of 98%/mm (@1550 nm). The film material did not change in appearance during evaluation for acid resistance.

A chemically modified glass surface that facilitates transglutaminase-mediated protein immobilization

An amino-modified glass surface for enzymatic protein immobilization by microbial transglutaminase (MTG) was developed. Diamine substrates with secondary amino groups in the linker moiety, like triethylenetetramine (TETA), exhibited at most a 2-fold higher reactivity in the MTG-catalyzed reaction compared to those with the alkyl linker. A 96-well glass plate was subsequently modified with selected diamine substrates. Validation of the modified surface by enzymatic immobilization of enhanced green fluorescent protein tagged with a glutamine donor-substrate peptide (LLQG) of MTG revealed that the protein loading onto the TETA-modified glass surface was approximately 15-fold higher than that on the unmodified one.

Laser micromachining for Ag ion exchanged glasses

Machining properties of Ag containing glasses (ACG) using KrF excimer laser and femtosecond laser are reported. Ag ions in the ACG are effective to prevent cracking and chipping during the laser machining. A 4x4 hole array fabricated by KrF excimer laser onto an ACG has good uniformity of hole diameter, d(ave) equals 129.9um and (sigma) equals 0.8um. V- and U- grooves are fabricated on ACG using a Ti:Al2O3 laser irradiation. The cross- sectional shape is controlled by Ag ion concentration in ACG.

Compact multichannel optical power monitor module for DWDM networks using a novel glass diffraction grating

A real time power-monitoring module for each wavelength channel that is suitable for guarding dense WDM (DWDM) networks and controlling an optical fiber amplifier is described. We proposed a compact real time demultiplexing channel monitor module (DCMM), which was applied to a micro-monochromator using an optimised photodetector array (PDA) and a novel sol-gel glass diffraction grating. The on board type demultiplexing channel monitor modules, which were based on the simple free space optics of the littrow mount with a low thermal expansion coefficient package, were fabricated and the optical performance estimated. From the results, it was found that the flattop and athermal characteristics of the wavelength responses were the best solution for DWDM channel monitoring systems.

New approaches to practical guided-wave passive devices based on ion-exchange technologies in glass

For the use in cost-effective optical communication systems, two types of guided-wave devices have been studied using ion exchange in glass: (1) A microlens-loaded coupler module composed of a polarization-maintaining fiber array, a directional coupler and a twin-microlens array for coherent balanced receivers has been proposed and fabricated with an excess loss of 1.0 dB and an extinction ratio of _> 20 dB for 0-60 degC operation. (2) An optimum mask pattern for splitters has been devised theoretically and verified experimentally, which has reduced the scattering loss to < .0.1 dB and also suppressed their possible bimodal behavior in the branching region.