Molecularly imprinted polymer-coated hybrid optical waveguides for sub-aM fluorescence sensing.

The sensitivity of fluorescent sensors is crucial for their applications. In this study, we propose a molecularly imprinted polymer (MIP)-coated optical fibre-hybrid waveguide-fibre sensing structure for ultrasensitive fluorescence detection. In such a structure, the MIP coated-hybrid waveguide acts as a sensing probe, and the two co-axially connected optical fibres act as a highly efficient probing light launcher and a fluorescence signal collector, respectively.

Molecularly Imprinted Polymer-Coated Optical Waveguide for Attogram Sensing.

Ultrahigh sensitivity and selectivity are the ultimate goals of sensor development. For such purposes, we propose a sensing platform in which an optical fiber-waveguide-fiber (OFWF) structure is integrated with a molecularly imprinted polymer (MIP). The OFWF works as a highly efficient probe light launcher and signal light collector, and the MIP layer acts as a highly selective and sensitive sensing interface.

One-Drop Self-Assembly of Ultra-Fine Second-Order Organic Nonlinear Optical Crystal Nanowires.

In this study, we propose a one-drop self-assembly method, which proved capable of successfully preparing 4-N, N-dimethylamino-4'-N'-methyl-stilbazolium tosylate (DAST) single-crystalline nanowires (NWs). The apparent roughness of the DAST NWs was determined to be less than 100 pm by using a high-resolution atomic force microscope, indicating their ultrafine quality. The DAST NWs also exhibited excellent nonlinear optical properties, including two-photon excited fluorescence and second harmonic generation, which could enable the production of low-cost, low-power-consumption wideband wavelength conversion devices.

Camera sensor platform for high speed video data transmission using a wideband electro-optic polymer modulator.

In this work, 1 GHz video data was collected by a CMOS camera and successfully transmitted by the electro-optic (EO) modulator driven by an external modulation module integrated onto the same chip. For this application, the EO modulator component included a polymer waveguide modulator, which performed a 20 GHz bandwidth, clear eye diagram opening with a Q factor of 10.3 at 32 Gbit/s and a drive voltage of 1.

Ultra-Broadband THz Antireflective Coating with Polymer Composites.

Achieving an ultra-broadband range is an essential development direction in terahertz techniques; however, a method to cover the full terahertz band by using a highly efficient antireflection (AR) coating that could greatly increase the efficiency of terahertz radiation is still lacking. It is known that structures possessing a graded-index profile can offer a broadband AR effect, and such structures have been widely used, especially in the visible range. In this paper, first, we tuned the refractive index of a cyclo-olefin polymer (COP) by using a TiO₂ dopant, and a polymer⁻TiO₂ composite with a refractive index of 3.

Light-induced self-written waveguide fabrication using 1550 nm laser light.

Light-induced self-written (LISW) optical waveguides were fabricated for the first time, to the best of our knowledge, using a photopolymerizable resin system formed by 1550 nm pulse laser light. A two-photon absorption (TPA) chromophore with a TPA cross section of several hundred Goeppert-Mayer (GM) at 1550 nm was used. Furthermore, the optical interconnection between a single-mode fiber and a fiber Bragg grating was demonstrated by the present technique, using one-way irradiation of 1550 nm laser light through the single-mode fiber.

Launch light dependency of step-index multimode fiber connections analyzed by modal power distribution using encircled angular flux.

The propagating modal power distribution (MPD) of step-index multimode fibers (SI-MMFs), which strongly influences the performance of systems and components composed of these fibers, has not often been discussed, because, until recently, there has been no definition to show the MPD. Encircled angular flux (EAF) is a newly developed metric for defining the MPD in step-index multimode waveguides including fibers standardized by the International Electrotechnical Commission. Using the combined analysis of EAF and insertion loss, we studied the launch light dependency of SI-MMF connections.

0.1-20 THz ultra-broadband perfect absorber via a flat multi-layer structure.

An ultra-broadband perfect absorber based on graded-index mechanism is designed and fabricated. The perfect absorber is comprised of a heavily-doped silicon absorption substrate and a flat six-layer antireflective structure. The refractive index of each layer was widely tuned by hollow polystyrene microsphere and TiO nanoparticle dopants, which can offer a gradually changed refractive index profile from 1.

DAST single-nanometer crystal preparation using a substrate-supported rapid evaporation crystallization method.

A substrate-supported rapid evaporation crystallization (SSREC) method was used to develop a highly nonlinear optical material, 4-N,N-dimethylamino-4'-N'-methyl-stilbazolium tosylate (DAST), which satisfies the Rayleigh scattering requirement for the fabrication of highly transparent composites. DAST nanocrystals have a second harmonic generation active crystal structure and a high signal-to-noise ratio second harmonic generation signal when excited by using a 1064 nm cw laser. The nanocrystals also possess size-dependent UV-vis absorption and fluorescence behavior which is not seen in the bulk state.

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.

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.

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.

Single-pulse ultraviolet laser recording of periodically poled structures in polymer thin films.

A simple fabrication technique for nonlinear polymeric optical waveguide patterns is introduced based on the two-beam interference method. We determined that the second-order nonlinearity of poled polymer films is erased by single-pulse ultraviolet (UV) laser irradiation. The erasure mechanism for second-order nonlinearity is discussed.

Polarization-multiplexed optical memory with urethane-urea copolymers.

We present a polarization-multiplexed optical memory with urethane-urea copolymers. The side chains of the urethane-urea copolymers induce cis-trans isomerization by illumination of blue or green light, and they align perpendicular to the linear polarization of the illuminated light, thus producing optical anisotropy. We found that the material showed selective anisotropy for the particular direction that was perpendicular to that of the recording beam polarization.

Fabrication Technique of a Nonlinear Optical Structure Using Optical Polymeric Films by Direct Electron-beam Irradiation.

A simple fabrication technique of nonlinear optical structures for use with dye-doped polymer is described. Polymethylmethacrylate, U-100 polymer, and polystyrene were used as the host matrices to fabricate the nonlinear optical waveguide. The periodically poled nonlinear optical polymer structures and ridge-type channel structures were fabricated by direct electron-beam irradiation.

Ultraviolet photobleaching process of azo dye doped polymer and silica films for fabrication of nonlinear optical waveguides.

We describe the effect of UV photobleaching of poled polymer and silica films and the application of UV photobleaching to waveguide-type optical devices. Disperse Red 1-doped poled polymer and silica films with large and stable second-order nonlinearity were used as nonlinear optical materials. We investigated the mechanism of UV photobleaching of poled films by the changes in absorption spectrum and nonlinearity and refractive index.

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.

Direct electron-beam irradiation: a new technique for the erasure of second-order nonlinearity and the fabrication of channel waveguides by use of optical polymeric films.

We demonstrate a novel and simple technique for fabrication of a nonlinear-optical polymeric waveguide device by direct electron-beam irradiation. To form a periodically poled nonlinear-optical polymer waveguide, we exposed dye-doped polymer films directly to electron beams with an energy of 25keV. It became clear that irradiation with electron beams erased the second-order nonlinearity of poled polymer film.

Self-adaptive spatial filtering by use of azo chromophores doped in low glass-transition-temperature polymers.

We report on self-adaptive spatial filtering by combination of the self-adaptive polarization-rotation property of Disperse Red1-doped polymers with low glass-transition-temperature and Fourier-transform operation. Our system can be operated with only an action beam with object information and without a probe beam for image readout. Edge enhancement by the action beam-probe beam is demonstrated as an example of the system's application to spatial filtering.

Reflection-type confocal readout for multilayered optical memory.

We present a multilayered optical memory for use in reading data with a confocal reflection microscope system. We use a recording medium in which photosensitive thin films and nonphotosensitive transparent films are stacked alternately. Since the photosensitive films are thinner than the depth of focus of the recording beam, the spatial frequency distribution of the recorded bit data is extended in the axial direction.

Simultaneous process of embossing and poling at elevated temperatures: a simple technique for nonlinear grating formation in polymer films.

A simple technique for fabrication of nonlinear gratings in polymer films, based on simultaneous embossing and poling, is proposed and demonstrated. A master grating consisting of a metal electrode with a dielectric die was fabricated and used for repeated embossing of the grating structures into nonlinear optical polymers at elevated temperatures. At the same time, we applied high voltage to the polymer films to induce second-order nonlinearity.

Low-loss polymeric optical waveguides with large cores fabricated by hot embossing.

A simple low-cost method of fabricating polymeric optical waveguides with large core sizes for plastic optical fibers is presented. The waveguides are fabricated by hot embossing with an ultraviolet-cured epoxy resin stamper. The stamper is fabricated by replication of a rectangular groove mold that is made from silicone rubber replicated from a ridged original silicon master.

Non-optically probing near-field microscopy with illumination of total internal reflection.

We have developed a non-optically probing near-field microscope with illumination of total internal reflection. Because the illumination light does not pass through the specimens, it is possible to observe thick specimens or highly absorptive materials. It reduces the background noise because the decay length of the evanescent wave is a few hundred nanometres.