Low-crosstalk high-density polymeric integrated optics incorporating self-assembled scattering monolayer.

Highly integrated optical components are strongly demanded because they enable wavelength-division multiplexing optical communication systems to achieve smaller footprints, lower power consumption, and enhanced reliability. Variable optical attenuator (VOA) arrays are often used with optical switches in cascaded form for reconfigurable optical add-drop multiplexer systems. Although VOAs and optical switches based on polymer waveguide technology are commercially available, it is still not viable to integrate these two array devices on a single chip because of significant interchannel crosstalk. In this work, we resolved the issue of crosstalk and integrated the arrays of optical switch and VOA on a single chip by incorporating a self-assembled scattering monolayer (SASM). The SASM was effective for scattering the planar guided mode; consequently, the crosstalk into an adjacent channel was significantly reduced, to less than -35 dB.

FDTD analysis of the light extraction efficiency of OLEDs with a random scattering layer.

The light extraction efficiency of OLEDs with a nano-sized random scattering layer (RSL-OLEDs) was analyzed using the Finite Difference Time Domain (FDTD) method. In contrast to periodic diffraction patterns, the presence of an RSL suppresses the spectral shift with respect to the viewing angle. For FDTD simulation of RSL-OLEDs, a planar light source with a certain spatial and temporal coherence was incorporated, and the light extraction efficiency with respect to the fill factor of the RSL and the absorption coefficient of the material was investigated. The design results were compared to the experimental results of the RSL-OLEDs in order to confirm the usefulness of FDTD in predicting experimental results. According to our FDTD simulations, the light confined within the ITO-organic waveguide was quickly absorbed, and the absorption coefficients of ITO and RSL materials should be reduced in order to obtain significant improvement in the external quantum efficiency (EQE). When the extinction coefficient of ITO was 0.01, the EQE in the RSL-OLED was simulated to be enhanced by a factor of 1.8.

Plastic optical touch panels for large-scale flexible display.

A plastic optical touch panel applicable for large-scale flexible display is demonstrated based on a vertical directional coupling between arrayed channel waveguides and a flexible planar waveguide. When a contact force is applied to the surface, the flexible planar waveguide is bent toward the channel waveguide, and then, the guided mode in the channel waveguide is coupled into the flexible planar waveguide, causing an output power drop. An index-matching liquid is used to fill the gap between the channel and the flexible planar waveguide in order to enhance the transparency of the waveguide touch panel. By applying a force of 1.0 N, the output intensity is decreased by 17 dB, which is sufficiently large for producing a contact signal.

Integrated-optic polarization controllers incorporating polymer waveguide birefringence modulators.

Polarization controllers based on polymer waveguide technology are demonstrated by incorporating thermo-optic birefringence modulators (BMs) and thin-film wave plates. Highly birefringent polymer materials are used to increase the efficiency of birefringence modulation in proportion to the heating power. Thin-film quarter-wave plates are fabricated by using a crosslinkable liquid crystal, reactive mesogen, and inserted between the BMs to produce static phase retardation and polarization coupling. By applying a triangular AC signal to one BM and a DC signal to another, the polarization states of the output light are modulated to cover the entire surface of the Poincaré sphere.

Near-infrared tunable lasers with polymer waveguide Bragg gratings.

Wavelength tunable lasers operating at near infrared (NIR) wavelength are demonstrated through the thermo-optic (TO) refractive index tuning of polymer waveguide Bragg reflectors. The polymer-waveguide device has superior TO efficiency for substantially changing the refractive index, and it enables direct tuning of the Bragg reflection wavelength over a wide range. The waveguide is optimized for NIR wavelengths, and a third-order Bragg reflector is incorporated for facilitating fabrication of the grating. The laser exhibits an output power of 0 dBm, a side-mode suppression ratio of 40 dB, and a tuning range of 21 nm.

Ultra-low inter-channel crosstalk in array waveguide device incorporating self-assembled microsphere diffraction layer.

In array-type optical devices integrated on a single chip with high density, the crosstalk between adjacent devices causes main reason of limited transmission capacity in cascaded optical communication systems. In order to reduce the crosstalk in an arrayed variable optical attenuator, we incorporated a self-assembled monolayer of a microsphere array in the device. The microsphere array introduces a large index contrast in the polymer waveguide, thereby causing strong diffraction of the planar guided modes toward the surface normal directions. Due to the microsphere diffraction, the inter-channel crosstalk between the adjacent channels in a variable optical attenuator array decreases to less than -50 dB.

Polymer waveguide integrated-optic current transducers.

Various functional optical devices are integrated on a single chip in order to construct optical current transducers based on polarization rotated reflection interferometry, which consists of polarization maintaining 3-dB couplers, TE-pass polarizers, TE/TM polarization converters, and thermo-optic phase modulators. By virtue of the device integration, the sensor exhibited good linearity, and excellent accuracy with an error less than 0.2%. The integrated-optic device provides inherent polarization maintaining characteristics and precise controllability of the optical path length in the interferometric sensor. Single chip integration reduces the complexity of the interferometry, and enables mass-production of low-cost high performance current sensors.

Flexible polymer waveguide tunable lasers.

A flexible polymeric Bragg reflector is fabricated for the purpose of demonstrating widely tunable lasers with a compact simple structure. The external feedback of the Bragg reflected light into a superluminescent laser diode produces the lasing of a certain resonance wavelength. The highly elastic polymer device enables the direct tuning of the Bragg wavelength by controlling the imposed strain and provides a much wider tuning range than silica fiber Bragg gratings or thermo-optic tuned polymer devices. Both compressive and tensile strains are applied within the range from -36000 microepsilon to 35000 microepsilon, so as to accomplish the continuous tuning of the Bragg reflection wavelength over a range of up to 100 nm. The external feedback laser with the tunable Bragg reflector exhibits a repetitive wavelength tuning range of 80 nm with a side mode suppression ratio of 35 dB.