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.

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.