Tailoring the refractive index of nanoimprint resist by blending with TiO_2 nanoparticles

Abstract

We demonstrate that blending of TiO2 nanoparticles into nanoimprint polymer resist yields a composite material with an increased optical refractive index suitable for nanoimprint lithography. Complex refractive indices of n400nm = 1.94-i0.009, n500nm = 1.86-i0.003, and n600nm = 1.83-i0.002 are predicted for composite materials with 30% TiO2 nanoparticles of 35-nm diameter in Amonil UV nanoimprint resist. Layers with concentrations of 1 to 30 volume% of TiO2 nanoparticles blended into the composite resist material are prepared by spin-coating. Good agreement between measured and predicted optical properties is obtained. Using the composite imprint resist periodic linear gratings with periods of 370 nm are fabricated on glass substrates using UV nanoimprint lithography. Subsequently, an organic light emitting diode (OLED) is fabricated on top of the grating. Due to the high-index grating structure, waveguide modes are extracted from the OLED, which are observed in the OLED emission spectrum.