Intense switchable fluorescence in light wave coupled electrowetting devices

Switchable fluorescence has been obtained from light wave coupled (LWC) electrowetting (EW) devices fabricated on an optical waveguide substrate. The LWC device structure contains a polar water component and a nonpolar oil component that compete for placement on a hydrophobic surface under the influence of an applied electric field. The oil film contains organic lumophores that fluoresce intense red (608 nm), green (503 nm), and blue (433 nm) light with similar to90% quantum efficiency when excited by violet light. Violet InGaN light-emitting diodes (LEDs) couple similar to405 nm excitation light into the waveguide substrate. EW of the water layer displaces the fluorescent oil film such that it is either optically coupled to, or decoupled from, the underlying waveguide. The output luminance can be modulated from >100 cd/m(2) to <5 cd/m(2) as a dc voltage ranging from 0 to -24 V is applied to the water layer. Maximum luminance of 15x30 arrays of the devices may exceed similar to500 cd/m(2) by simply increasing the output of the InGaN LEDs. (C) 2005 American Institute of Physics.