Multimode interference devices for focusing in microfluidic channels

Abstract

Low-cost, compact, automated optical microsystems for chemical analysis, such as microflow cytometers for identification of individual biological cells, require monolithically integrated microlenses for focusing in microfluidic channels, to enable high-resolution scattering and fluorescence measurements. The multimode interference device (MMI), which makes use of self-imaging in multimode waveguides, is shown to be a simple and effective alternative to the microlens for microflow cytometry. The MMIs have been designed, realized, and integrated with microfluidic channels in a silica-based glass waveguide material system. Focal spot sizes of $2.4\mathrm{\mu m}$ for MMIs have been measured at foci as far as $43.7\mathrm{\mu m}$ into the microfluidic channel.

© 2011 Optical Society of America