Optical waveguides for on-chip fluorescence measurements (Conference Presentation)

Optical waveguides using a visible transparent nitride were developed to perform fluorescence measurement on a chip. Through finite difference time domain (FDTD) design, the exciting green light was guided by the micron-scale ridge waveguide, while its evanescent wave was expanded outside the waveguide surface and capable to efficiently excite the fluorescent molecules that were approaching the waveguide facets. Since the waveguide was centimeters long, it has a longer fluorescence excitation path comparing to traditional samples prepared for microscopy measurements. As result, the waveguide device can excite stronger fluorescent signals. In addition, the nitride waveguide was prepared by the complementary metal–oxide–semiconductor (CMOS) process thus enabling high volume manufacturing and reducing the cost of the device fabrication. The AlN waveguide was then integrated with a microfluidic devices to experimentally demonstrate real-time fluorescence detection. Solution samples with different dye concentrations were sequentially injected into the microfluidic chamber. By recording the emission signals, we showed that the fluorescent signals were consistently amplified as the dye concentrations increased. In addition, real-time fluorescence detection with a response time less than seconds was achieved. The developed waveguide based fluorescence measurement provides a new miniaturized platform for low cost and highly accurate point-of-care application.