Biochemical Signal Detection in Miniaturized Fluidic Systems by Integrated Microresonator

An optical sensor integrated into a polymer microfluidic chip is proposed as a low cost solution to highly parallel biochemical analysis. The sensor consists of a single high-finesse optical resonator for direct analytes detection. High quality silica microspheres (diameter ~300 mum) are easily produced and low-loss whispering gallery modes were excited through evanescent coupling at wavelengths near 1550 nm and 544 nm. The quality factor (Q) and ring down time of these modes is sensitive to minute changes in the microresonator environment thus making it an excellent candidate for a sensor. Instead of the traditional time domain studies, we determine quality factors and ring down times as long as 53.8plusmn0.6 ns (Q~10⁶) from phase shift measurements using optical sources with sinusoidal intensity modulations of 300 kHz and below