Silicon photonics is a rapidly emerging field that has allowed optical devices to leverage the massive infrastructure investments made by the semiconductor industry for microprocessor and memory markets. By utilizing the same foundries and processes involved in manufacturing digital electronics, high-volume production of high-quality biosensing devices is possible.
Each biosensor is designed to trap and circulate light from a laser around the perimeter of a device known as a ring-resonator. Each sensor is placed adjacent to a linear waveguide on the chip’s surface that directs light from a laser, past the ring-resonator, and on to a photodetector. As light traverses the linear waveguide each ring-resonator will trap a single wavelength, producing a “notch” in the wavelength spectrum received at the photodetector. The formation of biological complexes on the sensor surface causes the refractive index around the resonator to change, which in turn causes a longer wavelength of light to be trapped and the “notch” to move. The degree of movement of the “notch” is directly proportional to the total mass of bound molecules per unit surface area. During an assay, continuous monitoring of the sensor return spectrum leads to measurement of wavelength shift in resonance peaks, which qualitatively and quantitatively represents reaction dynamics.