Semiconductor microlasers with intracavity microfluidics for biomedical analyses

摘要

Recently demonstrated microfluidic chips have the potential to be useful bioanalytical tools for DNA, protein, and cellular studies. To realize this potential, means for introducing fluids, separating their components, and detection must be integrated onto the chip. The authors have investigated semiconductor laser microcavity spectroscopy as a means for ultrasensitive detection of various fluids, cells, and particulates. Two methods for implementing this laser device are illustrated. A scanning method for reading the light signals from a static fluid in the microcavity is presented. The device has a microfabricated flow structure formed between two surfaces, a vertical cavity surface-emitting laser and a glass dielectric mirror. The resonance frequencies of this Fabry-Perot microcavity are very sensitive to the dielectric properties of the fluids confined inside the cavity. Further, the resonance linewidth or cavity Q is sensitive to the optical length of the cavity, light absorption, and light scattering from the fluid and the surfaces forming the cavity. If cells or particulates are present in the fluid they confine light transverse to the cavity length and develop additional sub-frequencies between the Fabry-Perot frequencies. Thus, the spectrum of light emitted from or transmitted through the cavity comprises a wealth of information about the cavity contents.