We present an optofluidic waveguiding lab-on-a-chip used to detect bioparticles. The sensor uses a liquid filled Anti-Resonant Reflecting Optical Waveguide (ARROW) that is interfaced with standard rib waveguides. The rib waveguides are coupled to off-chip lasers and detectors via optical fiber. A perpendicular intersection between the ARROW and a rib waveguide is especially useful for detecting fluorescently tagged particles. Light coupled into the rib waveguide can fluorescently excite these particles within a very small volume. Fluorescent signal can then be guiding within the ARROW and subsequently off chip to a detector.
We will also discuss the details of how our sensor and its different components are fabricated. The ARROW and rib waveguides are made using alternating thin films of tantalum oxide and silicon dioxide on silicon substrates. The various films are deposited by either sputtering or plasma enhanced chemical vapor deposition (PECVD). Both waveguides are patterned using standard photolithographic processes, reactive ion etching, and sacrificial etching. Low-loss optical guiding is very dependent on both the waveguide structure and the materials used. The latest processes for maximizing sensor sensitivity will be reviewed.
We also present results using the optofluidic waveguiding sensor for detecting a variety of different types of particles. Some examples include fluorescently labeled nanobeads, viruses, ribosomes, and RNA.