1. Field of the Invention
The present invention relates to an optical interrogation/reading system and method for detecting biological substances using one or more grating-based waveguide sensors (e.g., resonant waveguide gratings) that in one embodiment can be incorporated within a microplate.
2. Description of Related Art
Today studies associated with detecting a biological substance (e.g., cell, drug, chemical compound) using resonant waveguide gratings (RWGs) are fast becoming the technology of choice in academia and industry. In such studies, a reading system is used to couple light into the RWG and also used to analyze the light that is reflected from the RWG in order to determine whether or not a biological substance is present on the surface of the RWG. To detect the biological substance, the reading system analyzes the reflected light to locate its resonant wavelength/angle which corresponds to a certain refractive index that is indicative of whether or not the biological substance is located on the surface of the grating-based waveguide sensor. Unfortunately, the reading system used in industry today suffers from a major drawback wherein it is difficult for a user to tune the RWG and reading system so that the reading system can properly interface with the RWG. In particular, it is difficult for a user to tune the RWG so that its resonant wavelength/angle is at a desired spectral location so that the resonant wavelength/angle can be easily detected by the reading system. This drawback is especially troublesome when a multi-channel reading system is used to interface in a multiplexed manner with an array of RWGs. Accordingly, there is a need for a way to make it easier to tune a reading system and RWG to address the aforementioned shortcoming and other shortcomings in the prior art. This need and other needs are satisfied by the reading system, RWG and method of the present invention.
The present invention includes a reading system and at least one grating-based waveguide sensor that interact with one another to enable the detection of biological substances (e.g., cells, drugs, chemical compounds). In one embodiment, the reading system includes a light source (e.g., laser, diode) for directing a light beam into the grating-based waveguide sensor and a detector (e.g., spectrometer, CCD imaging device) for receiving a reflected light beam from the grating-based waveguide sensor and analyzing the reflected light beam so as to detect a resonant wavelength/angle which corresponds to a predetermined refractive index that indicates whether a biological substance is located on the surface of the grating-based waveguide sensor. The grating-based waveguide sensor is tuned to have a resonant wavelength/angle at a predetermined spectral location by adjusting a skew angle defined as an angle between a plane of incidence of the light beam directed into the grating-based waveguide sensor and a grating vector which is perpendicular to the lines of a diffraction grating within the grating-based waveguide sensor. In another embodiment, the reading system is capable of performing a multiplexed interrogation of an array of grating-based waveguide sensors.