Abstract
The label-free biosensing technique based on anomalous reflection of gold (AR) is reviewed. The AR method is a phenomenon that a large decrease in reflectivity occurs for blue and purple light upon adsorption of an ultrathin transparent film on a gold surface. This originates from the fact that gold has less metallic character for light with wavelengths shorter than 500 nm. Advantages of AR method for biosensing are (i) the optical setup is simple, (ii) the optical geometry is elastic, (iii) thickness of gold thin films is not limited, and (iv) the method provides us with high spatial resolution compared with conventional surface plasmon resonance imaging. The AR imaging of a protein microarray is also shown to demonstrate the capability of this method.
