Biosensing using surface electromagnetic waves in photonic band gap multilayers

A biosensor based on the excitation of surface electromagnetic waves in photonic band gap multilayer films is demonstrated. The operating principle of this device is similar to surface plasmon biosensors with the key difference that a photonic band gap film replaces the metal film as the medium in which surface electromagnetic waves are excited. The use of photonic band gap films offers a number of advantages. First, the surface wave resonance is much sharper leading to the potential of greatly enhanced sensitivity. Second, the properties of the photonic band gap material can be engineered to make a sensor that operates at any wavelength. The experiments reported here are conducted with a surface wave resonance at 470 nm, a wavelength not generally accessible with surface plasmon sensing. Finally, the photonic band gap films are more mechanically robust than metal films and they offer new substrates for surface chemistry. The paper describes the design of the photonic band gap films, the surface chemistry and biology to create sensing chips, and the spectroscopic experimental configuration used to observe and track the surface mode resonance. Experimental results are presented on refractive index sensing, antibody–antigen reactions, and DNA binding.