Angle-dependent resonance of localized and propagating surface plasmons in microhole arrays for enhanced biosensing

Abstract : The presence of microhole arrays in thin Au films is suited for the excitation of localized and propagating surface plasmon (SP) modes. Conditions can be established to excite a resonance between the localized and propagating SP modes, which further enhanced the local electromagnetic (EM) field. The co-excitation of localized and propagating SP modes depends on the angle of incidence (θexc) and refractive index of the solution interrogated. As a consequence of the enhanced EM field, enhanced sensitivity and an improved response for binding events by about a factor of 3 to 5 was observed with SPR sensors in the Kretschmann configuration for a set of experimental conditions (λSPR, θexc, and η). Thus, microhole arrays can improve sensing applications of SPR based on classical prism-based instrumentation and are suited for SP-coupled spectroscopic techniques.