Effect of silver nanoisland-embedded grating for surface plasmon based total internal reflection fluorescence imaging

We present the enhancement of total internal reflection fluorescence microscopy by the excitation of localized surface plasmons using nanoisland embedded subwavelength grating. The presence of nanoislands may provide additional field enhancement even at moderate grating period. For fabrication of nanoisland embedded grating patterns, a silver film was first evaporated on a glass substrate. Next, silver grating was patterned by e-beam lithography. Subsequently, nanoisland shapes were chemically formed. Field enhancement was measured by fluorescent excitation of microbeads on periodic silver nanoislands. The performance is compared to the microbead excitation on a silver nanograting without nanoislands and nanoislands formed on a thin film without grating patterns as controls. The result confirms additional field enhancement by nanoisland embedded periodic patterns.