Design of a C aperture to achieve λ/10 resolution and resonant transmission

Small subwavelength apertures provide high spatial resolution that is not limited by the diffraction limit. However, application of these apertures to practical problems has been hindered by the critical problem of extremely low power transmission efficiency. Recently, we reported a specially designed subwavelength aperture that has a letter C shape (X. Shi, R. L. Thornton, and L. Hesselink, Opt. Lett. 28, 1320 (2003)]. A well-designed C aperture can provide both a high spatial resolution of ~λ/10 and a high power throughput greater than 1. We present the underlying design ideas of the C aperture and report interesting general properties of optical transmissions through a single two-dimensional subwavelength aperture, based on numerical finite-difference time-domain simulations and fundamental observations. These results are expected to provide helpful information for both C-aperture applications and general studies of subwavelength metallic structures.