Amplitude scaling and lateral shift of leaky radiation from surface plasmon excitation

We investigate spatial field transformation in surface plasmon excitation by a prism coupling configuration. By exciting surface plasmon polaritons (SPPs), the total reflected field is contributed by the direct reflection of the incident wave and the outgoing radiation of the SPP leakage. We show that the SPP leaky radiation field enables both an amplitude scaling and a lateral shift, which play an important role in forming the total reflected field profile. We classify the spatial field transformation by different coupling conditions from weak coupling to critical and strong cases. A method is proposed to evaluate loss rate ratio between the leaky radiation and the material intrinsic absorption, by measuring the reflected beam profile under flat-top beam illumination. This study paves the way for fast computing and optimizing the incident light to control the total reflected field intensity distribution, which is practically significant in the applications of spatial field, such as plasmonic spatial light modulators and computations. (C) 2019 Optical Society of America