e air side will radiate predominantly in a narrow cone of angles, associated with the excitation of surface plasmon-polaritons (SPPs) radiating into the glass substrate. By reciprocity, the field enhancement experienced by a dipole near the metal layer is also obtained for a narrow range of angles where conservation of in-plane momentum between the incident light and the SPPs is satisfied.</p>
<div class="sourceCode"><pre class="sourceCode r"><code class="sourceCode r">## from left to right
## incidence air