> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">vstack</span><span class="p">([</span><span class="n">d_air</span><span class="p">,</span> <span class="n">d_TiO2</span><span class="p">,</span> <span class="n">d_Ag</span><span class="p">,</span> <span class="n">d_TiO2</span><span class="p">,</span> <span class="n">d_air</span><span class="p">])</span>  <span class="c1"># No frequency dependence on thickness</span>

<span class="c1"># Calculate R and T over the freq