=</span> <span class="n">interpolate_material</span><span class="p">(</span><span class="n">TiO2_data</span><span class="p">,</span> <span class="n">frequencies</span><span class="p">)</span>
<span class="n">n_TiO2</span> <span class="o">=</span> <span class="n">n_k_TiO2</span><span class="p">[:,</span> <span class="mi">0</span><span class="p">]</span> <span class="o">+</span> <span class="mi">1</span><span class="n">j</span><span class="o">*</span><span class="n">n_k_TiO2</span><span class="p">[:,</span> <