Measuring the Optical Absorption of Single Nanowires

<p>In this work we present a method to quantitatively measure the optical absorption of single nanowires that can be applied over a wide range of temperatures and with a high enough sensitivity to enable the measurement of below-band-gap absorption (as well as the absorption of single molecules). The method is based on accurately measuring the heat flow coming from a nanowire when it is illuminated by a laser beam. We experimentally verify this method by measuring the absorption of both a zincblende and a wurtzite GaAs, a wurtzite GaP, and a superlattice <span class="MathJax_CHTML mjx-chtml"><span class="mjx-math"><span class="mjx-mrow"><span class="mjx-msub"><span class="mjx-base"><span class="mjx-mi"><span class="MJXc-TeX-main-R mjx-char">Zn</span></span></span><span class="mjx-sub"><span class="mjx-mn"><span class="MJXc-TeX-main-R mjx-char">3</span></span></span></span><span class="MJXc-space1 mjx-msub"><span class="mjx-base"><span class="mjx-mi"><span class="MJXc-TeX-main-R mjx-char">P</span></span></span><span class="mjx-sub"><span class="mjx-mn"><span class="MJXc-TeX-main-R mjx-char">2</span></span></span></span></span></span></span> nanowire. Furthermore, we find that the <span class="MathJax_CHTML mjx-chtml"><span class="mjx-math"><span class="mjx-mrow"><span class="mjx-msub"><span class="mjx-base"><span class="mjx-mi"><span class="MJXc-TeX-main-R mjx-char">Zn</span></span></span><span class="mjx-sub"><span class="mjx-mn"><span class="MJXc-TeX-main-R mjx-char">3</span></span></span></span><span class="MJXc-space1 mjx-msub"><span class="mjx-base"><span class="mjx-mi"><span class="MJXc-TeX-main-R mjx-char">P</span></span></span><span class="mjx-sub"><span class="mjx-mn"><span class="MJXc-TeX-main-R mjx-char">2</span></span></span></span></span></span></span> nanowires have the largest absorption of all these materials. We analyze the advantages and disadvantages of the method and study its range of applicability.</p>