Funktionale Grenzflächen

Raman scattering spectroscopy allows the direct and fast study of molecules by analysis of their vibrational normal modes. However, for certain materials the scattered signal is superimposed by fluorescence, which – if present – overwhelms the intrinsically weak Raman signal by orders of magnitude. An approved method to resolve the instantaneous Raman signal of interest from the delayed fluorescence background is time-correlated single-photon counting (TCSPC). For that, a single-photon detector with fast dynamics is required. The, so-called, superconducting nanowire single-photon detector (SNSPD) is a promising candidate for TCSPC. We have developed an optical instrument using such a SNSPD for the TCSPC method. The detector is made from a 5 nm thick NbN film, patterned by electron-beam lithography in a meander line with a width of 100 nm and a filling-factor of 50 %, covering an active area of 4 × 4 µm². As a proof of concept we have shown that it is possible to resolve low power optical signals ( between 520 and 630 nm) with a timing jitter of about 35 ps. Based on our experimental results we will discuss perspectives and limits of SNSPD application for spectroscopy.