Low-temperature Near-field Scanning Optical Microscope for UV-visible Spectroscopy of Nanostructures

A low-temperature near-field scanning optical microscope (LT-NSOM) is designed and realized in order to study the optical properties of nanostructures at cryogenic temperatures in the UV-visible wavelength range. Due to the simple and extensive optical design, any type of NSOM operation mode is accessible. In particular, the localized photoluminescence spectra of nanostructures can be measured at temperatures from 13 K up to 300 K. We successfully demonstrate the performance of our LT-NSOM by investigating InGaN/GaN multiple quantum wells grown on a sapphire substrate at 15 K.