Construction of a liquid He cryostat insert for high spatial resolution photoluminescence experiments on GaAs

Abstract

A high-spatial resolution focusing and translation mechanism for photoluminescence experiments at 4.2 K on GaAs is demonstrated. The restrictions posed on the obtainable spatial resolution of conventional setups, where the focusing lenses are situated outside a liquid He cryostat, were circumvented by building the microscope objective and the translation stage into the cryostat. The objective and the translation stage are functioning at 4.2 K and are controlled from outside the cryostat. A spatial resolution of 1 μm was obtained. Up to eight crystals can be mounted and interchanged during an experiment without returning to room temperature. A horizontal translation table was constructed based on two separate spring systems for each direction of translation. Thermal leakages were minimized so that a hold time of 20 h for a conventional liquid-He-bath cryostat was reached.