Temperature-activated polarization of single photon emitters

Abstract

Controlled activation of the polarization of single photon emitters is a challenge. We use CdSe/CdS dot-in-rods (DRs) confined and oriented in smectic topological grain boundaries to activate the fluorescence polarization through temperature variation. We show that temperature acts as a knob to switch on/off the polarization of DR emitted light between smectic and isotropic phase. This occurs through the orientational motion of the DR assemblies, which is induced in isotropic phase due to the disappearing of the defects. In addition, we evidence a significant improvement of DR emitted light polarization after cooling back from the isotropic phase. It is measured by the increase in polarization degree from 0.28 to 0.36 on average for DR assemblies. This improvement is managed by the smectic phase diagram near the smectic/nematic transition. Near the smectic/nematic transition, the smectic grain boundaries entirely cover the sample surface and allow for a reorientation of all DRs, even of those initially not confined in smectic grain boundaries.