Evidence for spin memory in photoluminescence of room temperature vertical-cavity quantum dot gain structure

Spin-optoelectronics is a rapidly developing field with promises to provide extra functionalities in communication and spectroscopy via ultrafast polarization modulation [1] . We are addressing the question of spin memory in InAs/GaAs quantum dots (QD) which can serve as gain structures for vertical-external cavity lasers (VECSELs), whereas most previous investigations focused on monolithic VCSELs. VECSELs offer possibilities not only for power scaling but also for additional flexibility as polarization controlling elements can be introduced into the free space sections [2] , [3] . Moreover QDs extend the wavelength coverage of GaAs based materials to the 1300 nm telecomm band with long spin lifetimes having been reported [4] . However, previous investigations concentrated on low temperatures and/or charged/doped dots and we are not aware of results on structures at strong excitation for lasing at room temperature.