Highly sensitive time-resolved Kerr rotation measurements on single-layer quantum dots

We construct the highly sensitive Kerr rotation system to observe electron spin precession in single-layer quantum dots. The system consists of a photoelastic modulator, a balanced detector and tandem double lock-in amplifiers. The angle resolution achieves 5×10−6 degree, and is highest among the reported so far. To evaluate the possibility of measuring spin relaxation in single-layer quantum dots, we studied the strain-induced GaAs quantum dots. We observe successfully the electron spin precession in the single-layer quantum dots under resonant excitation.