Abstract
All-optical picosecond gate operation is demonstrated using the spin relaxation in a quantum well etalon. Electron spin-polarization photoexcited by circularly polarized light in GaAs quantum wells decays in picoseconds. With the use of the spin relaxation in a quantum well etalon, all-optical full switching is achieved with a decay time of as fast as 7 ps, by adopting a simple optical differential method, which uses only a quarter-wave plate and a polarizer in addition to the conventional all-optical setup. This switching exhibits a contrast between thehigh and the low reflection states of about 10: 7 for a pump pulse energy of 50 fJ/μm2, which is more than 6 times as large as the switching contrast for conventional setup not using the spineffect.
