Subhertz spectral fluctuations from high-density excitons in coupled quantum wells

In 1994 Butov ct al. [Phys. Rev. Lett. 73, 304 (1994)] reported large, extremely low-frequency fluctuations in the luminescence intensity from indirect excitons in a coupled quantum well. Sire have reproduced these fluctuations in a similar structure. Our observations indicate, however, that, the fluctuations are spectral fluctuations rather than intensity fluctuations. We have eliminated several possible causes for the fluctuations and propose a possible cause. (C) 2000 Optical Society of America. OCIS codes: 300.6280, 300.6470, 190.3100, 190.4720, 190.5970, 270.1670.