The amplified-spontaneous-emission spectrum of the light field in the nonlasing supermode of two coupled semiconductor lasers is analyzed with linearized Langevin equations. It is shown that the interference between the laser mode and the fluctuating light field in the nonlasing mode causes spatial hole burning. This effect introduces a phase-sensitive coupling between the laser field and the fluctuations of the nonlasing mode. For high laser fields this coupling splits the spectrum of the nonlasing mode into a triplet consisting of two relaxation oscillation sidebands that are in phase with the laser light and a centerline at the lasing frequency with a phase shift of ±π/2 relative to the laser light. As the laser intensity is increased close to threshold, the spectrum shows a continuous transition from the single amplified-spontaneous-emission line at the frequency of the nonlasing mode to the triplet structure. An analytical expression for this transition is derived, and typical features are discussed.
© 1999 Optical Society of America
Holger F. Hofmann and Ortwin Hess, "Spatial hole-burning effects in the amplified-spontaneous-emission spectrum of the nonlasing supermode in semiconductor laser arrays," J. Opt. Soc. Am. B 16, 137-146 (1999)