The effects of spatial correlation on the linewidth broadening in tunable laser diodes

Spectral linewidth broadening by carrier density fluctuations in electronically wavelength-tunable diodes is analyzed, taking into account the spatial correlation of the fluctuations. The correlation over the entire cavity length occurs via currents flowing longitudinally along the metal contacts and links together spatially independent potential fluctuations associated with the carrier density fluctuations. At small tuning currents, an almost complete correlation occurs, while at large tuning currents, the uncorrelated-fluctuations approximation is asymptotically approached. A broadening mechanism in tunable laser diodes due to finite cladding layer resistance is discovered