Linewidth determination from electrical noise measurements on semiconductor lasers

A novel method to determine the linewidth of a semiconductor laser is described. By measuring the noise voltage at the electrical terminal, the electron density variations in the gain medium can be determined. Since these variations are the major cause of the linewidth of semiconductor lasers, both the linewidth and the lineshape can be determined from electrical measurements if the ¿-parameter is known and the parasitic impedances of the laser are small.