The output spectrum of an external cavity semiconductor laser (ECLD) has been deduced, based on the fact that the laser radiation is developed from the amplified spontaneous emission generated inside the diode itself. An explicit analytical expression is derived for the threshold carrier density when the ECLD is tuned to oscillate at arbitrary wavelength. It is shown that the combination of the spectrum and the carrier rate equation can provide self-consistent predictions to the characteristics of the ECLD. For example, applying the photon density of the oscillation ECLD mode obtained from the expression of the spectrum to the carrier rate equation, the carrier deficit from the threshold density and output power of the tunable ECLD can be determined.
展开▼
