Analysis of diode laser properties - Part II

Using an exponential approximation to the band-to-band absorption of a GaAs active region in the vicinity of the lasing photon energy, a simple model for the medium gain varying with pumping is formulated. Based on that model, many laser properties are determined analytically as functions of the device parameters. Below threshold the spectral gain and power peaks are calculated. These shift with pumping and coalesce at threshold. Threshold current is expressed in terms of laser dimensions and other descriptors, as is lasing wavelength. Depending on the active region gain versus photon energy relation, threshold current may continue to decrease with active region thickness until the domain of quantum-well effects is attained. We derive formulas relating spectral envelope width and output power. These quantities vary inversely near and above threshold. Spectral envelope asymmetry is also calculated and is shown to decrease rapidly with output power.