Optical losses and efficiency in GaAs laser diodes

Optical gain and losses of GaAs laser diodes were deduced from the length dependence of the threshold current density and the differential external quantum efficiency at 77 and 300°K. It has been confirmed that the optical gain is proportional to the threshold current density J
t
; and the optical losses are given by the sum of current independent term
\alpha_{0}'
, and current dependent term
\beta"J_{t}
, which is proportional to the threshold current density. The term
\beta"J_{t}
depends on the laser wavelength because the threshold current density depends on the laser wavelength. It is believed that
\beta"J_{t}
is caused by the penetration of the laser oscillations into the noninverted regions surrounding the inverted population region of the
p-n
junction.