Abstract:
An analytical model is developed for laser operation from erbium doped silicon. The
mechanism of erbium excitation through Shockley-Read-Hall (SRH) recombination
process in silicon is analyzed for conditions of achieving the lasing threshold. Stimulated
and spontaneous emission and the stimulated absorption of light by erbium under
different conditions are determined. The effects of erbium concentration, background
doping, erbium lifetime, loss coefficient, cartier lifetime etc. are investigated on the light
output. Enhancement of the absorption coefficient of light with the increase of carrier
injection is studied. Rate equations for the excited erbium atom and photon density are
solved for determining the dynamic characteristics of laser. The steady state values for
excited erbium atom and photon density are determined as a function of the excitation
current. Sinusoidal small signal variation is added to the steady state current density and
modulation transfer function is determined to evaluate the frequency response
characteristics and 3-dB cutoff points. It is found that bandwidth of erbium doped silicon
laser is of the order of hundred MHz range, which increases with the output power level.
Numerical solution of the rate equations for large signal is done for studying the transient
behavior and tum-on time of the laser. The laser tum-on time is found to reduce with the
increasing excitation level.
