Gain, frequency bandwidth, and saturation output power of AlGaAs DH laser amplifiers

Signal gain, frequency bandwidth, and saturation output power, which are important parameters in determining preamplifier and linear repeater system performance, are studied theoretically and experimentally for AlGaAs Fabry-Perot cavity type laser amplifiers. Multimode rate equations with an input signal term are solved for the exponential bandtail model with no -selection rule. Experimental results are in reasonable agreement with theoretical predictions. The maximum signal gain, frequency bandwidth, and the tolerance of the optical center frequency control are determined by facet mirror reflectivity and cavity length. The unsaturated signal gain increases with the pumping rate and the maximum signal gain as high as 21-28 dB is obtained near oscillation threshold for various cavity structures. The frequency bandwidth, at which signal gain is decreased by 3 dB from the low frequency value, is 1 GHz at 21 dB signal gain for a 900μm cavity length amplifier. The saturation output power, at which the signal gain is decreased by 3 dB from the unsaturated value, is -10 to -5 dBm. The saturation output power will be improved by 18 dB in a traveling wave type amplifier.