DIRECT ELECTRONIC COMPENSATION OF THE AMPLIFICATION NONLINEARITY IN SEMICONDUCTOR-LASER AMPLIFIERS

Direct electronic compensation of the inherent amplification nonlinear ity of semiconductor laser amplifiers is investigated. It is found tha t operating the active layer junction from a voltage source, which in theory would hold the carrier density at a constant value, does not re move the amplification nonlinearity because of the intraband carrier d ynamics. However, compensation of the nonlinearity is shown to be poss ible by driving the laser amplifier from a negative output impedance s ource. Using this at 80 mA drive current compensation of the amplifica tion nonlinearity is demonstrated for a 1310 nm polarization insensiti ve multiple quantum well laser amplifier showing 18 dB gain (13 dB fib er to fiber) and a nonlinearity of 0.36 dB/mW. It is further shown tha t the intraband carrier dynamics, mainly the carrier heating, cause li mitations to both the driving conditions for which the nonlinearity ca n be compensated, and to the use of laser amplifiers as an amplifying detector.