Direct electronic compensation of the amplification nonlinearity in semiconductor laser amplifiers

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Abstract
Direct electronic compensation of the inherent amplification nonlinearity of semiconductor laser amplifiers is investigated. It is found that operating the active layer junction from a voltage source, which in theory would hold the carrier density at a constant value, does not remove the amplification nonlinearity because of the intraband carrier dynamics. However, compensation of the nonlinearity is shown to be possible by driving the laser amplifier from a negative output impedance source. Using this at 80 mA drive current compensation of the amplification nonlinearity is demonstrated for a 1310 nm polarization insensitive multiple quantum well laser amplifier showing 18 dB gain (13 dB fiber to fiber) and a nonlinearity of 0.36 dB/mW. It is further shown that the intraband carrier dynamics, mainly the carrier heating, cause limitations to both the driving conditions for which the nonlinearity can be compensated, and to the use of laser amplifiers as an amplifying detector.