Small-signal modulation of a two-section semiconductor laser amplifier: Pure PM response

A description is given of how a near-traveling-wave two-section semiconductor laser amplifier used as an external modulator can accomplish phase modulation (PM) without any accompanying amplitude modulation (AM). The analysis, performed by numerical small-signal simulation, shows that it is possible to obtain pure PM by adjustment of the ratio of the modulation currents of the two sections. An AM-suppressed PM response of 0.4 pi rad/mA with a 3-dB modulation bandwidth, of 1 GHz can be obtained.<
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