Comparison of effective /spl alpha/-parameters for semiconductor Mach-Zehnder optical modulators

The small-signal /spl alpha/-parameter of a semiconductor Mach-Zehnder modulator depends on the device design and on the bias and modulation voltages applied to the two independent drive electrodes. In particular, for the range of applied voltages which correspond to switching the modulator from the off state to the on state, the /spl alpha/-parameter varies significantly. Effective, large-signal /spl alpha/-parameters provide a convenient and concise description of the modulator chirp. For a multiple quantum well Mach-Zehnder modulator, a comparison is made between four effective /spl alpha/-parameters; a transmission performance /spl alpha/-parameter, an on/off /spl alpha/-parameter, a 3 dB /spl alpha/-parameter and a chirp /spl alpha/-parameter. Both conventional and phase-shifted modulators are considered.