An optical amplifier has two amplifying sections formed in a semiconductor structure.
The two amplifying sections have different ratios of gain for two polarization
states (e.g., TE and TM). Thus the amplifier as a whole has a gain ratio determined
by the gains of the two amplifying sections. The two amplifying sections are separately
electronically controllable so as to control the gains of the two amplifying sections
and thus the gain ratio of the amplifier as a whole. Such an amplifier can be made
by quantum well intermixing.
