Abstract

The optimum number of quantum wells in a phase/absorption modulator or a laser device depends upon the device design, where more wells and the corresponding larger confinement factor can be offset by other factors. Strong tunable quantum size effects have been predicted and observed in waveguide phase and absorption modulators[1-3], and studied as a function of wavelength and voltage near the band edge[4-5] but the optimum number of wells remains uncertain. At one extreme would be a device with no quantum wells at all and using the bulk linear electro-optic (LEO) effect, which would exhibit a chirp parameter nearly infinite (ideal phase modulation). At the other extreme would be a device filled with wells where quantum effects would dominate and the chirp parameter can be <<1 (ideal absorption modulation). An optimum number of wells for a device integrated with a laser may be between these extremes, where the chirp parameter is >10 and there are enough wells to provide a strong effect but not too many to prevent lasing in the active section. This paper compares experimental results to expected values for three structures each with different numbers of wells and compares the advantages of each case.

© 1989 Optical Society of America