The authors investigate carrier dynamics in a passive InAs/InP quantum dot (QD) waveguide using 255 fs optical pulses at a central wavelength of 1568 nm. We observe strong anisotropy of absorption saturation for different polarizations. Pump–probe measurements indicate the presence of carrier relaxation dynamics on a timescale in the order of tens of picoseconds due to cascaded relaxation of carriers generated by two-photon absorption (TPA) from the bulk region to the QDs via the wetting layer. These relaxation timescales are much longer than in QD amplifiers. Our observations are supported by a rate-equation model which includes TPA, showing good agreement with the pump–probe measurements.
Ju, H., Molina Vázquez, J., Li, Z., Nötzel, R., Vries, de, T., Lenstra, D., Gong, Q., Veldhoven, van, P. J., Wolter, J. H., Khoe, G. D., & Dorren, H. J. S. (2006). Polarization-dependent carrier dynamics in a passive InAs/InP quantum dot waveguide. Optics Communications, 259(2), 861-867. https://doi.org/10.1016/j.optcom.2005.09.058