@article { ISI:000254510300052, title = {Femtosecond dynamics of resonant tunneling and superlattice relaxation in quantum cascade lasers}, journal = {APPLIED PHYSICS LETTERS}, volume = {92}, number = {12}, year = {2008}, month = {MAR 24}, publisher = {AMER INST PHYSICS}, type = {Article}, address = {1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA}, abstract = {Time-resolved mid-infrared pump-probe measurements are performed on a quantum cascade laser below and above the threshold. The gain recovery is determined by the electron transport through the cascade heterostructure. Subpicosecond resonant tunneling injection from the injector ground state into the upper lasing state is found to be incoherent due to the strong dephasing in the active subband. The gain recovery due to transport through superlattice is interpreted in terms of dielectric relaxation within the superlattice miniband. (C) 2008 American Institute of Physics.}, issn = {0003-6951}, doi = {10.1063/1.2898518}, author = {Choi, Hyunyong and Norris, Theodore B. and Gresch, Tobias and Giovannini, Marcella and Faist, Jerome and Diehl, Laurent and Federico Capasso} }