Self-Mode-Locking of Quantum Cascade Lasers with Giant Ultrafast Optical Nonlinearities
Roberto Paiella,1*
Federico Capasso,1
Claire Gmachl,1
Deborah L. Sivco,1
James N. Baillargeon,1
Albert L. Hutchinson,1
Alfred Y. Cho,1
H.
C. Liu2
We report on the generation of picosecond self-mode-locked pulses
from midinfrared quantum cascade lasers, at wavelengths within the
important molecular fingerprint region. These devices are based on
intersubband electron transitions in semiconductor nanostructures,
which are characterized by some of the largest optical nonlinearities
observed in nature and by picosecond relaxation lifetimes. Our results
are interpreted with a model in which one of these nonlinearities, the
intensity-dependent refractive index of the lasing transition, creates
a nonlinear waveguide where the optical losses decrease with increasing
intensity. This favors the generation of ultrashort pulses, because of
their larger instantaneous intensity relative to continuous-wave
emission.
1 Bell Laboratories, Lucent Technologies, 600 Mountain Avenue, Murray Hill, NJ 07974, USA.
2 Institute for Microstructural Sciences, National
Research Council, Ottawa, Ontario, K1A 0R6, Canada.
*
To whom correspondence should be addressed. E-mail:
robertop{at}lucent.com
