title: Coherent coupling of multiple transverse modes in quantum cascade lasers.
abstract: Quantum cascade lasers are a unique laboratory for studying nonlinear laser dynamics because of their high intracavity intensity, strong intersubband optical nonlinearity, and an unusual combination of relaxation time scales. Here we investigate the nonlinear coupling between the transverse modes of quantum cascade lasers. We present evidence for stable phase coherence of multiple transverse modes over a large range of injection currents. We explain the phase coherence by a four-wave mixing interaction originating from the strong optical nonlinearity of the gain transition. The phase-locking conditions predicted by theory are supported by spectral data and both near- and far-field mode measurements.
authors.affiliation: School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Nanfang
authors.initials: N
authors.lastname: Yu
authors.forename: Laurent
authors.initials: L
authors.lastname: Diehl
authors.forename: Ertugrul
authors.initials: E
authors.lastname: Cubukcu
authors.forename: David
authors.initials: D
authors.lastname: Bour
authors.forename: Scott
authors.initials: S
authors.lastname: Corzine
authors.forename: Gloria
authors.initials: G
authors.lastname: Höfler
authors.forename: Aleksander K
authors.initials: AK
authors.lastname: Wojcik
authors.forename: Kenneth B
authors.initials: KB
authors.lastname: Crozier
authors.forename: Alexey
authors.initials: A
authors.lastname: Belyanin
authors.forename: Federico
authors.initials: F
authors.lastname: Capasso