Ultrafast carrier dynamics and resonant inter-miniband nonlinearity of a cubic GaN/AlN superlattice

Abstract

We investigate the linear and dynamical nonlinear optical properties of a superlattice composed of ultra-narrow n-doped GaN/AlN quantum wells. Owing to huge band offsets, the structures feature a broad inter-miniband transition in the telecom window at 1.55 μm. Resonant pump-probe experiments directly reveal ultrafast intersubband relaxation occurring within <100 fs. We estimate an associated third order nonlinear optical susceptibility of Im(χ(3))∼1.1×10−20 m2/V2. The polarization and angular dependences of the optical response confirm the nonlinearity as originating from inter-miniband transitions in the heterostructure.