Coherence in Y-coupled quantum cascade lasers

A monolithic coupling scheme in which two active waveguides merge into a single waveguide is presented for a GaAs/AlGaAs quantum cascade laser. The evolving fields interfere and a constant phase is observed in the Y-shaped laser cavity, resulting in a far field pattern of a double slit. The mode distribution is comprehensively derived by matching the far field profiles to simulated values and shows a weak current dependence. The device demonstrates the feasibility of coherent laser resonators with prospective applications in interferometric sensing and high power laser arrays. (C) 2007 American Institute of Physics.