Nonlinear Trapping and Interfering Modes in a Quasi-One-Dimensional Microcavity Laser

Experimental studies of the emission from one-dimensional microcavity laser structure under nonresonant optical excitation are presented. The one-dimensional laser was prepared by electron-beam lithography and reactive ion etching from a planar microcavity sample. Below the lasing threshold, the system was in the strong coupling regime, where the emission exhibits the common exciton-polariton far-field dispersion. Above the threshold, the system switched to the weak coupling regime and the photon lasing was observed. Interestingly, under higher pumping powers above the threshold, a strong blueshift of the lasing mode was observed, with localisation of the far-field emission at finite wavevectors. The near-field images showed interference fringes corresponding to the interference of propagating modes in k-space. This is interpreted in terms of self-interfering modes confined between the pumping spot and the edges of the 1D microlaser.