The polarization states of lasers are crucial issues both for practical applications and fundamental research. In general, they depend in a combined manner on the properties of the gain material and on the structure of the electromagnetic modes. In this paper, we address this issue in the case of solid-state organic lasers, a technology which enables to vary independently gain and mode properties. Different kinds of resonators are investigated: in-plane micro-resonators with FabryPerot, square, pentagon, stadium, disk, and kite shapes, and external vertical resonators. The degree of polarization P is measured in each case. It is shown that although TE modes prevail generally (P >0), kite-shaped micro-laser generates negative values for P , i.e. a flip of the dominant polarization which becomes mostly TM polarized. In general, we demonstrate that both the pump polarization and the resonator geometry can be used to tailor the polarization of organic lasers. With this aim in view, we, at last, investigate two other degrees of freedom, namely upon using resonant energy transfer (RET) and upon pumping the laser dye to a higher excited state. We then demonstrate that significantly lower P factors can be obtained.

The far-field pattern of stadium-shaped organic microlasers is strongly modified by introducing circular air vacancies within the cavity, so as to control it in a predictive way. Experimental results are in good agreement with geometrical optics predictions whereas spectral properties of emission are investigated to improve the understanding of the lasing modes.