Polarization properties of solid-state organic lasers

Abstract

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.

Spectra, thresholds, and modal fields of a kite-shaped microcavity laser

“…The other peaks should correspond to quasi-WG modes, since their optical length is close to the perimeter. Moreover the identification of these two types of modes is reinforced by the analysis of the polarization states of their emission [45]. Actually, the FP-like mode was shown to be polarized mainly within the cavity plane, while WG-like modes exhibited prevalence for a polarization orthogonal to the cavity plane.…”

Gain properties of dye-doped polymer thin films

“…Absorption and emission of light in organic semiconductors are known to be strongly polarization-dependant [33,34,45]. For instance, pump polarization can modify ASE intensity and laser threshold up to a factor of three.…”

“…Due to the molecular structure of organic materials, amplification is in general anisotropic in such media [45]. In an approximate model, dye molecules in a polymer matrix can be considered as fixed and non-interacting dipoles.…”

“…For the propagating laser field, we use the model of the effective index described in [32], and consider the first vertical excitation with TE polarization, which means that the electric field lies in the plane of the layer. Actually, for ASE and Fabry-Perot microlasers, the laser emission is mostly TE polarized [45]. The confinement factor was numerically estimated based on Eq.…”

Microcavity lasers on polymer materials: Boundary integral equation modeling and experiments

“…Experiments were performed on kite-shaped dye-doped polymer microlasers [17,40,41]. Planar dimensions of such microlasers were from 100 to 200 μm that was several orders of magnitude larger than both the cavity thickness of 0.5 μm and the emission wavelength of 0.6 μm.…”