Lecture: Two- and Three-dimensional organic microlasers

08.11.2017, 11:30

Dr. Stefan Bittner, Department of Applied Physics, Yale University, New Haven, CT 06511, USA

Place: 
MPL, Seminar Room A1.500, MPL, Staudtstr. 2, 91058 Erlangen

Abstract

Microlasers have been intensively investigated in view of applications like biological and chemical sensing, coherent on-chip light sources or speckle-free illumination. The key parameter deter- mining their spectral and emission characteristics is their shape, and hence understanding the relations between geometry and lasing modes is of great importance. The central paradigm for this is semiclassical physics which studies the connections between wave physics (wave optics) and classical mechanics (ray optics). Indeed, many properties of microlasers can be explained by the ray dynamics of their cavities, and ray optics can even be used to design microlasers with specific properties. Several examples of organic microlasers are presented and how their lasing modes are related to classical ray trajectories, in particular periodic orbits.

While azimuthally symmetric resonators permit ultra-high quality factors, they are not useful as light sources since they emit uniformly in all directions. It has, however, been shown that deformed cavities with chaotic ray dynamics can exhibit highly directional emission while retaining good quality factors. One example is the so-called short-egg cavity [See Fig. 1(a)], and unidirectional emission has been demonstrated with organic microlasers of this shape [1].

Another interesting class of cavity shapes are polygons, which play a role both as microlasers and in electromagnetic scattering problems like radar applications. It was found that the lasing spectra and field distributions of triangular microlasers are strongly connected to classical periodic orbits and to diffraction at the cavity corners [2].

Finally, three-dimensional organic microlasers are discussed. While most work on microlasers and optical microcavities is based on flat, effectively two-dimensional structures, three-dimen- sional cavities bear the potential for new functionalities in view of applications. First results with cuboid microlasers [see Fig. 1(b)+(c)] are presented. Furthermore, potential applications as, e.g., sensors or spectrometers along with fundamental questions regarding their polarization states and the ray-wave correspondence in these systems are discussed.

Figure 1: (a) Far-field intensity distribution of an organic microlaser with the “shortegg” shape [1]. (b) Scanning-electron micrograph of a cuboid microlaser and (c) an image of a lasing cuboid (lasing emission in yellow, scattered pump light in green) [3].

[1] Schermer et al., 106, 101107 (2015).

[2] Lafargue et al., PRE 90, 052922 (2014).

[3] Chen et al., Opt. Express 22, 12316 (2014).