High performance planar microcavity organic semiconductor lasers based on thermally evaporated top distributed Bragg reflector

Abstract

High performance organic semiconductor lasers (OSLs), especially those under current injection, have been sought for decades due to their potentially great applications in fields such as spectroscopy, displays, medical devices, and optical interconnection. The design and fabrication of high-quality resonators is a prerequisite for high performance OSLs. In the case of planar microcavities, the fabrication process of top distributed Bragg reflectors (DBRs) usually requires electron beam evaporation or manual lamination on top of organic thin-film layers, which can lead to issues including degradation of the organic materials, large-scale non-uniformity, and difficulties for current injection. Here, we report a non-destructive way of fabricating a top DBR by thermal evaporation. The top DBR based on thermally evaporated alternative TeOx/LiF stacks shows low morphological roughness, high process tolerance, and high reflectivity. Moreover, the deposition process causes negligible damage to the organic thin-film layers underneath. With the combination of a conventional e-beam evaporated bottom DBR, a high performance planar microcavity OSL with a low threshold of 1.7 μJ cm-2, an emission linewidth of 0.24 nm, and an angular divergence of <3° has been achieved under nitrogen laser pumping. Similar performance, with a high Gaussian beam quality comparable with that of an ideal diffraction-limited beam, was also obtained under diode pumping, showing the potential of this technique for building compact and cost-effective organic lasers with good beam quality. Our result will open a promising route for future high performance microcavity optoelectronic devices, especially for laser devices under current injection.