Coherence characteristics of electrically excited tandem organic light-emitting diodes.

A tandem organic light-emitting diode structure, excited electrically in the pulsed domain and confined within a double spatial filter configuration, is observed to emit a low-divergence beam (deltatheta approximately 2.53 mrad, or approximately 1.1 times the diffraction limit) with a near-Gaussian spatial distribution. The emission originates from the laser dye Coumarin 545 T, which is used as a dopant. Spectral coherence was determined by use of a double-slit interferometer. The interferometric distribution from our device approximates the interferometric pattern obtained from well-known lasers emitting at lambda approximately 540 nm.