Ch. Spiegelberg

Whispering-gallery-mode microring laser using a conjugated polymer

We observed laser emission in whispering gallery modes using a microring composed of a semiconducting polymer poly[2,5-bis-(2′-ethylhexyloxy)-p-phenylenevinylene coated on an etched fiber under transient and quasisteady-state pumping conditions. The threshold for laser oscillation was 1 mJ/cm2 (0.1 MW/cm2) and 30 μJ/cm2 (300 MW/cm2) for nanosecond and femtosecond excitation, respectively. The laser output showed superlinear dependence on the excitation energy above the threshold. The demonstration of lasing under quasisteady-state pumping shows the possibility to develop electrically pumped polymer lasers.

Near diffraction-limited laser emission from a polymer in a high finesse planar cavity

We report near diffraction-limited laser emission from the conjugated polymer BEH:PPV in a cavity made with two dielectric mirrors providing a high finesse planar cavity. The laser has a sharp intensity threshold, a strong directionality, and a high degree of polarization. These emission characteristics are compared with those of a single polymer layer without optical feedback.

Temperature dependence of the threshold for laser emission in polymer microlasers

We studied the temperature dependence of the laser emission threshold in microring polymer lasers. For microring lasers with diameters between 16 and 120 μm, a weak temperature dependence was observed when the temperature was varied between 300 and 10 K. These experimental results are explained within a four-level model. Our results suggest that a significant reduction of threshold can be achieved at low temperatures if the quality factor Q of the microcavities is improved.

Saturation of normal-mode coupling in aluminum-oxide-aperture semiconductor nanocavities

The photon density required for the saturation of normal-mode coupling in oxide-apertured nanocavities is measured to be 90 photons/μm2 by pump-probe experiments. The photon number is only 300 for a semiconductor nanocavity with a 2 μm diameter aluminum-oxide aperture, drastically reduced from 200 000 for a 50 μm waist on a planar microcavity.