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HL: Fachverband Halbleiterphysik

HL 97: Semiconductor laser II: Microcavities and quantum-dot laser

HL 97.1: Vortrag

Donnerstag, 3. April 2014, 15:30–15:45, POT 051

Direct Net Gain Measurements in Organic Microcavities — •Christian Tzschaschel, Markas Sudzius, Andreas Mischok, Hartmut Fröb, and Karl Leo — Institut für Angewandte Photophysik, Technische Universität Dresden, Georg-Bähr Str. 1, 01069 Dresden

A profound knowledge of absorption and net gain coefficients of the active material is crucial for designing microcavity lasers. An extremely high degree of optical confinement in such systems modifies the spontaneous emission properties of the gain medium. Standard gain measurement techniques, such as the variable stripe length method, are thus rendered unreliable and hardly applicable.

In this work, a novel technique is presented. It allows direct measurements of both net gain and absorption coefficients of optically pumped organic microcavities. The method involves an in-depth analysis of the line shape of the cavity mode, which is then compared to transfer-matrix simulations. The use of wedge-shaped cavities provides tunable devices and allows for a detailed analysis of spectral net gain properties. The method is applied to organic microcavity structures consisting of a highly fluorescent laser dye (DCM), doped into a matrix material (Alq₃) and sandwiched between distributed Bragg reflectors. For this system, gain coefficients as high as 750 cm⁻¹ have been extracted at optical pumping close to the lasing threshold.