By Rolf Haug

The 2008 Spring assembly of the Arbeitskreis Festkörperphysik used to be held in Berlin, Germany, among February 24 and February 29, 2008 together with the 72nd Annual assembly of the Deutsche Physikalische Gesellschaft. The 2008 assembly was once the biggest physics assembly in Europe and one of the greatest physics conferences on this planet in 2008.

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13] found room temperature lasing in a polycrystalline ZnO film deposited by laser ablation on fused silica substrates. Only for pulsed excitation of larger spots they obtained broad spectra at around λ = 388 nm with superimposed sharp lines. The emission patterns looked like distorted rings reminiscent of phase-distorted images of point-like sources. For an explanation the authors argued that only for large enough laser spots some accidentally closed paths along multiple scattering microcrystallites exist.

Since the geometry of the wires was not sufficiently well known, no theoretical modeling and assignment of the modes observed was possible. In polycrystalline laser-MBE grown ZnO films, 50–200 nm thick and consisting of hexagonal pillars with ≈ 50 nm diameter and multiple terraces, Tang et al. [12] found for higher pumping levels at room temperature spectra consisting of sharp, close lying lines in the range of the “P” band. From their spacings, the authors assumed a lateral Fabry-Pérot resonator defined in its length by the size of the stripe-shaped pumping beam to be responsible for the 2 2 mode pattern.

From their spacings, the authors assumed a lateral Fabry-Pérot resonator defined in its length by the size of the stripe-shaped pumping beam to be responsible for the 2 2 mode pattern. 6 μJ/cm ) for this excitonic lasing process was determined, which is about one order of magnitude lower than 42 K. Thonke et al. the values reported for bulk ZnO [4]. Besides the “P” band, at lower energy the “N” band emerged originating from EHP decay for higher pumping levels. Similarly, Cao et al. [13] found room temperature lasing in a polycrystalline ZnO film deposited by laser ablation on fused silica substrates.

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