Polycrystalline ZnO Films and Random Lasers

The frequencies of the sharp peaks depended on the sample position, when the excitation spot was moved across the film, the frequencies of the sharp peaks changed. Above the threshold, the integrated emission intensity increased much more rapidly with the pump power, and the emission was measured to be strongly polarized indicating that laser action has occurred in the ZnO films. 

The microlasers have potential applications in integrated photonic circuits. The demonstration of random lasers opens up the possibility of using disordered semiconductor microstructures as alternative sources of coherent light emission. 

The fabrication of the conventional microlasers requires expensive state-of-the-art crystal growth and microfabrication facilities. The realization of lasing in semiconductor polycrystalline films, which are nonepitaxially grown on amorphous fused silica substrates, provides a possibility to fabricate semiconductor lasers on many different types of substrates. As a result, fabrication of such a polycrystalline film-based microlaser is much easier and less expensive than that of most microlasers. In this context, development of methods for growing high-quality polycrystalline ZnO films is important, because polycrystalline ZnO films also have many other applications as phosphors, coatings, and so on in various devices [166]. 

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