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Lasing mode regulation in zinc oxide microcavity

As a short-wave optoelectronic device, ultraviolet (UV) nano laser has a broad prospect in the fields of electronics, information, communication, environmental monitoring and biomedical testing. Zinc oxide (ZnO) microcavities show significant advantages in the realization of UV laser with low threshold and high quality factor. Resonance mode regulation and single-mode realization are the key problems for the practical application in ZnO microcavity UV laser. Based on the basic theory of microcavity mode, this paper reviews the progress of lasing mode regulation of ZnO microcavity according to different regulation mechanisms. Firstly, the important progress of traditional static regulated methods, such as cavity structure control and vernier effect, in the lasing mode effective regulation of ZnO microcavity is discussed. Secondly, the dynamic regulation of lasing mode in ZnO microcavity is realized by modulating effective refractive index through piezoelectric or electro-optic physical effects. Finally, the latest progress of surface plasmon effect in the realization of micro and nano cavity laser regulation is summarized. Many traditional methods, with the construction of distributed Bragg reflector (DBR) or distributed feedback (DFB) structure, cavity size control, vernier effect and so on, have been used to realize the lasing mode effective regulation and single-mode-lasing output of ZnO microcavity. However, these traditional methods are only suitable for the pre-designed microcavity structure, and they are highly dependent on the complex micro processing technology. Reducing the size of the cavity will inhibit the acquisition of optical gain, resulting in the increase of optical loss and laser threshold. In addition, these mode regulations are not reversible. In order to solve these problems, many scholars have taken various effective measures. The introduction of surface plasmon, a new physical effect, can make the optical field of ZnO microcavity get better confinement, so as to improve the microcavity gain and reduce the lasing threshold. Based on piezoelectric effect or electro-optic effect, the effective refractive index of ZnO can be regulated, and the dynamic regulation of ZnO microcavity mode can be realized by introducing external stress or external electric field. In addition, the combination of surface plasmon and ZnO nanocavity not only breaks the diffraction limit in size, but also regulates the laser mode in intensity, threshold and mode volume, which provides more theoretical basis and reference value for the future pursuit of nano laser with lower threshold, stronger intensity and smaller mode volume. These methods are not only suitable for ZnO UV laser, but also provide reference for other materials and other band microcavity laser.