Sol–Gel ZnO–SiO<tex>$_2$</tex>Composite Waveguide Ultraviolet Lasers

UV Random Lasing Action in p‐SiC(4H)/i‐ZnO–SiO2 Nanocomposite/n‐ZnO:Al Heterojunction Diodes

“…UV random lasing can be achieved in these films because the appropriate patterning of ZnO clusters enhances the optical quality (i.e., higher gain and lower loss) of the random media. [4] Furthermore, the sandwiching of nanoparticles between the electron-and hole-injection layers has been shown to enhance the injection efficiency of the carriers so that the nanoparticles can attain a high optical gain under electrical excitation. [5,6] Hence, if patterned ZnO-SiO 2 nanocomposite films can be used as the intrinsic layer of ZnObased heterostructural p-i-n junctions, [7] UV random lasing may be achieved.…”

“…The emergence of sharp peaks, which are attributed to a coherent random lasing action, is due to the presence of stripe patterns that allow the formation of closed-loop random cavities. [4,8] In order to verify that the sharp peaks correspond to the formation of closed-loop random cavities, Fourier transform (FT) was used to analyze the EL spectra obtained at high injection currents. The corresponding FT spectrum, as shown in the inset of Figure 3b, exhibits periodic features, indicating the formation of closed-loop paths.…”

“…[4,8] The peak wavelengths of the 60 nm ZnO powder and the ZnO:Al(1 %) film are found to be ca. 382.7 and ca.…”

Lasing characteristics of random cylindrical microcavity lasers

“…Coherent random lasing has been observed from strong scattering media with high optical gain such as highly disordered ZnO thin films and nanocomposite films with ZnO powders. 1,2 Although narrow linewidth can be obtained from these random lasers via formation of closed-loop random cavities, high pumping threshold, and multiple lasing modes of random media hinder their practical applications. 3 In order to improve the lasing characteristics of random lasers, efficient optical confinement of random media was used to suppress the excitation of random modes.…”

“…The laser emission was collected from the edge of the sample through an objective lens. It can be shown that the composite film exhibits random lasing action with pump threshold, I th , at around 60 kW/cm 2 . In addition, the number of lasing modes increases from $4 to $15 for the excitation pump increases from $1.0 Â I th to $1.4 Â I th , respectively.…”