Lasing from ZnO nanorods on ITO-coated substrates

Abstract

Lasing was observed from ZnO nanorods prepared by a simple method of chemical bath deposition (CBD) on ITOcoated glass substrates. The X-ray diffraction pattern showed a dominant peak for (002) plane typical for good crystalline quality of ZnO grown in the z-direction with a wurtzite structure. Continuous-wave photoluminescence (PL) spectra revealed a peak centered at 380 nm corresponding to the band gap of ZnO. Under pulsed optical pumping, lasing was observed above the nominal PL peak, initially for one mode at 384 nm. Two additional modes at 386 nm and 390 nm was observed when the pumping power is further increased. Threshold was achieved at 0.7 µJ which was 10 times smaller than that reported for powder-based random lasers. In addition, gain pinning was also observed for the dominant mode and the additional two modes appeared upon onset of this gain pining behavior.

Influence of Al doping on random lasing in ZnO nanorods

“…4(b), shift in lasing wavelength with increasing pump power was less than 0.05 nm and no additional peaks appeared indicating the stability of the lasing emission. Fixed number of modes with increasing pump power has been observed in our previous work from ZnO nanorod matts however there was a shift in wavelength with increasing pump power between 0.2 nm and 0.5 nm depending on the morphology of the sample [11,32,35]. The stability of the lasing emission from this work suggests that slight doping in preparing ZnO nanorods using chemical bath deposition method is a good way of making stable random lasers.…”

“…Threshold reduction may be related to the transport mean free path which is affected by changes in rod density, length and size [30]. However, threshold reduction is always less than one order of magnitude [7,11,31,32]. Such large threshold changes, when compared with undoped ZnO, is implying that the aluminum embedded in the nanorods is responsible in reducing the threshold.…”

Review of Open Cavity Random Lasers as Laser-Based Sensors

“…For rhodamine, the emission is between 550 and 610 nm. For ZnO random lasers, the emission is at ∼380 nm, and for gallium nitride (GaN) the emission is ∼365 nm. , Small changes in the emission wavelength are likely to occur in semiconductor nanostructures due to minor changes in the bandgap from small fluctuations of the size of nanostructures, mostly observed from ZnO. − Figure shows the different random lasing emission wavelengths observed from several materials upon achieving the threshold. As observed from the figure, random lasers prepared by ZnO and GaN (as well as most solid-state semiconductor random lasers) show multiple emissions.…”

“…Emission spectra of (a) rhodamine dye mixed with TiO 2 nanoparticle at several pump powers with a concentration of 2 × 10 11 cm –3 , (b) GaN nanocolumns, and (c) ZnO nanorods. ,, …”

“…The current state of laser-based optical biosensors has mostly evolved around the use of laser dyes as a gain medium. − Such dye-based sensors typically result in a broad lasing spectrum (10 to 30 nm line widthwhich is comparable to fluorescence-based sensors) and are subject to degradation of the laser dye. As such, solid-state gain medium for random lasers has been extensively investigated by researchers to replace the need for laser dyes to achieve lasing. − Certain types of random lasers employing a solid-state gain medium with high scattering provided by the gain medium itself and have been shown to provide a narrow emission line. − Hence, degradation issues could be addressed by employing a solid-state gain medium with current laser-based biosensors. A review of random laser-based biosensors is provided in detail in the section Random Laser Biosensors.…”