UV random laser in aluminum-doped ZnO nanorods

Abstract

Vertically aligned Al-doped ZnO nanorods (AZO-NRs) were grown on glass substrate using a chemical bath deposition (CBD) method at various temperatures between 80°C and 130°C. The results showed the Al content in the AZO-NRs strongly depends on the growth temperature. The optimum doping level was attained at 110°C. The morphology was maintained in each sample, and the lasing properties were investigated against the Al-doped variation. The sample with a high doping level exhibited superior random lasing, with high intensity and spectral width of less than 0.08 nm. The same sample also had the lowest pumping threshold of 0.192 mW. More importantly, this study showed the possibility of utilizing doping as a tuning parameter for random lasing, whereby a 7.3 nm redshift in the lasing peak was observed with increasing doping concentration. This study also placed an emphasis on AZO-NRs as potential candidates for tunable random laser devices.

Review of Open Cavity Random Lasers as Laser-Based Sensors

“…Tunability can be achieved by changing the weight fraction, particle size, and photonic crystal lattice and adding a nonfluorescent dye to the gain medium . A more recent approach to tuning a random laser is by doping the gain material with metal or inorganic elements that shifts the bandgap of the material. ,, The threshold for these doped random lasers varies but is much smaller (at least 1 order of magnitude) than the material without doping elements.…”

“…53 A more recent approach to tuning a random laser is by doping the gain material with metal or inorganic elements that shifts the bandgap of the material. 6,54,101 The threshold for these doped random lasers varies but is much smaller (at least 1 order of magnitude) than the material without doping elements. ■ LASER-BASED SENSING OVERVIEW Laser-based sensors have been reported to address critical challenges in creating reliable, real-time, and cost-effective monitoring integrated systems which are robust to changes in chemical composition over extended periods of time.…”

“…For a random laser to be adopted into any existing technology, the lasing threshold must be small, which is at present still a challenge for random lasers. As such, significant progress has been made over the years to further improve random lasers by improving the design and attributes of a random laser design that significantly lowers the lasing threshold, enhance the lasing emission and lasing intensity as well as providing lasing tunability elements that may be of paramount importance for ultrasensitive sensing. − A review of current threshold values obtained for various materials is presented in the section Improvements in Lasing Threshold. This includes fundamental investigations into improving control over the random lasing threshold and scattering characteristics that can bring new opportunities to utilize such open cavity random laser systems for a range of applications such as cancer detection, photodynamic therapy, document encoding, displays, speckle-free imaging, microscopy, and sensing applications. − …”

Ex-situ doping of ZnO structures as potential random lasers

“…Since geometry and wavelength of random laser may be adjusted, this has an extra benefit for a variety of applications, including sensors that detect dopamine, pH, UV radiation and acetone gas [1]- [3]. For random lasers, lowering lasing threshold, wavelength tunability, and emission directionality remain challenging to achieve [4]. However, numerous types of research have been done to address this problem, including developing a distinctive light source [5], integrating white RL on a chip [6], employing dye-doped liquid crystals [7], and using ZnSe crystal [8] in a random laser system.…”

“…Both in-situ and ex-situ methods can be conducted. However, the maximum limit of doping concentration for random laser synthesized by CBD using the in-situ doping technique was between 5 mM [10] and 10 mM [4]. By using the ex-situ doping approach, doping concentration can be increased.…”