A novel ultra-thin-walled ZnO microtube cavity supporting multiple optical modes for bluish-violet photoluminescence, low-threshold ultraviolet lasing and microfluidic photodegradation

Abstract

ZnO optical microcavities have shown great promise as a potential core component material/structure for ultraviolet lasers, lightemitting diodes and photonic sensors because of their outstanding optoelectronic properties. Here, we report a novel ultra-thinwalled ZnO (UTW-ZnO) microtube cavity with a wall thickness of~750 nm, supporting multiple types of optical modes, including in-tube Fabry-Perot modes, in-wall Fabry-Perot modes and wave-guided whispering gallery modes (WG-WGMs). The free-exciton recombination rate and exciton-exciton collisions are promoted in the cavity. The intensities of near-band edge (ultravoilet (UV) light) and X-band (blue light) emission are therefore increased at least one order of magnitude in the temperature range of 0-500°C. Meanwhile, the temperature-sensitive multicolor luminescence of the UTW-ZnO microtubes in the visible band from near-white to bluish-violet is demonstrated for the first time. Low-threshold UV lasing is also achieved in the UTW-ZnO microtube by WG-WGMs, where the excitation threshold is down to 5.50 μW. Furthermore, light harvesting in the microtube cavity is beneficial to boosting the ZnO catalytic performance for photodegradation of organic dyes. The UTW-ZnO microtube exhibits compatibility to microfluidic channels for recyclable on-chip degradation. The present work provides new opportunities to design novel tubular wide-bandgap semiconductor devices for a variety of optoelectronic applications in micro/ nanophotonics.

Evolution of Whispering Gallery Modes in Li-Doped ZnO Hexagonal Micro- and Nanostructures

“…In this paper, the evolution and quality of the resonant peaks in relation to the size and shape of the resonant cavity and to the reflectance efficiency of the facets are described. It was shown that doing measurements that mapped the evolution of the optical resonant modes along the length of the structure will helped to identify the regions with resonant cavities that had better performance for applications such as lasing [2,3,13,14], sensors [12], immunosensors [15], or optical filters [16][17][18].…”

Current-Induced Thermal Tunneling Electroluminescence in a Single Highly Compensated Semiconductor Microrod

“…Our previous work has confirmed V Zn acting as stable recombination centers up to 773 K (Wang et al, 2016(Wang et al, , 2017a. Figure 3E shows the temperature-dependent PL spectra of a 15%-O 2 HC-ZnO microrod measured by a CW 325-nm-line He-Cd laser with the polarization perpendicular to the c-axis.…”

“…Figure 1A shows the setup for growth of HC-ZnO microrods with massive V Zn -related acceptors and Vorelated donors, as proposed in our previous studies (Hu et al, 2018b;Wang et al, 2016Wang et al, , 2017aWang et al, , 2017b. To efficiently control the V O concentration, the O 2 /Ar mixed carrier gas with variable oxygen pressure ratios (i.e., 15%, 20%, and 25%) was used during OVSP growth; a mixture of ZnO and graphite powders with a definite weight ratio of 2:1 was pressed as the reactive green body rod.…”

“…The missed V 1-Zn -V 2-Zn transition was due to the cutoff detection energy of the spectrometer (1.0 eV). The FA transition from the CBM to V 1-Zn (e-V 1-Zn ) was suppressed owing to the high binding energy of V 1-Zn for DAP recombination (Wang et al, 2016(Wang et al, , 2017a.…”

“…Our previous work has demonstrated the stable acceptor-rich ZnO (A-ZnO) microrods/tubes grown by temperature-gradient-free optical vapor supersaturation precipitation (OVSP) (Hu et al, 2018a(Hu et al, , 2018bHuang et al, 2019;Wang et al, 2016Wang et al, , 2017aWang et al, , 2017bWang et al, , 2019b. The Zn vacancy (V Zn ) acted as an acceptor level, activating donor-acceptor-pair (DAP) recombination with intrinsic compensation donors, i.e., oxygen vacancy (V O ), for visible photoluminescence (PL) emission up to 773 K (Wang et al, 2017a). It forms a robust and generic luminescent center in wide band-gap semiconductors for high-temperature EL emission.…”