Abstract
ZnO optical microcavities have shown great promise as a potential core component material/structure for ultraviolet lasers, light-emitting diodes and photonic sensors because of their outstanding optoelectronic properties. Here, we report a novel ultra-thin-walled 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.
Highlights
Recent developments of optical microcavities have attracted considerable attention and added new opportunities for designing novel micro/ nanophotonic devices, including single-molecule/nanoparticle sensors, on-chip ultra-low-threshold lasers and light-emitting components.[1,2,3] The functional material-based microcavities further provide great potential by combining inherent optical resonance and specific material properties in one platform
The redshift of the near-band edge (NBE) emission and dual peaks near the UV band further indicated the potential of strong ex–ex collisions occurring in the ultra-thinwalled ZnO (UTW-ZnO) microtube
The VZn-related donor–acceptor pair (DAP) emission at room temperature was located in the same band for the optical vapor supersaturated precipitation (OVSP)-grown acceptor-rich ZnO microtubes.[30]
Summary
A novel ultra-thin-walled ZnO microtube cavity supporting multiple optical modes for bluish-violet photoluminescence, low-threshold ultraviolet lasing and microfluidic photodegradation. 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. 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 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 achieved in the UTW-ZnO microtube by WG-WGMs, where the excitation threshold is down to 5.50 μW. NPG Asia Materials (2017) 9, e442; doi:10.1038/am.2017.187; published online 27 October 2017
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