Dual-wavelength switchable single-mode lasing from a lanthanide-doped resonator

Multi-wavelength lasing, with dynamic switching functionality, high spectral purity and contrast, plays an essential role in photonic devices. Lanthanide(Ln3+)-doped upconversion nanocrystals(UCNCs) featured with plentiful energy levels act as ideal candidates for the gain medium. However, it remains a daunting challenge to develop a tunable Ln3+-based single-mode laser across a wide wavelength range due to the absence of an appropriate mode-selection mechanism. Here, we have demonstrated the first active control of unidirectional single-mode lasing with switchable wavelength spanning beyond a record range (~ 300 nm). This is accomplished through the integration of two size-mismatched coupled microdisks cavity and inversely designed dual-mode UCNCs incorporated with selective sensitizer-pair and activator ions. By asymmetric pumping, a reversible and crosstalk-free ultraviolet-to-red single-mode operation were formed respectively from such UCNCs-based system through changing the pumping wavelengths from 980 nm to 808 nm. The results enlighten the rational design of luminescent materials and microcavity. With remarkable doping flexibility, our approach would pave an avenue to a class of UCNCs-based photonic devices for on-chip optical filter, switch, sensor and other devices.