All-optical tunable whispering gallery mode lasing in a PMMA-coated microcavity embedded with a high-efficiency nanoheater

A novel all-optical tunable microlaser based on a polymer-coated microcavity embedded with a high-efficiency nanoheater is proposed. The large refractive index contrast between polymer and air helps to generate whispering gallery mode (WGM) resonances, so lasing from polymer microshells can be obtained via total internal reflection. Under the continuous triggering of a 793 nm laser, a maximum photothermal conversion efficiency of 82.9% was achieved using the Nd3+ heavily doped NaGdF4 nanocrystal (NC) as a nanoscale heat source. The nanoheater was doped into the silica core by infrared laser ablation of the microfiber without contact with the WGM, enabling the coated microcavity to maintain a high Q factor up to 1.6 x 106. Significant heat transfer is achieved by the nanoheater absorbing the 793 nm trigger light pumped via the fiber stem, and the lasing wavelength is all-optical tuned over 3 nm at the applied power intensity range of 1 to 1.62 W/mm2. Furthermore, a tuning sensitivity of up to 1.86 nm/(W mm-2) is realized. The excellent photothermal properties of the lanthanide-doped nanoheater make the proposed microlaser attractive for future microelectronic device applications in all-optical networks.

Automated summary

In this research, a novel all-optical tunable microlaser based on a polymer-coated microcavity embedded with a high-efficiency nanoheater is proposed. The large refractive index contrast between polymer and air allows for whispering gallery mode (WGM) resonances, enabling lasing from polymer microshells via total internal reflection. By using a Nd3+ heavily doped NaGdF4 nanocrystal (NC) as a nanoscale heat source, a maximum photothermal conversion efficiency of 82.9% is achieved under the continuous triggering of a 793 nm laser. The nanoheater, doped into the silica core by infrared laser ablation, enables the coated microcavity to maintain a high Q factor up to 1.6 x 106, and significant heat transfer is achieved through the absorption of the 793 nm trigger light by the nanoheater.