III-nitride tunable cup-cavities supporting quasi whispering gallery modes from ultraviolet to near infrared

TL;DR

This paper reports on III-nitride cup-cavities capable of supporting tunable whispering gallery modes across ultraviolet to near-infrared spectra, with mode switching and stable emission properties at room temperature, advancing nanophotonic device integration.

Contribution

Introduction of epitaxial, site-controlled III-nitride cup-cavities supporting tunable modes from ultraviolet to near-infrared with mode switching and stable emission characteristics.

Findings

Support for quasi whispering gallery modes up to room temperature

Mode switching caused by refractive index variation near absorption edge

Stable narrow emission lines with consistent energies in large cavities

Abstract

Rapidly developing nanophotonics needs microresonators for different spectral ranges, formed by chip-compatible technologies. In addition, the tunable ones are in greatest demand. Here, we present epitaxial site--controlled III--nitride cup--cavities which can operate from ultraviolet to near--infrared, supporting quasi whispering gallery modes up to room temperature. In these cavities, the refractive index variation near an absorption edge causes the remarkable effect of mode switching, which is accompanied by the change of spatial intensity distribution, concentration of light efficiently into a subwavelength volume, and emission of terahertz photons. At a distance from the edge, the mode-related narrow emission lines have stable energies and widths at different temperatures. Moreover, their energies are identical in the large 'ripened' monocrystal cavities. Our results shed light on the mode behavior in the semiconductor cavities and open the way for single--growth--run manufacturing the devices comprising an active region and a cavity with tunable mode frequencies.