Abstract

Active microring resonators with whispering gallery mode (WGM) are efficient on-chip light sources. Previously, demonstrations such as semiconductor microrings integrated with gratings for single-mode lasing have been reported [1]. These devices are active-core lasers with gain material contained in the resonant cavity and the laser mode dominated by the WGM. On the other hand, there are also active-cladding lasers, in which a light-emitting polymer is spin-coated onto a linear grating to form an active layer and achieve a continuously tunable wavelength [2]. Although an active-cladding-type laser with a grating integrated microring structure has not yet been reported, if it is demonstrated, propagation modes in radial direction inside the ring can be expected in addition to the microring-specific WGM. In other words, a unique laser device in which different propagating mode groups coexist and are mutually coupled via a diffraction grating on rings can be realized. In this study, we fabricated an active-cladding-type microring laser by spin-coating a laser dye-added polymer onto a Si₃N₄ microring with a diffraction grating and demonstrated and analyzed the coexistence of WGM and radial direction mode for the first time.

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