Selective 1.3 μm Laser Emission via Coupled Microlaser for Laser Resonance Tuning

A 1.3 μm laser has significant application value in the fields of optical communication and spectral analysis. However, existing optically pumped Whispering-Gallery Microcavity (WGM) are unable to achieve excitation of the 1.3 μm laser due to the stronger fluorescence gain peak of neodymium ions at 1 μm, making it challenging to selectively enhance the 1.3 μm laser mode while suppressing other fluorescence peaks within the WGM microresonator. Here, we construct a coupled microlaser structure composed of two Nd:YAG microdisks to achieve the selection of the 1.3 μm lasing mode in the WGM microcavities. An Nd:YAG crystalline film is exfoliated from the bulk crystal by the ion-implantation-enhanced etching, which is shaped into two microdisks with diameters of 39.5 and 29.1 μm, respectively. And then, these two microdisks are assembled to form a coupled microlaser structure. The Vernier effect of the coupled microlaser enables precise selection and localization of resonant modes at the O-band, providing accurate control over the wavelength of the emitted laser. Our approach achieves 1.3 μm single-wavelength laser emission with a maximum power of 100 μW and a maximum optical conversion efficiency of 1.3%. This work presents the Vernier effect as an effective method for selecting laser modes within WGM resonators, resulting in specific laser emissions that can advance the research and application of WGM microlasers.