New spherical optical cavities with non-degenerated whispering gallery modes

Tsutaru Kumagai; Giuseppe Palma; Francesco Prudenzano; Tetsuo Kishi; Tetsuji Yano

doi:10.1117/12.2251599

20 February 2017 New spherical optical cavities with non-degenerated whispering gallery modes

Tsutaru Kumagai, Giuseppe Palma, Francesco Prudenzano, Tetsuo Kishi, Tetsuji Yano

Proceedings Volume 10090, Laser Resonators, Microresonators, and Beam Control XIX; 100901F (2017) https://doi.org/10.1117/12.2251599
Event: SPIE LASE, 2017, San Francisco, California, United States

Abstract

New spherical resonators with internal defects are introduced to show anomalous whispering gallery modes (WGMs). The defect induces a symmetry breaking spherical cavity and splits the WGMs. A couple of defects, a hollow sphere (bubble), and a hollow ring, have been studied. The hollow sphere was fabricated and the splitting of WGM was observed. In this paper, this "non-degenerated WGMs (non-DWGMs) resonance" in a microsphere with hollow defect structure is reviewed based on our research. The resonance of WGMs in a sphere is identified by three integer parameters: the angular mode number, l, azimuthal mode number m, and radial mode number, n. The placement of the defect such as a hollow ring or single bubble is shown to break symmetry and resolve the degeneracy concerning m. This induces a variety of resonant wavelengths of the spherical cavity. A couple of simulations using the eigenmode and transient analyses propose how the placed defects affect the WGM resonance in the spherical cavity. For the sphere with a single bubble defect, the experimentally observed resonances in Nd-doped tellurite glass microsphere with a single bubble are clarified to be due to the splitting of resonance modes, i.e., the existence of "non-DWGMs" in the sphere. The defect bubble plays a role of opening the optically wide gate to introduce excitation light for Nd³⁺ pumping using non-DWGMs in the sphere efficiently.

Conference Presentation

Citation Download Citation

Tsutaru Kumagai, Giuseppe Palma, Francesco Prudenzano, Tetsuo Kishi, and Tetsuji Yano "New spherical optical cavities with non-degenerated whispering gallery modes", Proc. SPIE 10090, Laser Resonators, Microresonators, and Beam Control XIX, 100901F (20 February 2017); https://doi.org/10.1117/12.2251599

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