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Leaky mode solution from coefficient form PDE
Posted Nov 5, 2020, 11:03 p.m. EST Acoustics & Vibrations 0 Replies
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Hi,
I try to find the leaky mode from an antiguiding acoustic waveguide. The waveguide has a high velocity core (silica) suspended in a low velocity enviroment (air). I use the coeffcient form PDE solver and specifying coefficients accordingly to have a standard wave equation. PML layer is applied outside of the cladding environment.
In the wave equation, the propagation constant is given and real as it is dictated by the optical effect that generated the acoustic wave (Stimulated Brillouin scattering). The eigenvalues the solve find will be the complex frequency. I specifed the range for the eigenvalues to be found in from 1/V_core to 1/V_clad imaginary values.
Comsol did not find any meaningful solution for the configuration above. Instead it seems to find guided acoustic modes in the cladding (low velocity) with a little evanecesent field extending into the core region. What I hope to find is a well confined "leaky" modes in the core due to the large difference in sound impedence between the core and cladding, as per this paper (fig. 9)
https://arxiv.org/ftp/arxiv/papers/1308/1308.0382.pdf
Greatful to have any suggestion.
Hello Linh Nguyen
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