Discussion Forum

I want to study the surface acoustic wave propagation in gallium nitride. I have a problems about attenuation of the wave.

The problem is that I don't know how to use the loss factor in COMSOL when I want to study the attenuation of the surface acoustic wave in gallium nitride. The loss factor in COMSOL is defined as the storage modulus over the loss modulus, which is not the same as we describe loss in new piezoelectric materials usually. We define that the loss factor usually as A = 20*lg (Uo/U) / L. Uo is the electric potential applied initially while U is the electric potential where is L far away from the transducers on which we apply the electric potential. So the unit of the loss factor is dB/m. Or sometimes we use dB/lambda, where lambda is the wavelength of the surface acoustic wave. This is like the loss modulus. The problem is we don't have a storage mudulus. We cannot say that the Uo-U is the storage modulus. Moreover, Most of the papers about experimental research on attenuation in gallium nitride do not use imaginary part to describe the loss. So I really don't know how to put this equation into COMSOL. Or, is there a better way to capture the feature of attenuation of surface acoustic wave, like the anisotropic loss which is more accurate?

Thank you.