FIGURE 4.

The real parts and imaginary parts of the depth-related term. (A) Real parts of the depth-related term $\stackrel{\sim }{\mathrm{\Phi }}$ . (B) Imaginary parts of $\stackrel{\sim }{\mathrm{\Phi }}$ . The cavity depth (pure water thickness) includes 90, 130, 170, and 210 μm “∞” indicates the thickness of pure bulk water, for which either the real part or the imaginary part of $\stackrel{\sim }{\mathrm{\Phi }}$ is zero for the frequency range investigated.