= Passive cavity input-output transfer function
{title2=$G(s)=(s-\gamma/2)/(s+\gamma/2)$}
For $\dot a=-\gamma a/2-\sqrt\gamma\,b_0$ and $b_1=\sqrt\gamma\,a+b_0$, zero-initial-data <Laplace transforms> give the displayed <transfer function>. For $\gamma>0$ its pole is in the open left half-plane, while $|G(i\omega)|=1$ and its zero lies in the right half-plane. Passing through $-1$ in this plant's frequency plot is not evidence of an unstable open cavity: a <Nyquist stability criterion> needs an explicitly specified feedback return ratio.
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