Spontaneous pattern formation in an absorptive system

We present analytical and numerical results indicating pattern formation in a purely absorptive medium, namely a resonantly-excited two-level system in a ring cavity. Pattern formation occurs when the cavity is mistuned such that the optical wavelength exceeds that of the nearby cavity mode. But then off-axis or "tilted" waves can exactly fit the cavity, and this determines the dominant transverse wave vector of the pattern.<
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