We describe the distinguishing characteristics of coherent perfect optical conversion processes using two-beam interference, as compared to single-beam ‘critical coupling’ processes. We extend the application of two-port coherent conversion processes to magneto-optical (Faraday) rotation in structured systems and present our recent laboratory demonstration of coherent perfect polarization rotation (CPR) which is a conservative, reversible counterpart to coherent perfect absorption (CPA, or the so-called ‘antilaser’). conclude with a brief summary of theoretical studies suggesting a CPR-based miniaturization of optical isolators and the extension of coherent perfect phenomena in non-linear optics.