Optical isolation based on nonreciprocal phase shift induced by interband photonic transitions

Photonic transitions in waveguides can create nonreciprocal phase response for counterpropagating modes. Such effect can be used in Mach-Zehnder interferometers to form optical isolators and circulators. Performance of such device is analyzed using coupled mode theory given the experimentally available modulation in silicon. The proposed scheme can provide a broadband (>0.8 THz), high contrast ratio (>20 dB) optical isolation at telecommunication wavelength.