Integratable 40dB optical waveguide isolators using a resonant-layer effect with mode coupling

Resonant-layer effect (RLE) optical isolators can be integrated with a wide variety of optical waveguide devices and systems and theoretically provide a high degree of isolation with low insertion loss. The effect of mode coupling within the isolator and the losses due to coupling between the isolator and the input and output waveguides on the performance of RLE isolators is calculated. The results predict that isolators integrated with semiconductor waveguides similar to those used for efficient lasers and amplifiers and isolators integrated with quartzlike waveguides can give 40dB of isolation with insertion losses below 3dB. The calculations also show relaxed dimensional tolerance and lengths in the 1–2mm range, which makes commercial production of such isolators attractive.