New design of a polarization-independent optical isolator with high performance

A novel design of a polarization-independent optical isolator is proposed, which consists of birefringent plates as spatial walk-off polarizers, halfwave plates, and a conventional polarization-dependent optical isolator. In this design, it is not hard to make alignment of its components because the backward light is interrupted by the conventional isolator. One can easily obtain a high isolation keeping insertion loss low by utilizing a conventional cascaded polarization-dependent optical isolator. The measured insertion loss of the new isolator is only 0.33 dB and the isolation is over 65 dB at the wavelengths of 1310 and 1550 nm. The dependence of the insertion loss on the polarization is within 0.02 dB at each wavelength. In the range of wavelength from 1290 to 1330 nm and from 1530 and 1570 nm, this isolator has a high isolation of more than 50 dB and a low insertion loss of less than 0.4 dB at room temperature. It shows the same high performance for variations of temperature between -20 and 80°C