Efficient broadband composite optical isolator

A new design of a broadband optical isolator, composed as a sequence of ordinary Faraday rotators and achromatic quarter-wave plates (QWPs), is presented. In particular, we demonstrate that by using four Faraday rotators and six achromatic QWPs, rotated at specific angles, optical isolation better than 15 dB over the range from 700 to 1000 nm can be achieved. The measured transmittance (corrected for absorption and reflection) in the forward direction over the same wavelength range shows broadening of the transmission spectrum compared with the one of a single Faraday rotator.