Analysis of Frequency Quadrupling Using a Single LN Intensity Modulator and a Faraday Mirror Based Bidirectional Polarization Rotator for Millimeter Wave Generation

We proposed a novel scheme for frequency quadrupling using a Sagnac loop employing polarization manipulation and a single travelling-wave LN intensity modulator (IM) depending on the velocity mismatch phenomenon. The bidirectional Faraday rotator (BFR) is equivalent to a TE-TM modes converter incorporated in the loop, which is composed of circular connected optical circulators and 90 degrees Faraday mirrors. The undesired sideband is suppressed by properly control the state of polarization (SOP) and the modulation index of the IM. A frequency quadrupled microwave signal is generated with an unwanted harmonic suppression ratio of 27.5 dB.