Frequency-Doubling OEO Using the Polarization Property of LiNbO3 Modulator

A frequency-doubling optoelectronic oscillator (OEO) has been proposed. In the proposed device, several passive components are introduced into the traditional OEO to handle the polarization state of the laser in the feedback loop. Making use of the polarization dependence of the LiNbO₃ intensity modulator, a special double sidebands modulation is implemented where the polarization direction of the optical carrier is orthogonal with that of the first-order sidebands. Two polarizers are used to choose the specific optical components from the modulated light, which ensures that a microwave signal at the second-harmonic frequency outputs from the OEO when the fundamental frequency signal is self-oscillating in the loop. In the experiment, a 20-GHz frequency-doubled signal was generated, whose phase noise performance and immunity to the polarization drift were measured and evaluated.