Abstract-The detection of a 15GHz optical modulation signalwas demonstrated experimentally by using difference frequencygeneration (DFG) in a periodically-poled LiTaO3 microwaverectangular waveguide with a resonator structure. Couplingbetween the fabricated device and a measuring antenna wasimproved by utilizing a microwave lens. The detected signalpower was enhanced by about 20dB compared with the powermeasured without the microwave lens.