The proposed device was designed and fabricated by using z-cut LiTaO3 crystal. First, periodically poled structure was fabricated in a 0.4mm thick crystal substrate by use of the pulse voltage applying method. The period of poling, 2L, was set to 10.2mm for QPM between the modulated lighwave at wavelength of 1550nm and the microwave at designed frequency of 15GHz. Next, the periodically poled crystal was cut by a diamond saw. The total length, Lt, along the propagation direction was 40mm and the cross section, a×b, was 2.0×0.4mm2. This cross section size was designed for a single-mode structure at frequency range of 13GHz-19GHz. After cutting, both ends of the crystal were polished. Finally, a 2μm Al thin film wasdeposited on the four side walls of the crystal by use of electron beam vapor deposition.