Novel wireless millimeter-wave to lightwave signal converters by electro-optic crystals suspended to narrow-gap-embedded patch-antennas on low-k dielectric substrates

We propose a new wireless millimeter-wave (MMW) to lightwave (LW) signal converter using an electro-optic crystal suspended to narrow-gap-embedded patch-antennas on a low-k dielectric substrate. Wireless MMW signals can be received by the patch-antennas and converted to LW signals by use of the MMW electric field across the narrow-gap for electro-optic (EO) modulation. An aperture area of the patch-antennas is about 4 times larger than that fabricated on a high-k EO crystal only as the substrate. The MMW electric field across the narrow-gap of the proposed device also becomes 10-times stronger than that using the high-k dielectric EO substrate. Therefore, the conversion efficiency enhancement of approximately 20 dB can be obtained using the proposed device. It is compact, passive, and operated with extremely low MMW distortion in high-speed radio-over fiber communication and measurement systems.