Intrinsically resonant traveling-wave Y-fed directional couplers at high frequency

Traveling-wave Y-fed directional couplers are shown to have a high-frequency bandpass response because of the inherent velocity mismatch between the optical and electrical waves. Furthermore, if their characteristic parameters are suitably chosen, it is possible to achieve an intrinsic resonance by using uniform electrodes. These principles are theoretically investigated and experimentally demonstrated at center frequencies up to 8.5 GHz for titanium indiffused in lithium niobate (Ti:LiNbO3 ) waveguides at 1.3 μm wavelength.