Ultra-Broadband Modulator Packaging for Millimeter-Wave Applications

This paper reports the RF packaging design for electrooptic modulators operating in the millimeter-wave domain and discusses the RF and optical performances of the module. An LiNbO₃ phase modulator has been integrated in a compact housing offering a 1.0-mm RF coaxial input connector. A coplanar waveguide on a low dielectric-loss alumina substrate has been designed to transition the RF field from the connector to the modulator. A RF insertion loss in the 1-2.5-dB range has been measured for the module over the 70-110-GHz bandwidth. A half-wave voltage comprised between 8.6 V at dc and 20 V at 110 GHz was calculated based on the observation of the optical modulation sidebands over the entire 110-GHz bandwidth. The optical insertion loss of the module was measured at 2.8 dB.