Enhancing radiation control of an optical leaky wave antenna in a resonator

We analyze the theoretical and physical properties of a CMOS compatible optical leaky wave antenna (OLWA) integrated into a Fabry-Perot resonator (FPR) at 193.4 THz (wavelength lambda(0) = 1550 nm). The presented OLWA design is composed of a silicon (Si) dielectric waveguide sandwiched between two silica glass (SiO2) domains, and it comprises periodic perturbations (cavities of vacuum). We first describe the radiation of the isolated OLWA whose radiation pattern is due to the excitation of a leaky wave, slowly decaying while traveling. The perturbations are indeed designed to obtain a leaky wave harmonic with very low attenuation and phase constants. Then, we integrate the same OLWA into a FPR where two leaky waves with the same wavenumber are travelling in opposite directions inside the resonator. We show that the radiation level at the broadside direction can be effectively controlled by modifying the optical properties of the Si waveguide through electron-hole excess carrier generation (found to be highly enhanced when it is integrated into a FPR). The design of the integrated OLWA is properly set to guarantee the constructive interference of the two radiated beams provided by the two leaky waves in the FPR. The modal propagation constant in the integrated OLWA can be then altered through excess carrier generation in Si, thus the antenna can be tuned in and out of the resonance thanks to the high FPR quality factor, and the LW modal dispersion relation. This allows for enhanced radiation level control at broadside, and preliminary results show up to 13 dB beam modulation.