Hybrid silicon-conductive oxide nanocavity modulators: toward atto-joule/bit energy efficiency (Conference Presentation)

Abstract

With the exponential growth of bandwidth requirement of data centers and supercomputers, energy already limits our ability to process and communicate information. There is an urgent need to develop low-energy photonic devices and systems that can push the energy efficiency to attojoule/bit level. Traditional silicon photonic modulators rely on the plasma dispersion effect by free-carrier injection or depletion, which occupies a large footprint and consumes relatively high energy for optical interconnects. Here we report an ultra-compact hybrid silicon-conductive oxide electro-optic modulator with total device footprint of 0.6 × 8 μm2. The device was built by integrating voltage-switched transparent conductive oxide with one-dimensional silicon photonic crystal nanocavity. The active modulation volume is only 0.06 µm3, which is less than 2% of the lambda-cubic volume. The device operates in the dual mode of cavity resonance and optical absorption by exploiting the refractive index modulation from both the conductive oxide and the silicon waveguide induced by the applied gate voltage. Such a metal-free, hybrid silicon-conductive oxide nanocavity modulator also demonstrates only 0.5 dB extra optical loss, high E-O efficiency of 250pm/V, and low energy consumption of 3fJ/bit. In addition, we will discuss strategy to further improve the energy efficiency below 1fJ/bit and to achieve high-speed modulation above 10Gbps. The combined results achieved through the holistic design opened a new route for the development of next generation electro-optic modulators that can be used for future on-chip optical interconnects.