Ultrafast Hybrid Active Materials and Devices for Compact RF Photonics

The proposed research is targeted at developing revolutionary ultrafast photonic devices within the silicon system. The goals of this two-phase program include: (1) Demonstrating all-optical on-chip gain at speeds of several terahertz in a silicon-organic hybrid waveguide system. This will be a demonstration of an all-optical transistor equivalent, operating at speeds well in excess of what can be achieved in electronics. (2) Building ultra-low-voltage electro-optic modulators based on organic-clad nanoslot waveguides. The Hochberg group currently holds the world record for the lowest voltage electro-optic modulator (0.25V), and has shown that their approach can be radically improved with further work. With the proposed approach, it will become possible to create modulators that provide significant gain from the electrical-to-optical transition. This will radically change the fundamental tradeoffs in the design of radio frequency and millimeter wave systems, from radars to high speed analog signal processing chips. Both of these devices will bring the benefits of integrated optics (particularly radically reduced size, weight, and power for hugely complex systems) to defense-critical signal processing and RF photonics applications. These two new classes of device will serve as proofs-of-concept for the use of silicon-organic hybrid technology as a practical platform for nonlinear optics. BENEFIT: This proposal focuses on developing revolutionary, ultrafast silicon photonic devices using silicon-organic hybrid technology. Today, all-optical modulators with signal gain at THz bandwidth simply do not exist, and EO modulators with sub-1 Volt bias-free Vπ values do not exist. Practical chip-scale all-optical modulators with THz bandwidth and signal gain could become the basis of ultra-high-speed all-optical logic on-chip. The most notable application for such a capability would be as a path to higher bandwidth logic than is possible with conventional electronic millimeter-wave integrated circuits. Low-power EO modulators could radically alter the design of RF photonic systems, eliminating the need (for instance) to amplify signals coming off of antennas before launching the RF signals onto an optical fiber. The best competing technologies for highly linear analog modulators, based on lithium niobate, use a very mature technology which is unlikely to scale below a couple of volts Vπ at 20 GHz (for example). Our approach offers a path to 2-3 order-of-magnitude improvements in operating voltage, and 4-6 order-of-magnitude improvements in operating power. Very low voltage EO modulators, coupled to sensitive on-chip antennas, may also provide the basis for ultra-sensitive electric field and RF probes, and as components of revolutionary analog-over-fiber systems. The Hochberg laboratory has demonstrated world-record low voltage electro-optic modulators with this approach as bench prototypes, operating at low speeds. And they have shown that their approach can be scaled-down by additional orders of magnitude through the use of advanced lithography and modern electro-optic materials. Their process has the potential to radically change the fundamental tradeoffs in the design of radio frequency and millimeter wave systems, from radars to high speed analog signal processing chips. In addition, this type of device may find wide application in the data communications market, where EO modulators provide the gateway between electronic circuits and optical fibers.