We report the development and characterization of 2-D photonic crystal (PC) microcavity devices on silicon on
insulator. The transmission of light through a 2-D PC microcavity near resonance can be switched on and off by
modulating the refractive index of the PC. Because silicon has poor electro-optical properties, it is advantageous to insert
electro-optic materials inside the air holes. In this work, we report the design, fabrication, and characterization of such
hybrid PC microcavity switches using liquid crystals as the electro-optic material. In addition, we demonstrate an
electrode geometry that eliminates electric field screening by the more conducting silicon host, and thus enables
Silicon-based 2-D photonic bandgap (PBG) structures have an unmatched potential for integration with well-established microelectronic devices and circuits. They can allow for compact optical devices with enhanced functionality and performance. While a number of passive PBG silicon-based devices have already been demonstrated, electrical tuning of their properties has yet to be implemented. PBG tuning can be achieved by replacing the air inside the device with active optical material, for example liquid crystals (LCs) or an electro-optic polymer. The two main requirements necessary for tuning in PBG structures are (i) the electric field of the control signal should be present inside the active optical material to modify its properties, and (ii) the energy of the optical mode of interest should be distributed inside the active material. While the latter condition can be satisfied by proper optical design, the former requirement is difficult to satisfy due to external electric field screening by the conductive silicon walls. In this work, an analysis of this effect is conducted and guidelines to overcome screening and thus allow for switching are suggested. Further, by using LCs as an active optical material, electric field switching in 2-D silicon-based PBG structures is demonstrated for the first time. Results of this work can lead to the development of silicon-based switches, active routers and filters for future optical interconnects.
Optical interconnects have begun replacing electrical wires in long distance, backplane applications. As their switching speed and efficiency improves, optical interconnects will penetrate deeper into the device architecture for inter- and intra-chip communications where direct integration with silicon microelectronics is a necessity. Tunable 1D and 2D silicon-based photonic bandgap (PBG) structures are viable building blocks for optical interconnects because they have the capability to redirect light both in- and out-of-plane. In this work, we report on external modulation of the optical properties of 1D and 2D porous silicon PBG structures infiltrated with liquid crystals. This class of eletrooptic modulators offers an inexpensive and versatile way of integrating optical interconnects with standard microelectronic circuits.