Ultra-compact and wide-spectrum-range thermo-optic switch based on silicon coupled photonic crystal microcavities

Abstract

We design, fabricate and experimentally demonstrate a compact thermo-optic gate switch comprising a 3.78µm-long coupled L0-type photonic crystal microcavities on a silicon-on-insulator substrate. A nanohole is inserted in the center of each individual L0 photonic crystal microcavity. Coupling between identical microcavities gives rise to bonding and anti-bonding states of the coupled photonic molecules. The coupled photonic crystal microcavities are numerically simulated and experimentally verified with a 6nm-wide flat-bottom resonance in its transmission spectrum, which enables wider operational spectrum range than microring resonators. An integrated micro-heater is in direct contact with the silicon core to efficiently drive the device. The thermo-optic switch is measured with an optical extinction ratio of 20dB, an on-off switching power of 18.2mW, a therm-optic tuning efficiency of 0.63nm/mW, a rise time of 14.8µsec and a fall time of 18.5µsec. The measured on-chip loss on the transmission band is as low as 1dB.Integrated optical switches are important building blocks in silicon photonics. While output-port-selective switches are useful for optical routing applications, optical gate switches with single output port for off-to-on and on-to-off operations also have many potential applications such as optical interconnects and optical logic devices 1,2 . Silicon based optical gate switches have attracted a significant amount of attentions in recent years, due to their small size, large scalability, and potential for integration with wavelength-division-multiplexing (WDM) systems. Since silicon's thermo-optic (TO) effect is significantly larger than its electro-optic (EO) effect, silicon TO switches promises efficient and low-power operation. Conventional MachZehnder interferometers and directional couplers can be used as optical gate switching structures, but they require long waveguides (several millimeters) to obtain π phase shift of light and require relatively high switching power, which limits the integration density and energy conservation 3,4 . Another type of widely-used compact structure for efficient switches a microring resonator. So far, the smallest ring diameter reported is 3µm 5 ; however, one drawback of microring switches is the a

Photonic molecules for improving the optical response of macroporous silicon photonic crystals for gas sensing purposes

“…If a new cavity or a set of them is added to the structure, the optical response cannot only be enhanced but also new functionalities of the system can be obtained. Photon hopping, which consists in the energy transference between adjacent cavities, is one of the most relevant properties of PMs that find its application in coupled-resonator optical waveguides [10][11][12], optical switching [13,14] or quantum information processing [15,16], among others. Furthermore, it has been shown that this energy transfer can be tuned depending on the inter-cavities conformation and on the morphology of the cavities themselves [17,18], leading to enhanced bandwidths and boosted Q-factors [19,20].…”

Coupling length variation and multi-wavelength demultiplexing in photonic crystal waveguides

“…A primary PhC directional coupler is formed by introducing two parallel linear defects into PhCs close to each other. Using the PhC coupler, devices like optical switches [16,17] , optical diodes [18] , and wavelength division multiplexer (WDM)/demultiplexers [19] can be built.…”