Optofluidic Dispersion Engineering of Photonic Crystal Waveguides

Optofluidics, the marriage of photonics and microfluidics, uses the inherent flexibility of confined fluids to reversibly tune photonic structures beyond traditional fabrication methods. Photonic crystals (PhCs) are well suited to optofluidic tuning; their periodic air-hole microstructure is a natural candidate for housing liquids. This microstructure enables PhCs to strongly control light on the wavelength scale. Defects purposefully introduced during PhC fabrication can support guided optical modes, forming waveguides or cavities; their dispersion can be engineered by fine alteration of individual PhC holes in or around the structure. This engineering requires very high fabrication tolerances and is irreversible once performed. Optofluidic tuning of PhC waveguides, however, is completely reversible and only limited by the properties of available fluids. Infiltration of the PhC microstructure surrounding a waveguide modifies the local refractive index profile through the liquid used and the amount of microstructure filled. In this paper we demonstrate experimentally for the first time, optofluidics dispersion engineer of photonic crystals waveguides. We have modified the group velocity dispersion using a technique based on selective liquid infiltrations to precisely and reversibly change our structures. We also present how the amount of fluid infiltrated into the photonic crystal microstructure strongly influences the waveguide dispersion.