Two-photon polymerization has been demonstrated as an effective technique to define embedded defects in three-dimensional photonic crystals. In this work we demonstrate the ability to precisely position embedded defects with respect to the lattice of
three-dimensional photonic crystals by imaging the structure concurrently with two-photon writing. Defects are written with near-perfect lattice registration and at specifically defined depths within the crystal. The importance of precise defect position is demonstrated by investigating the optical properties of embedded planar cavities written in a photonic crystal. The experimental data is compared to spectra calculated using the Scalar Wave Approximation (SWA) which further demonstrates the importance of defect placement.
