Modified Photonic Band Gap Via Thermal Shrinkage of Two-Photon Polymerized Distributed Bragg Reflectors

One-dimensional (1D) polymer-based photonic crystals (PhCs) in the $1.55\ \mu \mathrm{m}$ wavelength range can be easily created using a two-photon direct laser writing system. To achieve shorter period structures, we report the use of thermal shrinkage [1]–[3] of two-photon polymerized structures at elevated temperatures to eliminate unpolymerized material, leading to the uniform shrinkage of distributed Bragg reflector (DBR) structures [4] by a ratio of 2.5 to 5. Our Finite difference time domain (FDTD) simulation and the angle-resolved light scattering characterisation technique using Fourier image spectroscopy (FIS) [5]–[7] show that the photonic bandgap (PBG) of DBRs blue-shift in the visible region (650 nm to 500 nm).