To develop novel optical microstructures with potential in photonic, microfluidic, biomedical, and micromechanical applications, scientists at the State Key Laboratory of Optoelectronic Materials and Technologies at Zhongshan University (Guangzhou, China) have created a technique to fabricate complicated three-dimensional (3-D) photonic crystals using single-exposure holographic laser lithography. Seven linearly polarized laser beams in two configurations were used to create an interference pattern deposited on a photoresist film 40 µm thick. After polymerization, development, and drying, the 3-D pattern measured 25 µm, and consisted of a hexagon motif (a kagome lattice) on the surface with a chainlike lattice on the cleavage plane.
Transmission through three different layers of the hexagonal microstructure creates a diffraction pattern resembling fireworks. Transmission spectra reveal a dropoff below about 1700 nm, with a partial photonic bandgap between 1.9 and 2.25 µm. The next step in the plan, according to team member He-Zhou Wang, is to fabricate new photonic crystals with wide bandgaps in the visible. Such structures will have novel properties that can be exploited much like those of well-known electronic crystals. Contact He-Zhou Wang at [email protected].