Abstract
Photonic crystals with periodic variations in dielectric constants can theoretically exhibit forbidden gaps as a result of Bragg diffraction, thus prohibiting electromagnetic wave transmissions. The diffraction wavelengths are comparable to the lattice constants. In this study, diamond-type dielectric lattices with isotropic periodicities were identified as the perfect structure to open photonic band gaps for all crystal directions, and were then successfully processed. Stereolithographic additive manufacturing was customized to create photonic crystals with micro-sized diamond-like lattices. Photosensitive acrylic resin containing alumina nanoparticles was spread on a glass substrate with a mechanical knife edge. Cross-sectional layers, photo-polymerized by micro-pattern exposures, were laminated to create composite precursors. Next, dense components were obtained by dewaxing the precursors and subjecting them to sintering heat treatments. Structural defects consisting of point- and plane-cavities were introduced into the diamond photonic crystals by using computer-aided design, manufacture, and evaluation in order to study the characteristic resonance modes. These lattice misfits localize the electromagnetic waves strongly through multiple reflections, and wave amplifications enable transmission peak formations in the photonic band gaps according to the defect size. These photonic crystal resonators with micro-lattice patterns can be applied as wavelength filters in the terahertz frequency range. Terahertz waves in the far infrared range can be used in various types of novel sensors to detect dust on electric circuits, defects on material surfaces, cancer cells in human skin, and bacteria in vegetables.
