||Computation photonics plays a key role in developing modern photonics. Our group research interests are to find effective ways to manipulate electromagnetic waves by using man-made artificial structures such as photonic crystals, metamaterials, and plasmonic structures with computational techniques. First, we study optical properties of photonic crystals, called semiconductors for lights, with similar manners to study electrical properties of semiconductors for manipulating the light propagation and realizing integrative photonic crystal optical devices. Second, we design metamaterials to have unusual optical properties that nature materials cannot exhibit and suggest new paradigm optical devices to break the physical limitation of optical devices. Third, we study plasmon resonances of metallic structures to implement high sensitive sensors and devices to overcome the diffraction limit. In addition, we apply various light manipulation methods for implementing high efficient terahertz sources and passive devices.