Improvement of performance and functionality of semiconductor based optical devices including light emitting diodes (LEDs) and laser diodes (LDs) have pioneered various application field and enriched human society. LEDs in ultraviolet to visible light region are mainly fabricated using nitride semiconductors. However, the emission performance of nitride LEDs remain quite low in UVC and red regions. Additionally, nitride LDs have a serious problem of large increase in threshold current. If these problems are solved, the application range will be expanded (e.g., next-generation full-color displays and virus sterilization). 
To solve the above-mentioned problems, I have introduced semiconductor and/or metal nanostructures into optical devices. By exhibiting advantages of nanocrystalline and nanostructural effects, the emission properties of optical devices are improved. In this study, I will promote deeper understanding of optical characterizations for the nanolasers fabricated by the periodic arrangement of semiconductor and/or metal nanostructures. Especially, we will clarify the influence of the nanostructure shape and lattice arrangement on the optical gain and lasing mechanisms.　Through the international collaborative research using high-wavelength resolution spectroscopic measurement systems, we will develop nanolasers with the low threshold power and multi-functionality and thus promote new applications for nanolasers.