Ultralow-Threshold Lasing Based on a One-Dimensional Photonic Crystal Structure with a Liquid-Crystal Defect Layer

• Main Authors: Wang, Hsiao-Tsung, 王筱从
• Other Authors: Lee, Wei
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/93272954465191813743

碩士 === 國立交通大學 === 照明與能源光電研究所 === 102 === In this thesis, a structure enabling enhancement of the local intensity of defect modes in the photonic bandgap is demonstrated by using asymmetric one-dimensional (1-D) photonic crystal (PC) with a liquid-crystal (LC) defect layer. The asymmetric PC structure consists of two multilayer substrates with overlapped bandgaps in the band edges. Owing to the high photon density of states at the photonic band edge, the resulting defect modes exhibit strong resonance in the overlapped region, giving a transmittance of five to ten times higher than that of a symmetric counterpart. Further, a comparison of the characteristics of defect-mode lasing was made between the asymmetric and symmetric 1D PC structures consisting of a dye-doped LC defect layer. We found that the lasing threshold of the asymmetric 1D PC structure to be twenty times lower than that of the symmetric one. The lasing peak can also be controlled by the applied voltage. Therefore, this asymmetric structure holds promise for high-power tunable PC lasers and high-contrast narrow band-pass filter. Besides, the central reflection wavelength can be tuned to the near-infrared region by modulating the optical thickness of the single layer coating in the multilayer for potential applications in tunable optical communication devices.