Development of Photonic Crystals for Radiation-Field Control

1.利用最先进的半导体微机械加工技术，成功地从Al_xGa_(1-x)As中制备了三种类型的二维(2D)或准三维光子晶片。然后，我们简化了这些样品的光学响应，如使用飞秒光脉冲观察到的特定波长的透射谱和反射率。因此，我们从控制辐射场和光传播的角度出发，用计算出的相应的光子能带结构对这些样品进行了表征：(1)光波导板在下包层中段周期性穿孔，阐明了尽管不存在导模，但空气填充因子小于0.3，空气孔行数小于10的样品应达到上述目的。(2)无包层的空气桥板；发现存在导模，其透过率几乎为100%，且这种类型的样品具有较好的性能。(3)下包层氧化以降低折射率的平板；由于导模存在于有限的能区，因此这种类型的样品也是很好的。我们利用上述平板样品或由PBO光纤制成的2D毛细管型空气棒晶体，在实验上展示了光子晶体中物质与光相互作用的几个新方面。(1)我们开发了一种基于小群速度的2D光子晶体激光器。(2)我们在二次谐波产生现象中表明，利用独特的光子能带结构很容易满足相位匹配条件，并且由于小群速度，信号得到增强。(3)通过观察飞秒光脉冲在光子晶体中的传播时间，我们首次阐明了群速度比真空中的群速度小近两个数量级。

1. We have successfully fabricated three-types of two-dimensional (2D) photonic-crystal slabs or quasi-three dimensional ones from Al_xGa_<1-x> As by using the state-of-art semiconductor micro-machining technique. Then, we have charified optical responses of those samples, such as the transmittance spectrum and reflectance at specific wavelengths observed using a femtosecond light pulse. Thus, we have characterized, from the vewpoint of controlling the radiation field and light propagation, those samples with the help of the corresponding photonic band-structure calculated.(1) Optical-waveguide slab perforated periodically down to midway the lower cladding-layer ; it is clarifed that although no guided modes exist, the samples with an air-filling factor smaller than 0.3 and the number of air-hole's row smaller than 10 should work for the above purpose.(2) Air-bridge slab without any cladding-layer ; it is found that the guided modes exist, where the transmittance is almost 100%, and that this type of sample is superior.(3) Slab with the lower cladding-layer oxidized for reducing the refractive index ; this type of sample is also found to be good, since the guided modes exist in a limited energy region.2. We have experimentally demonstrated a few novel aspects of interaction between matter and light in a photonic crystal, by utilizing either a slab sample described above or a 2D capillary-type of air-rod crystal made of PbO fibers.(1) We have developed a 2D photonio-crystal laser, which is based on a small group-velocity(2) We have shown in the second-harmonic generation phenomenon that a phase-matching condition is easily fulfilled with use of a unique photonic band-structure, and that the signal is enhanced due to a small group-velocity.(3) By observing propagation time of a femtosecond light pulse through a photonic crystal, we have for the first time clarified that the group-velocity becomes smaller by almost two orders of magnitude than that in vacuum.