Development of Photonic Crystals for Radiation-Field Control

1.我们利用先进的半导体微加工技术成功地制备了三种类型的Al_xGa_ As二维或准三维光子晶体<1-x>。然后，我们描述了这些样品的光学响应，例如使用飞秒光脉冲观察到的特定波长的透射光谱和反射光谱。因此，我们从控制辐射场和光传播的角度，借助于计算出的相应的光子带结构，对这些样品进行了表征。(1)光波导板周期性穿孔到下包层的中部，阐明了虽然不存在导模，但空气填充因子小于0.3，空气孔排数小于10的样品可以达到上述目的。(2)无包层的空气桥平板，发现导模存在，透射率接近100%，是一种上级的样品。(3)下包层氧化降低折射率的平板，这种类型的样品也被发现是好的，因为导模存在于有限的能量区域.我们已经通过实验证明了光子晶体中物质与光之间相互作用的一些新方面，通过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。(1)我们已经研制出了一种基于小群速度的二维光子晶体激光器。（2）我们已经在二次谐波产生现象中表明，使用独特的光子带结构可以容易地满足相位匹配条件，并且由于小的群速度，信号被增强。(3)通过对飞秒光脉冲在光子晶体中传播时间的观测，我们首次阐明了飞秒光脉冲在光子晶体中的群速度比在真空中的群速度减小了近两个数量级。

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.