光学学报, 2006, 26 (9): 1409, 网络出版: 2006-09-14
波状结构二维光子晶体近场亚波长成像的研究
NearField Subwavelength Imaging in WaveLike TwoDimensional Photonic Crystal
光电子学 光子晶体 时域有限差分 负折射 亚波长成像 optoelectronics photonic crystal finitedifference timedomain negative refraction subwavelength imaging
摘要
研究了波状结构二维光子晶体(2DPC)在红外波段的负折射近场成像,对其等频面进行了分析,指出波状结构二维光子晶体无法实现负折射远场成像的原因在于缺少与入射介质等频面相匹配的光子晶体圆形等频面,所用的矩形等频面使波状膜层二维光子晶体不可避免地具有各向异性特征,进而将成像限制在近场范围内。采用时域有限差分(时域有限差分)方法模拟了不同厚度的波状结构二维光子晶体近场成像效果,当厚度为两倍栅格常量时,单光源的成像分辨力为0.28λ,达到亚波长分辨效果。分辨力随着光源逐渐远离近场范围而降低,而像点的位置基本不随光源距离和光子晶体厚度的变化而改变。双光源的成像模拟进一步验证了波状结构二维光子晶体的近场亚波长成像能力,分辨力达到0.35λ,但成像质量受光子晶体厚度变化的影响较大。
Abstract
Nearfield subwavelength imaging based on negative refraction in wavelike twodimensional photonic crystals within infared band. The adopted rectangular isofrequency surface results in the inhomogereity of wavelike twodimensional photonic crystal unavoidably, so the imaging is confined in the nearfield region. For the lack of the circularshaped isofrequency surface in photonic crystal matching that of the incident medium, farfield imaging based on negative refraction is unavailable in wavelike twodimensional photonic crystal. The finitedifference timedomain method is used to simulate the nearfield imaging in wavelike twodimensional photonic crystal of different thickness. The resolution of 0.28λ is achieved for single point source when the thickness of photonic crystal is twice of lattice constant. The resolution will gradually degrade as the source moves beyond the nearfield domain. Meanwhile, the image is strongly confined in the nearfield region on the other side of photonic crystal in spite of the change of source position and photonic crystal thickness. In order to further demonstrate the subwavelength imaging ability of wavelike twodimensional photonic crystal, double sources are used. Resolution of 0.35λ is obtained, but the imaging quality depends on the thickness of photonic crystal greately.
厉以宇, 顾培夫, 李明宇, 张锦龙, 刘旭. 波状结构二维光子晶体近场亚波长成像的研究[J]. 光学学报, 2006, 26(9): 1409. 厉以宇, 顾培夫, 李明宇, 张锦龙, 刘旭. NearField Subwavelength Imaging in WaveLike TwoDimensional Photonic Crystal[J]. Acta Optica Sinica, 2006, 26(9): 1409.