Optimization of light transmission efficiency for nano-grating assisted MSM-PDs by varying physical parameters

Metal–semiconductor–metal photodetectors (MSM-PDs) are utilized for suitable nano-structured fabrications that can play an important role for the development of future high-speed devices to achieve very high responsivity–bandwidth characteristics. Finite-difference time-domain (FDTD) method is used to calculate the light absorption enhancement factor of nano-grating assisted MSM-PDs near the design wavelength by changing the detector's geometrical parameters in comparison with a conventional device (i.e., without the nano-gratings). The substrates containing the aperture and the nano-gratings are optimized in thickness to trigger an extraordinary optical transmission. Besides, this paper demonstrates how the coupling condition satisfies the oscillating charge densities evolution to the surface plasmon polaritons under illumination of a polarized light and the existence of a band gap in the dispersion curve of surface plasmons propagating on periodically corrugated surfaces. The simulated results confirm that the light absorption enhancement factor of nano-grating assisted MSM-PDs is ∼12-times better than the conventional type of MSM-PDs.     

金属-介质光栅结构表面等离子体耦合效率的模拟研究

表面等离子体可以将光子局域在金属表面附近, 并形成很强的近场能量密度, 可以大大提高金属表面附近分子的发光效率和光电转换吸收材料的利用率, 从而提高发光器件和光电转换器件的效率. 本文研究了在一维周期性金属-介质混合结构的光栅中表面等离子体激元的耦合条件, 给出了耦合效率随着结构和填充因子的变化, 并证明了在光栅的填充因子较高以至光栅的金属间隔较小时, 光子耦合成为表面等离子体的效率较高, 可以达到94%以上. 关键词： 表面等离子体激元 填充因子 光栅 吸收光谱     

内嵌矩形腔楔形金属狭缝的增强透射

金属薄膜上亚波长金属狭缝的非共振光增强透射对宽频带光子器件的设计具有重要意义. 为增强金属狭缝的光透射, 设计了内嵌矩形腔楔形金属狭缝阵列, 并用有限元方法研究了该结构的透射特性. 结果表明, 内嵌矩形腔的楔形金属狭缝阵列比无矩形腔的楔形金属狭缝阵列透射率高. 此外, 还研究了矩形腔的结构参数和位置对内嵌矩形腔楔形金属狭缝阵列透射特性的影响. 这些结果将对设计具有更高透射能力的金属狭缝具有一定的指导意义. 关键词： 光异常透射 金属狭缝 表面等离极化激元     

极化激元系统时间演化的量子涨落特性和非经典统计行为

将极化激元系统约化成模型单模光子-TO声子有效相互作用系统， 在此基础上以解析形式讨论了系统的力学量、压缩态、量子涨落特性以及亚泊松分布等非经典效应的动力学演化行为.结果表明，光子场与极化波量子场彼此交换能量过程随时间演化呈振荡性质，光子场和声子场都可以演化成压缩态，其二阶压缩度随时间演化成复杂周期振荡特性，这种非经典特性是非线性相互作用的结果并且以k₁项和k₂项同时存在并相互关联为前提.而此时光子和声子统计分布随时间演化呈现介于超Poison分布和亚Poison分布之间复杂周期振荡的新结果，非线性作用k₁项和k₂项对这种非经典统计行为都有贡献. 关键词： 极化激元系统动力学演化 单模光场-TO声子有效模型哈密顿量 量子涨落与压缩态 亚泊松分布     

Non‐Radiative Energy Transfer Mediated by Hybrid Light‐Matter States

We present direct evidence of enhanced non‐radiative energy transfer between two J‐aggregated cyanine dyes strongly coupled to the vacuum field of a cavity. Excitation spectroscopy and femtosecond pump–probe measurements show that the energy transfer is highly efficient when both the donor and acceptor form light‐matter hybrid states with the vacuum field. The rate of energy transfer is increased by a factor of seven under those conditions as compared to the normal situation outside the cavity, with a corresponding effect on the energy transfer efficiency. The delocalized hybrid states connect the donor and acceptor molecules and clearly play the role of a bridge to enhance the rate of energy transfer. This finding has fundamental implications for coherent energy transport and light‐energy harvesting.     

Exciton-polariton state in nanocrystalline SiC films

We studied the features of optical absorption in the films of nanocrystalline SiC (nc-SiC) obtained on the sapphire substrates by the method of direct ion deposition. The optical absorption spectra of the films with a thickness less than ~500 nm contain a maximum which position and intensity depend on the structure and thickness of the nc-SiC films. The most intense peak at 2.36 eV is observed in the nc-SiC film with predominant 3C-SiC polytype structure and a thickness of 392 nm. Proposed is a resonance absorption model based on excitation of exciton polaritons in a microcavity. In the latter, under the conditions of resonance, there occurs strong interaction between photon modes of light with λ_ph=521 nm and exciton of the 3С polytype with an excitation energy of 2.36 eV that results in the formation of polariton. A mismatch of the frequencies of photon modes of the cavity and exciton explains the dependence of the maximum of the optical absorption on the film thickness.     

利用蛾眼结构提高有机太阳能电池光吸收效率的理论研究

为提高有机太阳能电池(OSCs)的能量转换效率,将蛾眼微结构应用于OSCs上.通过理论模拟计算,得出在有机层厚度一定的情况下,带有蛾眼微结构的OSCs相比于普通平板结构的OSCs的光吸收效率有较大的提高.通过对微结构形貌、周期和高度的优化,使蛾眼结构OSCs的光吸收效率比普通平板OSCs提高了11.3％.器件光场分布的模拟计算表明,光吸收效率的提高是由蛾眼结构减反增透的效果和表面等离子体(SPP)增强吸收共同导致的结果.     

铁电体KDP软模时间分辨的冲击受激拉曼散射

利用飞秒脉冲激光在时域内对铁电体KDP(KH2 PO4 )进行冲击受激拉曼散射 (ISRS)实验研究 ,在激发光束夹角θ=0 .38°情况下 ,发现了KDP软模与光耦合所形成的电磁耦合波子弱衰减低频振荡的冲击受激拉曼散射响应信号 ,其周期随着温度接近相变温度Tc 而逐渐增大 ,其特性可用铁电体软模在Tc 温度附近频率的变化规律ω2 =α0 (T -Tc)来描述 ,这里系数α0 ≈ 16× 10 2 0 s2 K- 1 。     

Surface plasmon polariton coupling between nano recording marks and their effect on optical read-out signal

We use the three-dimensional finite-difference time-domain method to investigate surface plasmon polariton coupling between two nano-recording marks which are of different shapes. The different coupling characteristics and the influence of these coupling effects on the read-out reflection signal will be discussed.