磁光波导的折射率、吸收系数等参数的测量

本文提出用透射率谱测量波导的折射率、吸收系数等参数的测量方法，对其原理进行了分析，为测量和数据处理提供了理论依据．

基于硅基石墨烯的全光控太赫兹波强度调制系统研究

在太赫兹通信等系统中需要利用太赫兹波调制器对信号进行调制。基于Ga As等传统半导体材料设计和制作的调制器在太赫兹波段的响应过低,因而很难应用于太赫兹系统。为了弥补传统调制技术在带宽和调制深度不够的缺点,设计了一种全新的基于硅基石墨烯的全光控太赫兹强度调制系统。该调制系统利用材料中光生载流子对太赫兹波的吸收特性,通过调节照射到材料上的可见光光强来改变光生载流子浓度,从而实现对太赫兹波强度调制。从理论和实验两方面对这种新型太赫兹强度调制系统的调制深度和调制带宽进行了研究。研究结果表明,在泵浦光功率密度为18 m W/mm2时,该调制系统能在实验使用的THz-TDS测试系统（0.1~2.5 THz）的整个频谱范围内进行有效的调制,调制深度可达到12%。且随着泵浦光能量的增大,调制深度增大。

Spectral Transmittance of Di-methyl Silicon Oil as a Heat Transfer Material for Concentrator Solar Cells

The accelerated life test was carded out to investigate the change of spectral transmittance of di-methyl silicon oil and the effects on the electrical performance of silicon solar cell. The di-methyl silicon oil samples be- fore and after accelerated life test were analyzed by FT-IR, GC-MS and LC-MS. The ring compounds and linear compounds with larger molecular weight were detected. The spectral transmittance of di-methyl silicon oil de- creased because the chromophore and auxochrome of the products made a sunlight receive decrease on the surface of the solar celt, and resulted in the reduction of cell performance. According to the decrease of spectral transmit- tance of di-methyl silicon oil, two recovery methods were proposed. The results showed that extraction was supe- rior to vacuum distillation in recovering the aged di-methyl silicon oil.

High-sensitivity refractive index sensors based on fused tapered photonic crystal fiber

In this paper, a novel liquid refractive index （R/） sensor based on fused tapered photonic crystal fiber （PCF） is proposed. It is fabricated by fusing and tapering a section of PCF which is spliced with two single-mode fibers （SMFs）. Due to the fused biconical taper method, the sensor becomes longer and thinner, to make the change of the outside RI has more direct effects on the internal optical field of the PCF, which finally enhances the sensitivity of this sensor. Experimental results show that the transmission spectra of the sensor are red-shifted obviously with the increase of RI. The longer the tapered region of the sensor, the higher the sensitivity is. This sensor has the advantages of simple structure, easy fabri- cation, high performance and so on, so it has potential applications in RI measurement.

Convenient and inexpensive determination of optical constants and film thickness of blended organic thin film

This work presents the study of optical constants and film thickness of blended organic thin films, emphasizing on the modeling procedure with modified genetic algorithm aided by absorption or transmittance spectra of both pure materials and the blends. Taking the blending of copper phthalocyanine(Cu Pc) and fullerene(C60) as an example, a simple, convenient and low-cost method for the determination of the optical constants and film thickness of blended organic thin films was demonstrated. New scheme for optical modeling of blended organic thin film was proposed by introducing peak energies of Cody-Lorentz oscillators of the pure materials, which were determined by fitting the film absorption of pure materials. These oscillators of pure materials could be recognized in the transmittance spectrum of their blends, and were further used as the initial searching ranges in the simulation of blended films. As a result, the constraint bounds of the unknown parameters were significantly reduced and modeling efficiency as well as fitting accuracy was improved. For instance, the fitting of the transmittance curves of blended films with different blending ratios reached reliable results in comparison with extinction coefficients obtained from experiment.

Single-pixel imaging with neutrons

Neutron imaging is an invaluable tool for noninvasive analysis in many fields.However,neutron facilities are expensive and inconvenient to access,while portable sources are not strong enough to form even a static image within an acceptable time frame using traditional neutron imaging.Here we demonstrate a new scheme for single-pixel neutron imaging of real objects,with spatial and spectral resolutions of 100 lm and 0.4%at 1A,respectively.Low illumination down to 1000 neutron counts per frame pattern was achieved.The experimental setup is simple,inexpensive,and especially suitable for low intensity portable sources,which should greatly benefit applications in biology,material science,and industry.