Shujing Chen

Figure of Merit Enhancement of a Surface Plasmon Resonance Sensor Using a Low-Refractive-Index Porous Silica Film

In this paper; the surface plasmon resonance (SPR) sensor with a porous silica film was studied. The effect of the thickness and porosity of the porous silica film on the performance of the sensor was analyzed. The results indicated that the figure of merit (FOM) of an SPR sensor can be enhanced by using a porous silica film with a low-refractive-index. Particularly; the FOM of an SPR sensor with 40 nm thick 90% porosity porous silica film; whose refractive index is 1.04 was improved by 311% when compared with that of a traditional SPR sensor. Furthermore; it was found that the decrease in the refractive index or the increase in the thickness of the low-refractive-index porous silica film can enlarge the FOM enhancement. It is believed that the proposed SPR sensor with a low-refractive-index porous silica film will be helpful for high-performance SPR sensors development.

Design of broadband transmission quarter-wave plates for polarization control of isolated attosecond pulses

Using a standard Levenberg?Marquardt algorithm, broadband quarter-wave plates (QWPs) with bandwidth from 3 to 18 eV in the extreme ultraviolet (EUV) region were designed using aperiodic Mo/Si multilayers. By analyzing the design results of the Mo/Si multiayers with different bilayer numbers, we found that a Mo/Si multilayer with more bilayers can achieve broader phase control, but suffers from lower total throughput and a degree of circular polarization. In addition, the pulse broadenings caused by the group delay dispersions of the designed broadband QWPs were studied, and their layer distributions were investigated. The oscillating distribution of bilayer thickness in optimized multilayers was observed, which is considered to be the reason for forming the broadband phase control. Such broadband QWPs can be applied to generate a circularly polarized broadband EUV source, such as isolated attosecond pulse, directly from a linearly polarized source.

Achieving enhanced mid-infrared transmission through subwavelength periodic structures via redshift effect of the extraordinary optical transmission

The extraordinary optical transmission (EOT) phenomenon is usually more outstanding in optical and near-infrared frequency band than that in mid-infrared and other lower frequency range. In order to expand the high-quality EOT to a lower frequency, this paper proposes an effective redshift method which can cause the resonant frequencies of the EOT redshift greatly. Using this method, an EOT in mid-infrared frequency is achieved and the transmission of which is compared with that achieved via a conventional method. It is found that the peak transmission of the red-shifted EOT is enhanced greatly and can be as high as 90%, at the same time the resonance quality is preserved very well. The reason of the enhanced transmission is analyzed using the effective medium theory.

Design of broadband reflective circular polarizer for attosecond pulse in the extreme ultraviolet region

In this paper, we present a design method of broadband reflective circular polarizer (BRCP) in the extreme ultraviolet (EUV) region. By using this method, we designed three BRCPs with a 6, 12 and 18 eV bandwidth, respectively. Then, we investigated the performances of designed BRCPs in theory. The results indicated that the reflected lights of these BRCPs all showed a nearly 100% circular polarization degree and considerable circular reflection in their design band. In addition, we also studied the origin of high circular polarization degree by analyzing the phase shift and the reflectivity ratio between s- and p-polarized lights induced by the reflection of BRCPs. Furthermore, the pulse responses of BRCPs for attosecond pulses were also investigated. The proposed EUV BRCPs can be used for controlling the polarization state of broadband EUV sources, e.g., generating the circularly polarized attosecond pulse by a linearly polarized one.

Effects of dispersion and filtering induced by periodic multilayer mirrors reflection on attosecond pulses

Using temporal and spectral methods, the effects of dispersion and filtering induced by Mo/Si multilayer mirrors reflection on incident attosecond pulses were studied. First, two temporal parameters, the pulse broadening factor, and the energy loss factor, were defined to evaluate the effects of dispersion and filtering. Then, by analyzing these temporal parameters, we investigated and compared the dispersion and filtering effects on attosecond pulses. In addition, we explored the origins of pulse broadening and energy loss by analyzing the spectral and temporal characteristics of periodic Mo/Si multilayer mirrors. The results indicate that the filtering effect induced by Mo/Si multilayer mirrors reflection is the dominant reason for pulse broadening and energy loss.