Abstract: Using numerical simulation techniques, the response characteristics of metamaterials split-ring resonators (SRRs) in terahertz region are analyzed. We examine the transmission and dispersion characteristics of several SRRs and show that there are two significant resonances corresponding to electric response and magnetic response, respectively. Based on the topology optimization technique, a terahertz magnetic response of metamaterial for the goal of maximum bandwidth is performed, the results seem to imply that the SRRs structure is the most reasonable topological form for broad magnetic resonance in THz band.
Abstract: A near-infrared detecting array is developed combining photoelectric and calorimetric method together to measure CW beam profile of high energy lasers. Detailed structure and functional modules of this system are described. The system is widely sensitive to the wavelength range of 0.9~1.7μm and the power density range of W/cm2～kW/cm2. It has an effective detecting area of 22cm×22cm with a spatial resolution of 1.1cm and a temporal resolution of 20ms. Experiments show that the uncertainty of the total energy measurement is 10% and the uncertainty of the power density distribution measurement is less than 15%.The measuring system has been successfully applied in the measurement for the far-field beam of high energy lasers.
Abstract: Gold nano-island structures were fabricated on the light-illumination side of an organic solar cell device to investigate how the light scattering by localized surface plasmon resonance influences the quantum efficiency of an organic solar cell. A light beam from a solar simulator experiences multiple interaction processes with the gold nanostructures before reaching the organic active material, which may include the scattering, the reflection, and the absorption by the gold nano-islands. However, only the scattering process may partially contribute to the enhancement of the conversion efficiency. The reflection and absorption processes make the gold nanostructures act as “blockers” and prevent the light from reaching the solar cell device. Even the scattering process may not always play positive roles in improving the performance of the device. Thus, experimental studies in this work intend to find out a balance between the loss and the enhancement mechanisms, so that the efficiency of the solar cell can be improved. Our experimental results found a possibly optimized configuration of the gold nano-island structures, which leads to enhancement of the conversion efficiency of the solar cell device.
Abstract: Metallic photonic crystals (MPC) consisting of gold nanowires on a waveguide layer of indium tin oxide (ITO) has been fabricated using interference ablation. A sensor device based on this kind of waveguide MPCs is demonstrated by the measurements on the concentration change in the glucose/water solution. A special definition is formulated for the amplitude sensor signal for such a sensor device, which shows excellent linear dependence on the change in the environmental refractive index.
Abstract: In order to achieve 1~14μm infrared stealth, the forbidden band of photonic crystal (PC) must be broaden. In this paper, we systematically studied several parameters affect the forbidden bandwidth of PC, such as refractive index ratio, thickness and periodic number of two medium layers. Numeric calculation results show that the forbidden bandwidth increases with the refractive index ratio of two medium layers, and it no longer increases when the refractive index ratio is greater than six; the forbidden bandwidth comes largest when the optical thickness of two medium layers is equal to one quarter of center wavelength respectively; and the periodic number has little influence on the bandwidth. Based on these, we chose PbTe and MgF2 to design a compound PC by four photonic crystals whose center wavelengths are at 10.6μm, 4.8μm, 2.5μm and 1.06μm respectively, and obtained nearly 100% reflectance in 1~18μm waveband, which would well meet the demand of the all-infrared waveband stealth.
Abstract: Flat-top focus shaping using effect of polarization is investigated theoretically by vector diffraction theory. We demonstrate how to make a properly selected polarization component to achieve a flat-top focus in high numerical apertures optical systems, hence achieving a potential goal of beam shaping. The results show that the values of the polarization angle corresponding to different numerical apertures (NA)values for a flat-top focus and the polarization angle increases on increasing NA for achieving a flat-top focal spot, but the flat-top focal pattern will become -sensitive when NA is larger than 1. One will have to add a diffractive optical element to achieve a flat-top focal spot in NA larger than 1 system.
Abstract: A scheme to achieve 40Gb/s all-optical 3R-regeneration through cross-phase modulation and self-phase modulation is studied in this paper. The core of the scheme is to use ultra-highly nonlinear photonic crystal fiber as the Mach-Zehnder interference of one arm. Length of the photonic crystal fiber at the arm is adjusted after calculation so as to make the signal light through the arm produce nonlinear phase shift of by means of XPM effect, then mutual interference between the resulting light and the optical signal at the other arm is generated and the noise interfusing the system is eliminated to make the signal be regenerated. Furthermore, self-phase modulation effect of the fiber is applied to make further optimization of the signal, with Optisystem for simulation experiment.
Abstract: Double Rayleigh scattering (DRS) induces coherent noises in remotely interrogated optical fiber sensor systems especially when high coherence laser sources are used. Phase generation carried (PGC) technique has been used in optical fiber sensors to overcome bias induced signal fading and eliminated incoherent noises at low frequency. In this paper we demonstrated that PGC technique can also suppress DRS induced coherent noises. In an experimental setup with total 50-km input and output lead fibers, we achieved maximum 7dB of intensity noise suppression and maximum 10dB of phase noise suppression. With PGC technique, DRS induced phase noise has been suppressed to the sensor self-noise level.
Abstract: It is practically significant to develop a kind of selective absorbing coating with excellent performance and usability for flat-plate solar collector, and to work out the related preparation craft. In this article, the Cu-based SS-O solar spectrum flat-plate selective absorption coating system was prepared by the method of direct current reactive sputtering coating films, in which, two layers are SS-O absorbing layer and one is Si-O anti-reflection layer. The reflectance spectra of the absorption coating system was measured by UV3600 spectrophotometer, the reflectance and absorptance of the absorption layer and the anti-reflection layer were calculated, and certain experimental tests were conducted on the prepared absorption coating system in terms of the salt spray resistance performances. The results show that the SS-O selective absorption coating which was prepared by magnetron sputtering technique possesses excellent corrosion resistance, whose absorption rate and the emission ratio have reached the level of the German blue tape series. It can meet the domestic demand for high-level flat-plate market.
Abstract: We proposed a scheme for the generation of multi–atom W states with two-photon Jaynes-Cummings Model in ultrahigh-Q toroidal microcavities. We consider that the two modes, clockwise (CW) and counterclockwise (CCW) modes inside the microtoroidal resonator, can be produced by embedding Bragg grating in the microtoroidal.