In this paper, a polarization filter based on photonic crystal fiber (PCF) with nanoscale gold film is proposed and analyzed theoretically. The cross-section of the structure is composed of four-layer air holes with a hexagonal lattice and two symmetrical air holes in the sub-internal layer are coated with gold film. We research that the PCF structure parameters affect the performances of the polarization filter through employing the finite element method. It is indicated by the numerical results that the resonance strength in y-polarization direction can reach a most value of 272.8 dB/cm at the communication wavelength of 1.55 μm. The extinction ratio can be better than 20 dB within a wavelength range from 1.45 μm to 1.75 μm when the length of the PCF is longer than 500μm. Therefore, such a length can make the communication filtering effect be realized using a shorter fiber. The calculated results can provide some references to the design of polarization micro-filter devices.
Based on the influence of surface metal materials on electric field, a terahertz metamaterial absorber with a highly symmetrical open box was designed. Aiming at the traditional square ring absorber, the absorber is made of three open square rings and a pair of symmetrical strips of silicon. Starting from the structure and material of the absorber, the absorption rate of the absorber to the three-frequency band wave is regulated by changing the size of the surface metal ring, changing the thickness of the dielectric layer, changing the dielectric constant of the dielectric layer material, and adjusting the conductivity of the silicon material after the addition of semiconductor silicon. When no semiconductor silicon is added, the absorption rate of the absorber in the low frequency band reaches 94.77% and the absorption frequency band is 0.73thz. By increasing the thickness of dielectric layer, the phenomenon of redshift is obvious, which can realize the purpose of continuous frequency band absorption. By adding the silicon strip with symmetrical structure and changing the conductivity comparison, it is found that it can close the absorption peak in the high frequency band, reducing the absorption rate to less than %, and at the same time affecting the absorption rate of the low frequency band.
Real-time detection for living cells in vitro is essential for cell physiology, leading to a strong requirement of low cost and label free biosensors. At present, the terahertz plasmonic metamaterials (TPMMs) are an especially attractive application for biosensing owing to their sharp resonances respond. Compared with traditional biosensors, such as flow cytomertry, the TPMMs biosensors have many unique advantages, containing real-time monitoring, free label and high sensitivity. In this paper, we proposed a TPMMs which is designed by digging out periodically arranged regular hexagonal holes on the metal plate with the thickness of 200 nm. The samples of the TPMMs is used as a platform for detecting liver cancer cell GEP2 concentration at five levels (1 × 104, 5 × 104, 1 × 105, 3 × 105 and 5 × 105cells/ml). The results show that The THz PMMs biosensor cannot distinguish cell concentrations within the orders of magnitude between 1 × 104 and 5 × 104 cells/ml, however, it can distinguish cell concentrations within the orders of magnitude between 1 × 104 and 1 × 105 cells/ml based on the x-polarized reflection spectrum TPMMs biosensor. On the other hand, the transmission spectrum TPMMs biosensor has a significant detectability of the orders of magnitude cell concentration between 104 and 105 cells/ml. The proposed TPMMs biosensor paves a fascinating platform for have been widely applied for cell detection, biotechnology.
The rapid detection of cancer cells is crucial for clinical diagnosis in biomedical field. The traditional flow cytometry (FC) in visible band, a fluorescence-labelling detection, gives rise to the complicated sample preparation and the irrecoverable antibody consumption; it blocks the development toward a convenient detection platform with fast, inexpensive and non-labelling. Here, a specifically designed metamaterial based on split ring resonators (SRRs) is proposed. Such metamaterial operating in terahertz (THz) range exhibits polarization-dependent resonances, which are observed both in experiments and simulations. Additionally, the biosensing property of the metamaterial is investigated. On metamaterial surfaces, the lung cancer cells A549 are cultured. Under the irradiation of x-polarized THz waves, it is found that for the cell concentrations from 1×105 cells/ml to 5×105 cells/ml, the maximum frequency shift Δf (the frequency difference between measured sample and bare one) at 2.24 THz increases from 15 GHz to 137 GHz, respectively. Such results also imply that a larger cell concentration leads to a higher frequency shift. Subsequently, the samples are further measured at different polarization angles. The results show that for cell concentration of 5×105 cells/ml, the Δf exhibits the same value of 130 GHz when polarization angle equals 30° and 150°, and 15 GHz when polarization angle equals 60° and 120°. Our proposed metamaterial may supply a potential biosensing method for the detection of cancer cells, exhibiting a new insight toward the cancer cell biosensing with certain information of polarization response.