An approach to distinguish eight kinds of different human cells by Raman spectroscopy was proposed and demonstrated in this paper. Original spectra of suspension cells in the frequency range of 623~1783 cm⁻¹ were acquired and pre-processed by baseline calibration, and principal component analysis (PCA) was employed to extract the useful spectral information. To develop a robust discrimination model, a linear discriminant analysis (LDA) and quadratic discriminant analysis (QDA) were attempted comparatively in the work. The results showed that the QDA model is better than the LDA model. The optimal QDA model was generated with 12 principal components. The classification rates are 100% in the calibration and prediction set, respectively. From the experimental results, it is concluded that Raman spectroscopy combined with appropriate discriminant analysis methods has significant potential in human cell detection.

A terahertz amplitude modulator based on graphene on a metallic square ring resonant structure is proposed. By separating the graphene and the metallic structure with a thin organic dielectric layer, both the resonant frequency and the amplitude of the transmission resonant peak are modulated when graphene is electrically tuned by a bias voltage. A maximal amplitude modulation depth of 72% at the frequency of 0.6 THz is achieved for the fabricated Terahertz modulator. An analysis model based on the transmission line theory is built to explore the modulation mechanism. Results of the transmission spectrum and the amplitude modulation indicate a good agreement between the transmission line theoretical predictions and the experimental measurements.

A terahertz modulation structure based on hybrid metamaterial and graphene is proposed and demonstrated in this work. The metamaterial with a square slit ring array excites terahertz resonance in the slits and enhances the interaction between the terahertz wave and graphene. The graphene layer acting as the active material is tuned by the applied electrical field. With the separation by a dielectric layer between the graphene and the metallic structure, the resonant frequency and transmitted energy are both modulated by the graphene. Experimental result indicates that the modulation depth of the terahertz transmitted amplitude is 65.1% when the applied modulation voltage is tuned 5 V.