Research On Terahertz Spectroscopy Based On Spintronics And Sensing Techniques

Traditional terahertz emission source including nonlinear optical crystal and optical conductance antenna.With the development of the terahertz technology application,low cost,high efficiency,easy integration of terahertz source is required.Terahertz radiation based on spintronics technology uses the characteristics of ferromagnetic and non-magnetic materials to manipulate the spin current to emit terahertz wave,such as polarization manipulation,amplitude modulation,phase modulation and radiation beam manipulation.it has become a research focus in the terahertz source.Its planar structure provides conditions for integration to produce more compact and portable devices.Metamaterial is a kind of artificial electromagnetic material,which can complete the regulation of electromagnetic field with the artificially designed periodic unit structure.It is generally used as terahertz functional device,such as sensor,absorber,modulator and filter in biomedical detection,imaging,communication and other fields.Terahertz metamaterial biosensors provide an approach to labeling-free biosensing technology.However,the lack of integration technology between terahertz biosensors and terahertz transmitters hinders the popularization of high resolution near field unlabeled terahertz biosensors.Spintronic terahertz sources provide integration conditions for near-field unlabeled terahertz biosensors.Since both metamaterial terahertz sensors and spintronics terahertz sources need to be prepared on the substrate,terahertz biosensors with integrated terahertz sources can be formed by preparing metamaterial structures and ferromagnetic films on two sides of the substrate.In this Thesis,the basic theories of terahertz time-domain spectroscopy,spintronics terahertz source and metamaterial terahertz biosensor based on previous researches are firstly introduced.Then Fe/Pt thin film samples were prepared by magnetron sputtering method.The experimental results show that the bandwidth of terahertz wave emitted by Fe/Pt film is 1.314 THz.And the factors affecting the terahertz signal were analyzed,these include substrate crystal state,Fe layer thickness,focusing lens,laser incident direction,laser power.The time-domain spectrometric system based on Fe/Pt thin film terahertz source was used for sample testing,and the results were compared with the measurements from the TPS Spectra 3000 system.The transmittance and absorbance measured by the two systems are roughly the same,which indicates that the system can meet the requirements of experimental applications.Next,the ring and cross metamaterial periodic structure is designed by simulation software.Two substrates are used for ring metamaterial structures:quartz（Si O₂）and polyethylene（PE）,the resonance points of Si O₂ and PE substrates are 0.807THz and 1.005THz respectively,the FOM values are 2and 3.1 respectively in these two cases.The base of the cross structure is Si O₂,its resonance points is 0.801THz.its FOM value is 3.7.And the metamaterial is processed on the other side of Fe/Pt thin film substrate to form an integrated terahertz biosensor.The prepared integrated terahertz biosensor was used in the experiment,and the experimental results were compared with the simulation values.Due to manufacturing errors,the simulated resonance frequency point is slightly different from the experimental resonance point.Finally,the sensor was used to measure water,alcohol and olive oil.Due to the different dielectric properties of the three liquids,the offset of the resonant frequency point is also different.These results provide a reference for the application of integrated terahertz devices in unlabeled sensing detection in the field of biochemistry.