The terahertz monolithic integrated device is to integrate the pumping area of the terahertz generation, the detection area of the terahertz receiving and the metal waveguide of terahertz transmission on the same substrate. The terahertz generation and detection device use a photoconductive antenna structure,the metal waveguide use a microstrip line structure. The evanescent terahertz-bandwidth electric field extending above the terahertz transmission line interacts with, and is modified by, overlaid dielectric samples, thus enabling the characteristic vibrational absorption resonances in the sample to be probed. In this device structure, since the semiconductor substrate of the photoconductive antenna is located between the strip conductor and the dielectric layer of the microstrip line, and the semiconductor substrate cannot grow on the dielectric layer directly. So how to prepare the semiconductor substrate of the photoconductive antenna and how to bond the semiconductor substrate to the dielectric layer of the microstrip line is a key step in the terahertz monolithic integrated device. In order to solve this critical problem, the epitaxial wafer structure of the two semiconductor substrates is given and transferred to the desired substrate by two methods, respectively.
The light field includes the direction information and location information. Light field imaging can capture the whole light field by single exposure. The four-dimensional light field function model represented by two-plane parameter, which is proposed by Levoy, is adopted in the light field. Acquisition of light field is based on the microlens array, camera array and the mask. We calculate the dates of light-field to synthetize light field image. The processing techniques of light field data include technology of refocusing rendering, technology of synthetic aperture and technology of microscopic imaging. Introducing the technology of light field imaging into THz, the efficiency of 3D imaging is higher than that of conventional THz 3D imaging technology. The advantages compared with visible light field imaging include large depth of field, wide dynamic range and true three-dimensional. It has broad application prospects.
Since many vibrations and rotational levels of biomolecules fall within the THz band, THz spectroscopy can be used to identify biological samples. In addition, most biomolecules need to maintain their biological activity in a liquid environment, but water as polar substance has strong absorption to the THz wave. Thus, it is difficult to detect the sample information in aqueous solution using THz wave. In order to prevent the information of biological samples were masked in the solution, many research methods were used to explore how to reduce the water absorption of terahertz. In this paper, we have developed a real-time chemical methodology through transmission Terahertz time-domain spectroscopy (THz-TDS) system. The material of Zeonor 1020r is used as substrate and cover plate, and PDMS as channel interlayer. The transmission of the empty microfluidic chip is more than 80% in the range of 0.2-2.6 THz by THz-TDS system. Then, experiments were carried out using chips, which were filled with different volumes of 1, 2- propanediol, and it has been proved that the microfluidic chip could reduce the water absorption of terahertz. Finally, in order to further explore the reduction of terahertz to water absorption, we inject different concentrations of electrolyte to the chip. The results show that with the addition of different electrolytes, terahertz transmission line has evident changes. It can be taken into account that the electrolyte has different effects about the hydrogen bonds in the aqueous solution. Some of them can promote water molecules clusters, while others destroy them. Based on the basis of microfluidic chip, the discovery of this phenomenon can provide a way that reduces water absorption of terahertz. This work has laid a solid foundation for the subsequent study in reducing water absorption of terahertz.
Microfluidic technology can control the fluidic thickness accurately in less than 100 micrometers. So the combination of terahertz (THz) and microfluidic technology becomes one of the most interesting directions towards biological detection. We designed microfluidic chips for terahertz spectroscopy of biological samples in aqueous solutions. Using the terahertz time-domain spectroscopy (THz-TDS) system, we experimentally measured the transmittance of the chips and the THz absorption spectra of L-threonine and L-arginine, respectively. The results indicated the feasibility of performing high sensitivity THz spectroscopy of amino acids solutions. Therefore, the microfluidic chips can realize real-time and label-free measurement for biochemistry samples in THz-TDS system.
Many Biomolecules vibration frequencies are in terahertz (0.1THz-10THz) frequency range, so terahertz (THz) technology is an essential tool for detecting biological molecules. However, due to terahertz strongly absorbed by water, it is difficult to detect these molecules for biological and chemical liquid samples. Therefore, we present a novel detection method by combining terahertz technology with microfluidic technology. The strong absorption of water is effectively overcome by controlling the length that terahertz passes through liquid samples. What’s more, a higher signal to noise ratio is obtained through using less samples. In this paper, we designed a THz microfluidic chip that is easy to be fabricated by using the materials of Zeonor and polydimethylsiloxane (PDMS). Using terahertz time-domainspectroscopy (THz-TDS) system, we find that the chip has a high transmittance above 80% in the range from 0.2 THz to 2.6 THz. Then the THz spectra of deionized water and different kinds of solutions with different concentrations in the microfluidic chip were measured, respectively. In our research, it is found that different kinds of solutions have different transmission coefficients for THz. In addition, the THz transmission and absorption spectrum changes with the concentration of the same kind of solution.
Waveguides, which can transmit high frequency electromagnetic waves, have a lot of types, such as microstrip line (MSL), coplanar waveguides (CPW), coplanar-strip-line (CPS) and so forth. In the waveguides mentioned above, CPW has the advantages of easy fabrication and superior performance. Meanwhile MSL also has many advantages such as small size, light weight and high spectral resolution, but it also shows a higher attenuation and dispersion compared with the free-space waveguides. So in on-chip terahertz system, CPW and MSL was used as waveguides to transmit terahertz waves and the HFSS software was used to simulate and analyze the transmission characteristics of the MSL and CPW based on the on-chip system researched by University of Leeds (America) and Hiroshima University (Japan). The simulation results show that the scattering parameters of the two waveguides are similar to the known literatures. Meanwhile we also have designed a new structure of MSL which is applicable for our on-chip system.
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