The presence of random scattering layers diffuses incident field information of objects, which interferes with the imaging process of objects, resulting in the geometry of objects not being accurately imaged. In this paper, we propose and experimentally demonstrate an approach for computational imaging of moving hidden objects through random scattering layers based on speckle cross-correlation method. Theoretical analysis denotes that imaging of moving objects is achieved by the speckle cross-correlation function and the conventional Fienup-type iterative phase-retrieval algorithm. The proposed results may have applications in imaging through grove and biological tissues.
We have used Terahertz time-domain spectroscopy(TDS) to investigate the dielectric properties of water and water solutions of containing different ions. The complex permittivity of NaCl solutions, for different concentrations of ions, was obtained by attenuated total reflection(ATR) method. We have observed that, when increasing o ion concentration, the real part and imaginary part of the permittivity are increased. Furthermore, we also calculate the dielectric constant of ionic aqueous solutions with different concentrations based on molecular dynamics method. The simulation method, based on Newton mechanics, can estimate the dielectric constant of liquid substances without the experimental limitation.
A novel nested anti-resonant hollow core fiber (NAHF), based on Topas, with low loss and flattened dispersion is proposed for efficient transmission of terahertz wave. Finite element method with an ideally matched layer (PML) boundary condition is used to investigate its guiding properties. A cladding structure of nested anti-resonant elliptical rings is introduced to reduce mode power leakage. The NAHF shows a low confinement loss (< 0.29 cm-1 ) and a small effective material loss (< 0.019 cm-1 ) in the frequency range of 0.9-1.5 THz. An ultra-flatted near zero dispersion profile of ±0.029 ps/THz/cm is obtained within a broad frequency range of 0.6-1.5 THz. Furthermore, optimizing the structure parameters in NAHF, higher core power fraction over 80 %, higher effective mode area of ~10-6 μm2 and the bending loss of 3.05×10-5 cm-1 at the bending radius of 10 cm are also achieved.
We have demonstrated a high-energy and broadly tunable monochromatic terahertz (THz) source via difference frequency generation (DFG) in DAST crystal. The THz frequency is tuned randomly in the range of 0.3-19.6 THz, which is much wider than the THz source based on the inorganic crystal and the photoconductive antenna. The highest energy of 2.53μJ/pulse is obtained at 18.9 THz corresponding to the optical-to-optical conversion efficiency of 1.31×10-4. The THz output spectroscopy is theoretically and experimentally explained by DFG process and Raman spectroscopy. Meanwhile, a phenomenon of blue light from the KTP-OPO with tunable and multiple wavelengths was firstly observed and explained. Based on our THz source, an ultra-wideband THz frequency domain system (THz-FDS) with transmission mode is realized to measure the ultra-wideband THz spectroscopies of typical materials in solid and liquid states, such as Si, SiC, White PE, water, isopropyl myristate, simethicone, atonlein and oleic acid, etc.. Furthermore, we have studied the THz spectral characteristic of biomedical tissue in the ultra-wideband THz frequency range of 0.3-15THz to study the biomedical response in the entire THz frequency range, which contains more abundant spectral information and was rarely focused with the limit of the THz source.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.