Dongwei Zhai

Dongwei Zhai
  • Doctor of physics
  • Professor (Assistant) at Qingdao University

About

18
Publications
1,803
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97
Citations
Introduction
optical-pump/THz generation, nano-thin material characterization, carrier dynamics, THz generation, nonlinear optics
Skills and Expertise
Current institution
Qingdao University
Current position
  • Professor (Assistant)

Publications

Publications (18)
Article
Full-text available
We report on the generation of THz waves through optical rectification in ZnTe of femtosecond laser pulses whose photon energy is tuned from below to above the ZnTe bandgap energy. The THz signal exhibits a pronounced peak at the bandgap energy, at THz frequencies for which losses in ZnTe remain small. This peak is likely due to the resonance of th...
Article
Full-text available
By generating terahertz pulses in KTP crystals through optical rectification with a pump photon energy varying from below to above the bandgap, we observe a peak of the THz signal at the bandgap energy but also a second one around half the bandgap. This later one is attributed to a two-photon absorption enhanced nonlinearity, which is validated by...
Article
Full-text available
The surface velocity and the bulk lifetime of photo-excited free carriers in GaAs were measured using an optical-pump and THz-probe time-domain technique. By varying the pump laser photon energy from 1.56 to 4.15 eV, we observe that the surface velocity drops abruptly from 0.7 × 10 6 cm/s down to 0.2 × 10 6 cm/s at 2.5 eV, while the bulk lifetime r...
Article
Full-text available
We study optical rectification in GaSe by performing THz generation with femtosecond laser pulses whose wavelength is tuned from below to above the GaSe bandgap. As expected from a theory, we observed a first THz emission peak at 1.77 eV, where phase matching is realized. A second THz emission peak was recorded, when the pump photon energy reaches...
Article
Full-text available
The rapid advancement of terahertz (THz) technology has driven an increasing demand for efficient THz sources and detectors, particularly in applications such as spectroscopy, imaging, and wireless communications. Organic (NLO) crystals, renowned for their high nonlinear coefficients, tunability, and flexible molecular design, have emerged as highl...
Article
Full-text available
In this paper, we study terahertz generation through optical rectification in reflection at normal incidence in a dielectric nonlinear crystal. We first analyze, with a nonlinear optical model, the sample parameters (thickness, absorption at both laser and terahertz wavelengths, etc.) for which a terahertz optical rectification reflection scheme is...
Article
We investigate terahertz time-domain spectroscopy (THz-TDS) as a non-destructive and non-contact technique for depth profiling of dopants in semiconductors. THz temporal waveforms transmitted through silicon-ion-implanted semi-insulating gallium arsenide substrates, as-implanted or post-annealed by rapid thermal annealing, were analyzed by assuming...
Conference Paper
Full-text available
In this work, we demonstrate a high-selectivity terahertz (THz) band-stop filter with a wide range of center wavelengths (CWLs) from 150 to 600 m (2.0 THz to 0.5 THz). The dip transmission is lower than 10 % at the center CWLs, even to 5 % at 1.9 THz. The band-stop terahertz filter is based on periodic metallic Cross Cell (CC) structures deposited...
Article
Full-text available
Nondestructive analysis of historical objects is of significance for cultural heritage conservation. In this paper, terahertz time-domain spectroscopy (THz-TDS) was used to distinguish seven red mineral pigments used in ancient Chinese artworks. Two absorption features of natural minerals HgS and four highly resolved spectral features of mineral pi...

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