Detecting the propagation effect of terahertz wave inside the two-color femtosecond laser filament in the air

Zhao, Jiayu; Zhang, X.; Li, S.; Liu, C.; Chen, Y.; Peng, Yan; Zhu, Yiming

doi:10.1007/s00340-018-6913-1

Cited by 4 publications

(3 citation statements)

References 29 publications

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“…This result can be seen from the radial distributions of THz intensity at 0.4, 0.5, 0.6, 0.7 and 0.8 THz in figure 7(c), calculated based on the N e (r) data in figure 7(b) and the previously reported 1DND model [31,32]. This offaxis THz mode (in ring shape) is also known as the result of the spatial confinement of THz wave inside the filament [29,31,32,44,45], namely, a unique experimental phenomenon that the THz energy is spatially constrained inside a space which is much smaller than the THz wavelength.…”

Section: Numerically Simulated Off-axis Thz Mode Field Inside the Fil...supporting

confidence: 54%

“…The dashed lines have highlighted this tendency by marking the peaks of the THz waveforms at each z, and the horizontal solid line is for contrast. As demonstrated in [29,44], this temporal advance of the THz transient is a good indicator of THz wave propagation inside the plasma column, during which the THz refractive index is below the unity and thus the THz pulse has a superluminal phase velocity.…”

Section: Evidences Of Thz Wave Propagation Inside the Filamentmentioning

confidence: 85%

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Investigating the non-radially polarized component of terahertz wave emission during single-colour femtosecond laser filamentation in air

Zhao

Gao

et al. 2018

J. Opt.

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Recently, simultaneous emission of radially and non-radially polarized terahertz (THz) pulses during single-colour femtosecond laser filamentation has been reported. In this work, the latter radiation has been specifically investigated, instead of the well-studied THz radial polarization. Briefly, cut-back measurements have verified that the ellipticity of the generated THz pulse with non-radial polarization decreased (became more linearly polarized) with the increasing filament length. The underlying mechanism responsible for this phenomenon is the existence of a propagation effect of THz wave along the filament plasma channel. In this case, the resulted off-axis propagation of THz wave inside the plasma column played a dominant role on the generated non-radial THz polarization, rather than the expected on-axis THz birefringence induced by the high laser intensity. This discovery will greatly renew the understanding of THz emission from plasma sources.

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Section: Numerically Simulated Off-axis Thz Mode Field Inside the Fil...supporting

confidence: 54%

Section: Evidences Of Thz Wave Propagation Inside the Filamentmentioning

confidence: 85%

Investigating the non-radially polarized component of terahertz wave emission during single-colour femtosecond laser filamentation in air

Zhao

Gao

et al. 2018

J. Opt.

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“…According to the method for determination of the density of wood (ISO 3131 (1975)), the wood samples were placed in a drying box and dried at 103 ± 2 ℃ for 8 h (Zhao et al 2018). Then, an electronic balance with accuracy of 0.001 g was used to weigh the quality.…”

Section: Standard Moisture Content Determination Methodsmentioning

confidence: 99%

Prediction of wood moisture content based on THz time-domain spectroscopy

Duan

Wang

Жао

et al. 2022

BioRes

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A new method for predicting wood moisture content using terahertz (THz) time-domain spectroscopy (TDS) is presented in this paper. The THz wave is a promising method in measuring wood moisture content due to its sensitivity to water, impressive penetration ability in wood, and no destructive effect on wood interior. In this study, the selected wood, Douglas fir (Pseudotsuga menziesii), with different moisture content was studied. THz-TDS was used to extract the optical parameter of the sample. The THz refractive index and absorption coefficient spectrum of the wood were calculated. The first and second derivatives of the absorption coefficient spectrum were processed to obtain the first and second derivative spectra. The successive projections algorithm (SPA) was used to select the characteristic frequency for the THz absorption coefficient spectrum and its first and second derivative spectrum of the wood. A regression prediction model of wood moisture content was established by partial least squares regression (PLS). The results showed that the proposed model based on the second derivative spectrum had the best prediction effect for the moisture content of wood.

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Recording the angular dispersion of a terahertz beam into its frequency spectrum for fast measurements

Han¹,

Zhao²,

Wang³

et al. 2023

Opt. Express

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The frequency-dependent divergence angle of terahertz (THz) beams is a crucial aspect in understanding the generation and transmission of broadband THz waves. However, traditional beam profiling methods, such as 1D or 2D translation/rotation scanning detection, are time-consuming and wasteful of THz energy, making them unsuitable for fast measurement applications, such as single-shot THz generation and detection. Here, we proposed a simple solution that involves passing the THz beam through a core-anti-resonant reflective (CARR) cavity (e.g., a paper tube). The spatial information of the beam is then recorded into its frequency spectrum, which can be easily detected by a following traditional THz time-domain spectroscopy (TDS) system or a single-shot sampling setup. Our method enables the acquisition of the angular dispersion without repetitive measurements, and represents a significant step forward in fast and efficient achievement of spatial properties of broadband THz beams.

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Detecting the propagation effect of terahertz wave inside the two-color femtosecond laser filament in the air

Cited by 4 publications

References 29 publications

Investigating the non-radially polarized component of terahertz wave emission during single-colour femtosecond laser filamentation in air

Investigating the non-radially polarized component of terahertz wave emission during single-colour femtosecond laser filamentation in air

Prediction of wood moisture content based on THz time-domain spectroscopy

Recording the angular dispersion of a terahertz beam into its frequency spectrum for fast measurements

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