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Method for extracting material optical constant by using terahertz spectral signal

A signal extraction and optical constant technology, applied in the field of optoelectronics and materials science, can solve the problem of uncertainty limitation of the measured signal

Active Publication Date: 2014-03-19
DONGGUAN UNIV OF TECH
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Problems solved by technology

There are several problems in the existing method of extracting optical constants of materials by using terahertz spectral signals: first, a weak absorption approximation (n>>κ); second, there are certain boundary constraints on the tested materials, such as Higher refractive index and / or thicker samples; third, the accuracy of these algorithms is also limited by the uncertainty of the measured signal

Method used

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  • Method for extracting material optical constant by using terahertz spectral signal
  • Method for extracting material optical constant by using terahertz spectral signal
  • Method for extracting material optical constant by using terahertz spectral signal

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specific Embodiment 1

[0103] 1. Experimentally test the GaAs semiconductor sample signal and reference signal, the sample thickness is 0.63mm. Figure 4 is the measured reference signal (dashed line) and sample signal (solid line) in the time domain, Figure 5 , Image 6 are the amplitude and phase of the reference signal (dotted line) and sample signal (solid line) in the frequency domain after Fourier transform.

[0104] 2. According to the sample thickness l, the time delay Δt between the sample signal and the reference signal, and the time window size t c (time from the incidence of the reference signal to the end of the measurement), to obtain the estimated refractive index n g , the maximum reflected echo order m value and the extinction coefficient κ g .

[0105] from Figure 4 It can be seen that the amplitude and shape of the THz waveform measured before and after placing the sample change. This is because when the THz pulse passes through the sample GaAs crystal, the signal waveform ...

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Abstract

The invention belongs to the technical field of photoelectronics and material science application, and particularly relates to a method for extracting a material optical constant by using a terahertz spectral signal. The method comprises the following steps: 1, enabling a terahertz wave to vertically enter a slab sample with a thickness of 1, which is placed in air, to obtain a theoretical ratio A (Omega) of terahertz frequency spectrums of a sample signal and a reference signal according to a Fabry-Perot cavity mould; and 2, obtaining a global minimum between the theoretical ratio A (Omega) of terahertz frequency spectrums of the sample signal and the reference signal and an experiment ratio Ameas (Omega) by using a simulated annealing optimization algorithm, and obtaining an actual refractive index n (Omega) and an extinction coefficient k(Omega) which correspond to the minimum. According to the method, the material optical constant is extracted by combining the simulated annealing optimization algorithm by adopting an accurate formula, weak absorption approximation and material boundary constraints can be eliminated; and the method is suitable for materials with different thicknesses. The accuracy of the material optical constant extracted by adopting the method is high.

Description

technical field [0001] The invention belongs to the technical field of optoelectronics and material science applications, and in particular relates to a method for extracting material optical constants by using terahertz spectral signals. Background technique [0002] At present, various spectroscopic techniques have been widely used in material analysis, and the method of extracting material optical constants by using terahertz spectral signals has become a common method in the professional field. The optical path of the existing terahertz time-domain spectroscopy system is as follows: figure 1 As shown, the system is used to measure the terahertz spectra of the sample transmitted signal and the reference signal. The commonly used steps to extract the optical constants of materials are as follows: [0003] 1. The terahertz spectrum of the sample signal and the reference signal is measured through experiments, and the comparison between the two is expressed as: [0004] A...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N21/3586
Inventor 凌东雄王红成黄晓园
Owner DONGGUAN UNIV OF TECH
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