Method for extracting complex refractive index of solid sheet based on terahertz reflectance spectrum

Abstract

The invention discloses a method for extracting the complex refractive index of a solid sheet based on a terahertz reflectance spectrum. The method comprises the following steps: preparing two solid sheet samples made of the same material, selecting the thin sample as a to-be-measured sample, selecting the thick sample as an auxiliary sample for time-domain signal baseline correction, and measuring the terahertz time-domain reflected signals of both the to-be-measured sample and the auxiliary sample; adopting the difference between the terahertz time-domain reflected signals of the to-be-measured sample and the auxiliary sample as a baseline, and selecting the first and second peaks of the to-be-measured sample as a baseline-corrected reference signal and a baseline-corrected sample signal respectively; conducting compound digital filtering on the baseline-corrected sample signal and the baseline-corrected reference signal separately, so as to remove system echoes and random noise; according to the filtered sample signal and the filtered reference signal, extracting the complex refractive index of the to-be-measured sample in a self-referencing manner.

Description

technical field [0001] The present application relates to the fields of photonics technology and electronics technology, and in particular to a method for extracting the complex refractive index of solid flakes based on terahertz reflection spectrum. Background technique [0002] Terahertz waves generally refer to electromagnetic radiation with a frequency in the range of 0.1 THz to 10 THz (1 THz = 1012 Hz) and a wavelength in the range of 3 mm to 30 μm. Terahertz waves are located between millimeter waves and infrared rays on the electromagnetic spectrum, and belong to the far-infrared band. The position of the terahertz frequency band in the electromagnetic spectrum is as follows: figure 1 As shown, it is the transition area between photonics technology and electronic technology, macroscopic and microcosmic. Terahertz radiation has very important scientific value, and has become a worldwide research hotspot, and is one of the most advanced fields of scientific research in...

AI Technical Summary

Problems solved by technology

[0022] This total reflection mirror reference method has the following problems: First, the transfer function The phase φ(ω) of will inevitably have a mechanical phase shift error

like figure 2 As shown in (b), it is difficult to achieve a complete reset on the surface of the sample and the surface of the total reflection mirror, and there will be an optical path difference of ΔL between the two positions

Therefore, there will be an inherent phase shift between the reference signal and the sample signal The complex refractive index of the extracted solid sheet is not accurate enough; secondly, this method requires the mechanism precision of the measurement system to be high enough, so it increases the difficulty of making the system hardware; finally, because the time domain signals of the reference and the sample need to be measured separately, Therefore, the measurement efficiency is low

Images