Analyzing terahertz time-domain transmission spectra with multi-beam interference principle

We present a data processing method based on multiple beam interference and Fresnel's formula that extract simultaneously the refraction index and the extinction coefficient from terahertz time domain spectra, and the dielectric coefficient can also be calculated. Typical THz-TDS system working in transmission mode was utilized for direct measurement of the transmission spectra with a frequency accuracy of 7.6 GHz and range from 0.3 THz to 4 THz at room temperature. This method is verified with a double-faced polished 350-μm 100-cut GaAs wafer, and the reasonable average relative error for refractive index in the whole range is less than 0.83% comparing with conventional method, which provides a new approach to process the transmission spectra with oscillations.

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