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Terahertz is a relatively new, and yet to be explored that how it interacts with many biological objects like avian eggshell. Eggshell protects internal contents of egg from contaminants and ultraviolet radiation. It also acts as a major mineral source for embryonic development. The refractive index indicating eggshell compactness could be a potential quality criterion of shell for both table and hatching egg. But a little is known about refractive index of eggshell. However, the available information is only based on destructive method which is not suitable to use in many cases due to loss of eggshell integrity. Therefore, we aim to develop a non-destructive protocol of eggshell refractive index measurement using terahertz timedomain spectroscopy (THz-TDS) which can directly derive refractive index in the terahertz region from the temporal pulses. In order to get rid of intense terahertz absorption by egg albumen, we used THz-TDS to measure reflectance of intact eggshell in the 0.2-1.2 THz. THz wave`s frequency domain interferences signal contains the information of both thickness and refractive index of the eggshell. The results revealed that this proposed method can be used in estimation of refractive index of intact eggshell with co-efficient of determination (R2) of 0.49. This non-destructive protocol could not only be used in industrial grading of eggs but also in many applied research fields such as applied optics, ornithology, evolutionary biology in the future.
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