Study on terahertz time domain spectroscopy of pine wood nematode disease

Pulsed terahertz time domain spectroscopy (THz-TDS) is a coherent technique, in which both the amplitude and the phase of a THz pulse are measured. Coherent detection enables direct calculations of both the imaginary and the real parts of the refractive index without using the Kramers-Kronig relations. In this paper, the spectroscopic characteristics of pine wood nematode and diseased pine wood in the THz regime are studied. In order to look for a rapid spectroscopic discrimination method for the disease, we measure the transmission characteristics of a Bursaphelenchus xylophilus (Bx) sample and a Bursaphelenchus mucronatus (Bm) sample by terahertz time domain spectroscopy. The measured time domain spectrums and corresponding frequency domain spectrums are compared to distinguish them from their absorption characteristics. At the same time, we also measure the transmission characteristics of a healthy Pinus massoniana (Pm) wood sample, a Pm with Bm wood sample, and a diseased Pm wood sample by THz-TDS and compare their difference in THz absorption spectrum and diffraction dispersive spectrum to confirm the effect of Bx on Pm by the absorption coefficient and refractive index.