Myelin Sheath as a Dielectric Waveguide for Signal Propagation in the Mid‐Infrared to Terahertz Spectral Range

Abstract The myelin sheath enables dramatic speed enhancement for signal propagation in nerves. In this work, myelinated nerve structure is experimentally and theoretically studied using synchrotron‐radiation‐based Fourier‐transform infrared microspectroscopy. It is found that, with a certain mid‐infrared to terahertz spectral range, the myelin sheath possesses a ≈2‐fold higher refraction index compared to the outer medium or the inner axon, suggesting that myelin can serve as an infrared dielectric waveguide. By calculating the correlation between the material characteristics of myelin and the radical energy distribution in myelinated nerves, it is demonstrated that the sheath, with a normal thickness (≈2 µm) and dielectric constant in nature, can confine the infrared field energy within the sheath and enable the propagation of an infrared…