Terahertz-wave generation in silica nanofibers

This paper investigates the generation of terahertz (THz) waves in silica nanofibers through the difference frequency generation (DFG) process, incorporating surface-emitted modal phase-matching. This nonlinear process uses both surface dipole and bulk multipole nonlinearities. The adoption of a surface-emitted configuration serves to mitigate absorption losses within the THz range by initiating THz wave generation from the silica nanofiber’s surface. Theoretical analysis suggests that a silica nanofiber can generate a surface-emitted THz-wave using two guided modes: the TE[Formula: see text] mode at a wavelength of 780nm and the TM[Formula: see text] mode at a wavelength ranging from 750nm to 780nm, resulting in a difference frequency within the THz range from 1THz to 15THz. Utilizing coupled-wave theory, we derive the power expression for the generated THz-wave. These calculations are based on the assumption of two pump powers of 1 W each. An optimized architecture utilizing a silica nanofiber with a length of 200[Formula: see text]m coated with a 20nm thick nonlinear Bismuth Selenide (Bi 2 Se 3 ) coating can achieve up to [Formula: see text] W[Formula: see text] of power-normalized conversion efficiency, in contrast to the estimated 10[Formula: see text] W[Formula: see text] for a bare silica nanofiber of the same length. This work contributes to advancing the understanding of THz-wave generation in optical nanofibers, with potential applications in various fields such as THz sensors and wireless communication.