Terahertz generation by four-wave mixing and guidance in diatomic teflon photonic crystal fibers

Abstract

Terahertz radiation generation by four-wave mixing and low-loss propagation in a well optimized photonic crystal fiber has been presented here. Teflon with low-loss in the THz range has been considered where diatomic hexagonal crystalline symmetry in the core region is important for large modal overlap to efficiently generate THz radiation. The core and cladding of the fiber are made of Teflon with slightly different indices both at the pump and idler as well as THz frequencies. The core of the fiber consists of modified Teflon and Polyethylene inclusions of same radial dimension arranged in diatomic lattice with hexagonal symmetry. Input pump and idler fields are chosen to be at the frequencies of standard carbon dioxide and carbon monoxide lasers, respectively. The underlying photonic structure produces high efficiency of ∼15% with respect to pump power and moderately tunable THz radiation at about 9.2 THz within a very short 6.5 m propagation length. The pump power can be varied to tune the THz signal and the idler frequency in certain range. The optimized design also provides a low-loss guidance with propagation and bending losses of less than 1dB/km.