Specialty Optical Fibers for THz Generation: A Review | Chapter 4 | Newest Updates in Physical Science Research Vol. 4

 This chapter describes cutting-edge terahertz (THz) radiation sources, with a focus on all-optical fiber-based THz generation. THz technology built on an optical fiber platform is expected to be the most appealing for everyday applications. Though optical fibers have previously been considered for low-loss THz radiation guidance, their nonlinear effects can also be used for THz generation. We will look at how a glass-based legacy step index fiber can be used to create a THz source. However, high absorption losses of silica glass in the THz regime, as well as a small overlap between optical and THz modes, limit THz generation efficiency to less than 0.01. With microstructured-core double-clad plastic fiber (MC-DCPF), both loss and modal overlap can be greatly reduced. This fiber's microstructure geometry enables fine tuning of the required phase matching condition, group-velocity dispersion, and nonlinear properties at the optical pump wavelength. Using such an MC-DCPF, we demonstrate that a THz wave with a frequency close to 3 THz can be generated using two commercially available high-power lasers. The high-power CO2 laser serves as the pump, while a much lower-power CO laser serves as the seed for the FWM process. According to numerical simulations, more than 30 W of THz power can be delivered within a bandwidth of 2.13 GHz. be generated at the end of a 65-meter-long fiber when 1 kW of CO2 laser power and 20 W of CO laser power are launched together. A conversion efficiency of 30% is possible in a loss-free configuration, but efficiency of more than 10% is possible even in the presence of material losses. According to recent findings, further optimization of such plastic microstructured fibers can provide conversion efficiencies of nearly 45 percent. As an alternative, we focused on the use of plastic fibers and discussed a design criterion that appears to be promising for realizing large output powers with relatively high efficiency.

Author (S) Details

Ajanta Barh
ETH Zürich, CH-8093, Switzerland.

R. K. Varshney
IIT Delhi, Delhi-110016, India.

G. P. Agrawal
University of Rochester, NY-14627, USA.

B. M. A. Rahman
City University London, EC1V 0HB, UK.

B. P. Pal
Mahindra University Ecole Centrale School of Engineering, Hyderabad-500043, India.

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