Impact of cladding elements on the loss performance of hollow-core anti-resonant fibers

TL;DR

This paper investigates how the geometry and size of nested elements in hollow-core anti-resonant fibers influence their loss performance, proposing optimized designs for ultra low-loss, wide-band single-mode operation.

Contribution

It reveals the dominant role of size over shape of nested elements, introduces a 'V-shape' mode suppression pattern, and demonstrates a novel anisotropic tube design achieving very low propagation loss.

Findings

5-tube nested HC-ARF has wider transmission window

Anisotropic tubes reduce propagation loss to 0.11 dB/km

Optimal nested element size improves single-mode, wide-band performance

Abstract

Understanding the impact of the cladding tube structure on the overall guiding performance is crucial for designing single-mode, wide-band, and ultra low-loss nested hollow-core anti-resonant fiber (HC-ARF). Here we thoroughly investigate on how the propagation loss is affected by the nested elements when their geometry is realistic (i.e., non-ideal). Interestingly, it was found that the size rather than the shape of the nested elements, have a dominant role in the final loss performance of the HC-ARFs. We identify a unique 'V-shape' pattern for suppression of higher-order modes loss by optimizing free design parameters of HC-ARF. We find that a 5-tube nested HC-ARF has wider transmission window and better single-mode operation than 6-tube HC-ARF. We show that the propagation loss can be significantly improved by using anisotropic nested anti-resonant tubes elongated in the radial direction. Our simulations indicate that with this novel fiber design, a propagation loss as low as 0.11 dB/km at 1.55 $\mu$m can be achieved. Our results provide design insights towards fully exploiting single-mode, wide-band, and ultra low-loss HC-ARF. In addition, the extraordinary optical properties of the proposed fiber can be beneficial for several applications such as future optical communication system, high energy light transport, extreme non-nonlinear optics and beyond.