Nested antiresonant nodeless hollow core fiber.

We propose a novel hollow core fiber design based on nested and non-touching antiresonant tube elements arranged around a central core. We demonstrate through numerical simulations that such a design can achieve considerably lower loss than other state-of-the-art hollow fibers. By adding additional pairs of coherently reflecting surfaces without introducing nodes, the Hollow Core Nested Antiresonant Nodeless Fiber (HC-NANF) can achieve values of confinement loss similar or lower than that of its already low surface scattering loss, while maintaining multiple and octave-wide antiresonant windows of operation. As a result, the HC-NANF can in principle reach a total value of loss - including leakage, surface scattering and bend contributions - that is lower than that of conventional solid fibers. Besides, through resonant out-coupling of high order modes they can be made to behave as effectively single mode fibers.