Low-loss single-mode guidance in large-core antiresonant hollow-core fibers.

We present an approach how to combine large-mode field diameters with effective single-mode guidance in a hollow-core antiresonant optical fiber. We demonstrate experimentally and in simulations that single-mode guidance is achieved in a simplified hollow-core fiber design with a core diameter of 30 μm by shifting the effective indices of the first cladding modes close to those of higher order core modes. Our fiber shows low loss propagation and effective single-mode operation from the near infrared to deep ultraviolet wavelengths down to 270 nm on a loss level of approximately 3  dB/m.