Abstract
A hollow-core photonic crystal fibre (HC-PCF) based on small-pitch kagome lattice cladding is designed and fabricated. The pitch of the fibre is only 2.45μm and it corresponds to a region of low normalized frequency which has never been investigated before. Both experiments and calculations show that this kagome HC-PCF has a broad optical transmission band from 400 nm to 900 nm, covering the whole visible and near infrared region of the spectrum. Additionally, the loss curve of the fibre is flat in the visible region and the minimum of the loss achieves 0.16dB/m, which is lower than the loss of the kagome HC-PCFs reported before. Furthermore, this fibre can well confine the modes in the air core. No surface modes can be detected in the surrounding silica of the hollow core.