Optical fibres embedded with as-grown carbon nanotubes for ultrahigh nonlinear optical responses.

Abstract

Photonic crystal fibre (PCF) embedded with functional materials has demonstrated diverse applications ranging from ultrafast lasers, optical communication to chemical sensors.[ 1] Many efforts have been made to fabricating carbon nanotube (CNT) based optical fibres by ex-situ transfer method, however, often suffer poor uniformity and coverage.[ 2] Here, wereport the direct growth of CNTs on the inner walls of PCFs by the chemical vapour deposition method. A two-step growth method wasdeveloped to control the narrow diametre distribution of CNTs to ensure desirable nanotube optical transitions. In the as-fabricated CNTs embedded fibre, third-harmonic generation has been enhanced by ∼15 times compared with flat CNT film on fused silica. Wefurther demonstrated a dual-wavelength all-fibre mode-locked ultrafast laser (∼1561nm and ∼1064nm) by integrating the 1.36±0.15nm-diametre CNTs into two kinds of photonic bandgap PCF (HC-1550 and HC-1060) as saturable absorbers, using their S11 (∼ 0.7eV) and S22 (∼ 1.2eV) interband transition respectively. The fibre laser showed stable output of ∼10mW, ∼800 fs pulse width and ∼71MHz repetition rate at 1561nm wavelength. Ourresults can enable the large-scale applications of CNTs in PCF-based optical devices. This article is protected by copyright. All rights reserved.