1300-nm pulsed fiber lasers mode-locked by purified carbon nanotubes

For the first time, we demonstrate a novel passively mode-locked fiber laser operating at 1300 nm using purified single-walled carbon nanotubes (CNTs) as a saturable absorber. The saturable absorber incorporates diameter-controlled CNTs with peak absorption /spl sim/1300 nm, guaranteeing mode-locking over the same wavelength region. The ring laser uses praseodymium-doped fiber as a gain medium. The pulse repetition rate is 3.18 MHz, and the spectral half-width is 0.15 nm. Dual-wavelength mode-locking is also demonstrated with a channel spacing of 1.1 nm.

I. Introduction

Mode-Locked fiber lasers are a key source of subpicosecond optical pulses. Fig. 1. Absorption spectrum of SWNTs prepared by the “high-pressure CO conversion method” in CNI. The absorption peak covers 1300-nm spectral range, and has a depth of 5%. Among typical mode-locking schemes, passive mode-locking (especially using a saturable absorber) is attractive due to its structural simplicity and fast recovery time, resulting in fast loss modulation inside of the cavity and much shorter pulses compared with active mode-locking [1].