Single- and double-walled carbon nanotube based saturable absorbers for passive mode-locking of an erbium-doped fiber laser

Abstract

The passive mode-locking of an erbium-doped fiber laser (EDFL) with a medium gain is demonstrated and compared by using three different types of carbon nanotubes (CNTs) doped in polyvinyl alcohol (PVA) films. Nano-scale clay is used to disperse the CNTs doped in the PVA polymer aqueous solution to serve as a fast saturable absorber to initiate passive mode-locking. The three types of CNT based saturable absorbers, namely single-walled (SW), double-walled (DW) and multi-walled (MW), are characterized by Raman scattering and optical absorption spectroscopy. The SW-CNTs with a diameter of 1.26 nm have two absorption peaks located around 1550 ± 70 and 860 ± 50 nm. In contrast, the DW-CNTs with a diameter of 1.33 nm reveal two absorption peaks located at 1580 ± 40 and 920 ± 50 nm. By using the SW-CNT based saturable absorber, the passively mode-locked EDFL exhibits a pulsewidth of 1.28 ps and a spectral linewidth of 1.99 nm. Due to the increased linear absorption of the DW-CNT based saturable absorber, the intra-cavity net gain of the EDFL is significantly attenuated to deliver an incompletely mode-locked pulsewidth of 6.8 ps and a spectral linewidth of 0.62 nm. No distinct pulse-train is produced by using the MW-CNT film as the saturable absorber, which is attributed to the significant insertion loss of the EDFL induced by the large linear absorption of the MW-CNT film.

Pulse-Width Saturation and Kelly-Sideband Shift in a Graphene-Nanosheet Mode-Locked Fiber Laser with Weak Negative Dispersion

“…Recently, carbon-based materials have shown their great potential for being promising saturable absorbers for passively-mode-locked fiber lasers, such as singlewalled carbon nanotubes (SWCNTs) [1][2][3][4][5][6][7], graphene [8][9][10], graphite [11,12], and charcoal nanoparticles [13]. At the initial stage, the SWCNT-incorporated saturable absorber has emerged with the advantages of an ultrafast relaxation time of <1 ps, a high optical damage threshold, a large optical nonlinearity, and polarization insensitivity [2][3][4].…”

Q-Switched Operation with Carbon-Based Saturable Absorbers in a Nd:YLF Laser

“…Carbon nanotubes have already been used to produce Q-switched [2] and mode-locked [3][4][5][6] laser pulses in bulk solid-state lasers. CNTs have been also used in fiber lasers using single-walled CNTs for the high-order harmonic mode locking [7] or single or double-walled CNTs for passive mode locking of erbium-doped fibers [8].…”

Multi-wavelength Q-switched erbium-doped fibre laser using saturable absorber based on carbon nanotube film

“…Up to date, many works have been reported on the integration of SWCNT/polyvinyl alcohol (PVA) SAs into fibre laser systems for ultra-short pulse generation (see, e.g., [8]). However, most of the works involving the SWCNT-based SAs have been directed at building mode-locked fibre lasers [9,10], while Q-switched fibre lasers have been addressed seldom enough [11]. Besides, a few works reported on the Q-switched lasers have been focused mainly on single-wavelength operation [2,11].…”