Using n- and p-Type Bi<inf>2</inf>Te<inf>3</inf> topological insulator nanoparticles to enable controlled femtosecond mode-locking of fiber lasers
Journal
ACS Photonics
Journal Volume
2
Journal Issue
4
Pages
481-490
Date Issued
2015
Author(s)
Lin, Y.-H.
Lin, S.-F.
Chi, Y.-C.
Wu, C.-L.
Cheng, C.-H.
Tseng, W.-H.
He, J.-H.
Wu, C.-I.
Lee, C.-K.
Abstract
Mechanically triturated n- and p-type Bi2Te3 nanoparticles, the nanoscale topological insulators (TIs), are employed as nonlinear saturable absorbers to passively mode-lock the erbium-doped fiber lasers (EDFLs) for sub-400 fs pulse generations. A novel method is proposed to enable the control on the self-amplitude modulation (SAM) of TI by adjusting its dopant type. The dopant type of TI only shifts the Fermi level without changing its energy bandgap, that the n- and p-type Bi2Te3 nanoparticles have shown the broadband saturable absorption at 800 and 1570 nm. In addition, both the complicated pulse shortening procedure and the competition between hybrid mode-locking mechanisms in the Bi2Te3 nanoparticle mode-locked EDFL system have been elucidated. The p-type Bi2Te3 with its lower effective Fermi level results in more capacity for excited carriers than the n-type Bi2Te3, which shortens the pulse width by enlarging the SAM depth. However, the strong self-phase modulation occurs with reduced linear loss and highly nonsaturated absorption, which dominates the pulse shortening mechanism in the passively mode-locked EDFL to deliver comparable pulse widths of 400 and 385 fs with n- and p-type Bi2Te3 nanoparticles, respectively. The first- and second-order Kelly sidebands under soliton mode-locking regime are also observed at offset frequencies of 1.31 and 1.94 THz, respectively.
SDGs
Type
journal article