Using n- and p-Type Bi₂Te₃ Topological Insulator Nanoparticles To Enable Controlled Femtosecond Mode-Locking of Fiber Lasers

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.

Plasmonics in Topological Insulators: Spin–Charge Separation, the Influence of the Inversion Layer, and Phonon–Plasmon Coupling

“…[27][28][29][30] Also, plasmons in topological nano particles have been dealt with. 31,32 Here, we will focus on two aspects which we have discussed previously in Ref. 6,13 They are related to a thin slab of a topological insulator and involve the top and bottom surface that are separated by a strong dielectric defined by the width of the TI.…”

2D Saturable Absorbers for Fibre Lasers

“…All of these materials offer distinct, yet complementary properties [10,11,17,18] and, hence, new opportunities for optical applications in fibre-based systems. The possibility of combining layers of 2D materials to form van der Waals heterostructures also offers an exciting prospect for a wide range of new engineerable photonic devices [19], as does the potential to vary nanomaterial properties through their growth conditions, doping and electronic control [20,21].…”

Visible-wavelength pulsed lasers with low-dimensional saturable absorbers

“…Compared with the actively Q-switched and mode-locked lasers, which frequently depend on an acousto-optic modulator (AOM) [10] or an electro-optic modulator (EOM) [11] for pulsed operation, the passive ones that use low-dimensional nanomaterials as saturable absorbers (SAs) possess the merits of cost effectiveness, low optical loss, simplicity, and ease of integration into a laser system [12][13][14][15]. As deeply studied SAs, low-dimensional nanomaterials such as graphene [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31], topological insulators (TIs) [32][33][34][35][36][37][38][39][40], MXenes [41][42][43][44][45][46], transition-metal dichalcogenides (TMDs) [47][48][49][50][51][52][53][54][55]…”