Low-loss saturable absorbers based on tapered fibers embedded in carbon nanotube/polymer composites

Abstract

The emergence of low-dimensional materials has opened new opportunities in the fabrication of compact nonlinear photonic devices. Single-walled carbon nanotubes were among the first of those materials to attract the attention of the photonics community owing to their high third order susceptibility, broadband operation, and ultrafast response. Saturable absorption, in particular, has become a widespread application for nanotubes in the mode-locking of a fiber laser where they are used as nonlinear passive amplitude modulators to initiate pulsed operation. Numerous approaches have been proposed for the integration of nanotubes in fiber systems; these can be divided into those that rely on direct interaction (where the nanotubes are sandwiched between fiber connectors) and those that rely on lateral interaction with the evanescence field of the propagating wave. Tapered fibers, in particular, offer excellent flexibility to adjust the nonlinearity of nanotube-based devices but suffer from high losses (typically exceeding 50%) and poor saturable to non-saturable absorption ratios (typically above 1:5). In this paper, we propose a method to fabricate carbon nanotube saturable absorbers with controllable saturation power, low-losses (as low as 15%), and large saturable to non-saturable loss ratios approaching 1:1. This is achieved by optimizing the procedure of embedding tapered fibers in low-refractive index polymers. In addition, this study sheds light in the operation of these devices, highlighting a trade-off between losses and saturation power and providing guidelines for the design of saturable absorbers according to their application.

Gold Nanorods as Saturable Absorber for Harmonic Soliton Molecules Generation

“…Recently, researchers have reported that the two kinds of pulses, harmonic soliton molecules and rectangular noise-like pulses, can be coexisted in a fiber laser (Huang et al, 2016). In addition, different real saturable absorbers (SAs) can also be excellent composed for the generation of multiple pulses in the fiber laser cavity (Martinez et al, 2017; Lai et al, 2018). Other researchers reported that bound soliton and harmonic mode-locking soliton could be coexisted in an ultrafast fiber laser by MoS 2 SA for a photonic device (Liu et al, 2018).…”

Carbon nanotube mode-locked fiber lasers: recent progress and perspectives

“…Such interaction types originate from direct interaction between CNT and transmission light; however, high-power tolerance may be a limit. Other approach based on evanescent filed can be a candidate and SWNTs can be coated on a D-shaped fiber [171,172], microfiber [173,174], or injected into microslot [175,176], photonic crystal fiber [177] and hollow core fiber [178]. Recently, the development of SWNT SAs pays more attention on power handing, environmental stability and more outstanding SA characteristics including sol-gel method and glass doping [179,180].…”

Layered iron pyrite for ultrafast photonics application

“…Low-dimensional materials have attracted increasing attention in nonlinear optics due to their remarkable optoelectronic properties. For instance, one-dimensional carbon nanotubes (CNTs) and two-dimensional (2D) graphene were found to possess ultrafast carrier dynamics and high third-order nonlinear susceptibility [1][2][3][4][5][6][7][8][9]. Over the past decade, 2D materials have been widely reported in nonlinear optics, ultrafast photonics, and other fields due to their energy band structure and splendid crystals [10][11][12][13].…”