Ultrafast Fiber Lasers with Low-Dimensional Saturable Absorbers: Status and Prospects

Abstract

Wide-spectral saturable absorption (SA) in low-dimensional (LD) nanomaterials such as zero-, one-, and two-dimensional materials has been proven experimentally with outstanding results, including low saturation intensity, deep modulation depth, and fast carrier recovery time. LD nanomaterials can therefore be used as SAs for mode-locking or Q-switching to generate ultrafast fiber laser pulses with a high repetition rate and short duration in the visible, near-infrared, and mid-infrared wavelength regions. Here, we review the recent development of emerging LD nanomaterials as SAs for ultrafast mode-locked fiber laser applications in different dispersion regimes such as anomalous and normal dispersion regimes of the laser cavity operating in the near-infrared region, especially at ~1550 nm. The preparation methods, nonlinear optical properties of LD SAs, and various integration schemes for incorporating LD SAs into fiber laser systems are introduced. In addition to these, externally (electrically or optically) controlled pulsed fiber laser behavior and other characteristics of various LD SAs are summarized. Finally, the perspectives and challenges facing LD SA-based mode-locked ultrafast fiber lasers are highlighted.

Incoherent laser

“…Natural saturable absorbers are attractive because of their accessibility and available variety [37][38][39][40][41]. Their fundamental problem arises from degradation of their properties over time and, therefore, limited useful life time.…”

Bimetallic solid solution MAX phase Ti2NbAlC2 as saturable absorber for passively Q-switched Er3+-doped fiber laser

“…In the past decade, diverse nonlinear optical materials have been researched as SAs, including graphene [5,6], topological insulators (TIs) [7,8], transition metal dichalcogenides (TMDs) [9,10], black phosphorus (BP) [11], carbon nanotubes (CNTs) [12,13], chromium oxide [14], semiconductor saturable absorber mirrors (SESAMs) [15], etc. Nevertheless, these SA materials have their draw backs, for instance, the low modulation depth of single-layer graphene limits its applications in optical modulation [16], the low damage threshold of nanomaterials-based SAs limits the generation of high energy pulse [17], the complex fabrication process and long recovery time of TIs hinder the ultrafast laser to generate [18], the properties of TMDs is related to the number of layers [19], the easy-oxidative feature of BP in the air is adverse for the longterm stability [20], and the complex design and costly price of SESAMs are still a problem [21]. Therefore, the research of saturable absorbers needs to be expanded and consummated continuously.…”

Preparation of High Damage Threshold Device Based on Bi2Se3 Film and Its Application in Fiber Lasers

“…In recent years, researchers have used graphene, , black phosphorus, transition metal oxide, , topological insulator (TI), , and other thin film materials as SA, − then they observed the output phenomenon of femtosecond pulse laser in the near-infrared and mid-infrared bands. Although 2D materials have their own unique advantages, there are inevitably short plates, which means that it is difficult for us to define a design where all parameters tend to be perfect. More attention needs to be paid to the balance and selection of various parameters.…”