Ternary transition metal chalcogenides (TTMDCs), a novel type of two-dimensional (2D) three-element materials, possess multiple physical and chemical properties and have promising potentials in basic physics and devices. Herein, the usage of WxNb(1−x)Se2 nanosheets as a rising ultrafast photonic device to generate high power mode-locked and Q-switched pulses in a fiber laser is demonstrated. The WxNb(1−x)Se2 nanosheets were successfully prepared by the liquid exfoliation method with thickness less than 3 nm. The nonlinear optical absorption of the WxNb(1−x)Se2-based device was investigated with the saturable intensity of 40.93 MW cm−2 and modulation depth of 5.43%. After integrating the WxNb(1−x)Se2-based device into an Er-doped fiber (EDF) laser cavity, mode-locking and Q-switching laser pulses were formed. In the mode-locked mechanism output, the pulse width is as narrow as 131 fs and the output power is 52.93 mW. In Q-switched operation, the shortest pulse duration is 1.47 μs with the largest pulse energy of 257 nJ. Compared to recent studies, our results showed some improvements. This study suggests that 2D TTMDC-based devices could be developed as efficient ultrafast photonics candidates and widely used in nonlinear optical applications.

WxNb(1-x)Se2 nanosheets for ultrafast photonics.

Two-dimensional (2D) transition metal chalcogenides (TMCs) become more attractive upon addition of a third element owing to their unique structure and remarkable physical and chemical properties, which endow these materials with considerable potential for applications in nanoscale devices. In this work, a RexNb(1-x)S2-based saturable absorber (SA) device for ultrafast photonics applications is studied. The device is assembled by placing RexNb(1-x)S2 nanosheets with a thickness of 1-3 nm onto a microfiber to increase their compatibility with an all-fiber laser cavity. The prepared RexNb(1-x)S2-based device exhibits a modulation depth of 24.3%, a saturation intensity of 10.1 MW/cm2, and a nonsaturable loss of 28.5%. Furthermore, the RexNb(1-x)S2-based device is used to generate ultrashort pulses in an erbium-doped fiber (EDF) laser cavity. At a pump power of 260 mW, the EDF laser operates in a conventional soliton mode-locked region. The pulse width is 285 fs, and the repetition frequency is 61.993 MHz. In particular, the bound-state soliton mode-locking operation is successfully obtained in a pump power range of 300-900 mW. The bound-state pulses are formed by doubling identical solitons with a temporal interval of 0.8 ps. The output power is as high as 47.9 mW, and the repetition frequency is 123.61 MHz. These results indicate that the proposed RexNb(1-x)S2-based SAs have comparable properties to currently used 2D SAs and provide a basis for their application in the field of ultrafast photonics.

Ultrafast Photonics of Ternary Re x Nb (1- x) S 2 in Fiber Lasers

A new kind of saturable absorber (SA) based on sol-gel technology was designed in this study. The integration of this SA is different from the traditional transmission coupling, which drops the TI/SiO2 sol-gel glass on the fiber end facet and forms a complete glass to cover the fiber core after drying naturally. According to the nonlinear optical character test, the modulation depth, saturable intensity and nonsaturable loss of this SA are 39.31%, 32.21 MW/cm2 and 13.41%, respectively. Besides, the SA based on sol-gel glass has a remarkable improvement in long-term stable mode-locking operation comparing with the SA based on organic film by aging-resistant testing and damage threshold of SA based on sol-gel glass increases by almost an order of magnitude. The fundamental mode-locking (FML) is observed at 1569 nm with pulse duration of 718 fs at the pump power of 90mW when this SA is integrated into the erbium-doped fiber (EDF) laser. As further increasing the pump power, the harmonic mode-locking (HML) appears. The highest harmonic order is to 119 with pulse duration of 4.48 ps at the pump power of 395mW. These results indicate that this TI/SiO2 SA prepared by the sol-gel method offers a new opportunity for the integration way of SA. 

119th harmonic mode-locking in the fiber laser based on a novel saturable absorber thin film obtained by the sol-gel method

The recent realization of topology as a mathematical concept in condensed matter systems has shattered Landau's widely accepted classification of phases by spontaneous symmetry breaking as he famously said, “a particular symmetry property exists or does not exist.” Topological materials (TMs) such as topological insulators and topological semimetals, are characterized by properties that depend on the topology of the band structure. Such dependence has drastic implications on the optical, electrical, and thermal properties of the material. Fundamental physics of TMs is currently under active research in condensed matter, materials science, and high energy physics. In this review, recent advances in exploiting the unique properties of TMs to realize functional optoelectronic devices are surveyed. Current and future applications that are, or may be, enabled by their unique properties are discussed. Although many theoretical ideas have been proposed over the past decade or so on using TMs in optoelectronic applications, the focus will be on experimentally realized devices.

https://rss.onlinelibrary.wiley.com/doi/am-pdf/10.1002/adfm.202110655

Topological Materials for Functional Optoelectronic Devices

A new kind of saturable absorber (SA) based on sol-gel technology was designed in this study. The integration of this SA is different from the traditional transmission coupling, which drops the TI/ SiO 2 sol-gel glass on the fiber end facet and forms a complete glass to cover the fiber core after drying naturally. According to the nonlinear optical character test, the modulation depth, saturable intensity and nonsaturable loss of this SA are 39.31%, 32.21 MW/ cm 2 and 13.41%, respectively. Besides, the SA based on sol-gel glass has a remarkable improvement in long-term stable mode-locking operation comparing with the SA based on organic film by aging-resistant testing and damage threshold of SA based on sol-gel glass increases by almost an order of magnitude. The fundamental mode-locking (FML) is observed at 1569 nm with pulse duration of 718 fs at the pump power of 90mW when this SA is integrated into the erbium-doped fiber (EDF) laser. As further increasing the pump power, the harmonic mode-locking (HML) appears. The highest harmonic order is to 119 with pulse duration of 4.48 ps at the pump power of 395mW. These results indicate that this TI/ SiO 2 SA prepared by the sol-gel method offers a new opportunity for the integration way of SA.

Study on the Energy Band Regulation of Bi2−xSbxTe3 and Its Application as Mode Locking Material in Low Gain Ultrafast Fiber Laser

Abstract High repetition frequency (HRF) ultrashort pulse fiber laser has been widely used in laser cold processing. The technical solutions such as short cavity length fiber laser have been proposed to achieve HRF ultrashort pulse output recently. However, the application of material-based saturable absorbers in this field has been astricted due to the low modulation depth, low damage resistance threshold, and high saturation fluence. Here, we designed a one-dimensional asymmetric photonic crystal with defect layer (1D-APCDL) as a novel saturable absorber, where the defect layer is Bi1.6Sb0.4Te3 with high modulation depth. The harmonic pulse with 3.82 GHz repetition frequency is achieved at the wavelength of 1562 nm, which is the highest repetition frequency of the topological insulator-based ring fiber laser so far to the best of our knowledge. The research provides a new saturable absorber solution, and provides a new idea for the application of material-based nonlinear optical chip in high-repetition frequency ultrashort pulse fiber lasers.

/pdf/gigahertz-femtosecond-laser-by-a-novel-asymmetric-one-1b1gysfc.pdf

Gigahertz femtosecond laser-by a novel asymmetric one-dimensional photonic crystal saturable absorber device with defect layer

Topological insulator (TI) as one of Two-dimensional (2D) materials has been widely used in the optoelectronic devices. However, further enhancements of output pulses in ultrafast fiber laser are limited by...

Study on the relationship between carrier mobility and nonlinear optical characteristics of Sb2Te3-Bi2Te3 lateral heterostructure materials and its applications in fiber lasers

The invention provides a one-dimensional photonic crystal and a preparation method thereof and an optical fiber laser. The preparation method of the one-dimensional photonic crystal comprises the following steps: S1, adding PVP into ethylene glycol to obtain a mixed solution; S2, adding sodium tellurite, bismuth chloride and sodium hydroxide into the mixed solution to obtain a precursor solution;S3, performing constant-temperature reaction on the precursor solution to obtain a reaction product; S4, centrifuging the reaction product to obtain a Bi2Te3 nanosheet precipitate; s5, drying the precipitate to obtain a Bi2Te3 nanosheet; S6, dissolving the Bi2Te3 nanosheet in water; S7, repeatedly plating Ta2O5 and SiO2 on the quartz substrate; S8, dropwise coating a Bi2Te3 aqueous solution; and S9, repeatedly coating SiO2 and Ta2O5. The reaction process for preparing the one-dimensional photonic crystal is mild, loss of reaction equipment is small, the prepared one-dimensional photonic crystal is good in stability, high in nonlinear performance and large in modulation depth, and the optical fiber laser prepared from the one-dimensional photonic crystal can achieve self-starting mode locking easily.

Chunyu Song

Papers

Study on the Energy Band Regulation of Bi2−xSbxTe3 and Its Application as Mode Locking Material in Low Gain Ultrafast Fiber Laser

119th harmonic mode-locking in the fiber laser based on a novel saturable absorber thin film obtained by the sol-gel method

Gigahertz femtosecond laser-by a novel asymmetric one-dimensional photonic crystal saturable absorber device with defect layer

Study on the relationship between carrier mobility and nonlinear optical characteristics of Sb2Te3-Bi2Te3 lateral heterostructure materials and its applications in fiber lasers

One-dimensional photonic crystal and preparation method thereof and optical fiber laser