In recent years, MXene has become a hotspot because of its good conductivity, strong broadband absorption, and tunable band gap. In this contribution, 0D MXene Ti 3 C 2 T x quantum dots are synthesized by a liquid exfoliation method and a wideband nonlinear optical response from 800 to 1550 nm is studied, which have a larger nonlinear absorption coefficient of-(11.24 ± 0.14) × 10-2 cm GW-1. The carrier dynamic processes of 0D MXene are explored with ultrahigh time resolution nondegenerate transient absorption (TA) spectroscopy, which indicates that the TA signal reaches its maximum in 1.28 ps. Furthermore, 0D MXene is used to generate ultrashort pulses in erbium or ytterbium-doped fiber laser cavity. High signal-to-noise (72 dB) femtosecond lasers with pulse durations as short as 170 fs with spectrum bandwidth of 14.8 nm are obtained. Finally, an ultranarrow fiber laser based on 0D MXene is also investigated and has a full width at half maximum of only 5 kHz, and the power fluctuation is less than 0.75% of the average power. The experimental works prove that 0D MXene is an excellent SA and has a promising application in ultrafast and ultranarrow photonics.

Transition metal carbides and nitrides (MXene) quantum dots (QDs) are potentially important for versatile applications, including ultra‐narrow photonics. Here, a simple method for controlling the sizes and solution concentrations of Ti2C‐MXene‐QDs are shown, and then their optical properties are systematically investigated and compared. The nonlinear optical characteristics of QDs can be adjusted through the QD size and solution concentration. QDs with smaller sizes of 1–3 nm have stronger absorptivity, larger modulation depth and lower nonsaturable loss, and QDs with higher concentrations have stronger absorptivity and larger modulation depth but higher nonsaturable loss. These QDs are further applied to construct loop‐cavity ultranarrow lasers whose narrowest laser linewidth is 624.5 Hz, highest signal‐to‐noise ratio (SNR) is 77.63 dB and lowest power fluctuation is 0.4%. A comparison of these indicators indicates that smaller and more homogeneous MXene QD solutions with proper concentrations favor ultra‐narrow photonics. The laser power is also amplified to ≈60 mW by an erbium‐doped fiber amplifier (EDFA).

MXene, as a novel two-dimensional (2D) material saturable absorber (SA), has excellent nonlinear optical characteristics and strong photo-materials interactions.

Abstract2D semi‐metallic hafnium ditelluride material is used in several applications such as solar steam generation, gas sensing, and catalysis owing to its strong near‐infrared absorbance, high sensitivity, and distinctive electronic structure. The zero‐bandgap characteristics, along with the thermal and dynamic stability of 2D‐HfTe2, make it a desirable choice for developing long‐wavelength‐range photonics devices. Herein, the HfTe2‐nanosheets are prepared using the liquid‐phase exfoliation method, and their superior nonlinear optical properties are demonstrated by the obtained modulation depth of 11.9% (800 nm) and 6.35% (1560 nm), respectively. In addition, the observed transition from saturable to reverse saturable absorption indicates adaptability of the prepared material in nonlinear optics. By utilizing a side polished fiber‐based HfTe2‐saturable absorber (SA) inside an Er‐doped fiber laser cavity, a mode‐locked laser with 724 fs pulse width and 56.63 dB signal‐to‐noise ratio (SNR) is realized for the first time. The generated laser with this SA has the second lowest mode‐locking pump threshold (18.35 mW), among the other 2D material based‐SAs, thus paving the way for future laser development with improved efficiency and reduced thermal impact. Finally, employing this HfTe2‐SA, a highly stable single‐frequency fiber laser (SNR ≈ 74.56 dB; linewidth ≈ 1.268 kHz) is generated for the first time, indicating its promising ultranarrow photonic application.