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Both experimental and theoretical works have demonstrated that two-dimensional materials exhibit strong thickness-dependent electronic and linear optical properties. However, the nonlinear optical (NLO) effect with respect to the thickness still needs to be further investigated, which is of great significance to design different photonic devices. Herein, we develop the physical vapor deposition technique to prepare a series of antimony selenide (Sb2Se 3) films. The relationship between the thickness of Sb2Se3 film and the NLO absorption was investigated by a Z -scan system under 35 fs, 800 nm laser excitation. The result shows the thicker Sb2Se3 film (∼ 50 nm) performs a larger third-order NLO susceptibility (Im χ (3)) approximately − 4. 5 9 × 1 0 − 8 esu, which can be interpreted by the stronger photon absorption, lower saturable intensity, and larger absorption cross-section of ground-state. More importantly, the Im χ (3) absolute value of thick Sb2Se3 film is also far larger than those of graphene, black phosphorus, transition metal dichalcogenide, MXenes, and heterostructure. This work demonstrates that Sb2Se3 film is an excellent saturable absorber and provides a promising application in nonlinear photonics. [ABSTRACT FROM AUTHOR]

Benefiting from the attractive high carrier mobility, large absorption coefficient, and ambient stability, group IV–VI compounds show excellent potential applications for optoelectronic devices. Herein, a germanium telluride (GeTe) film with a nanosphere structure has been controllably grown by facile physical vapor deposition and utilized into a photoelectrochemical (PEC)-type photodetector. The GeTe-based PEC-type photodetector possesses an excellent photoresponse and high responsivity in the visible region. Meanwhile, density functional theory calculations were employed to investigate the electronic characteristics of GeTe, supplying evidence of the broadband absorption. The improvement of photoelectric response can be attributed to the thicker films due to the larger light harvesting and higher carrier concentration, which is also verified by the visible–near-infrared absorption spectra and electrochemical impedance spectroscopy. The photocurrent density (Iph) and photoresponsivity (Rph) values of the GeTe-based photodetector can reach 22.8 μA/cm2 and 228.9 μA/W. Generally, our work provides an effective way to extend semiconductor materials in applications of PEC-type photodetectors. [ABSTRACT FROM AUTHOR]

We demonstrate an all fiber high-repetition-rate erbium-doped ultrashort laser based on the Ti3C2Tx-Mxene saturable absorber (SA), and the 56th harmonic mode-locking with a repetition rate of 622.2 MHz, a central wavelength of 1590.7 nm, and a pulse duration of 1.31 ps is achieved. Meanwhile, dual-wavelength mode-locking pulses are also realized, with the central wavelengths of 1575.6, 1587.5 nm. The results of the work indicate that Ti3C2Tx-Mxene is an outstanding SA for generating ultrashort pulse or modulating the light and the diversity Mxene family can bring new vigor and vitality into advanced photonic devices. [ABSTRACT FROM AUTHOR]

All-optical modulators based on a M X e n e - T i 3 C 2 T x have recently garnered much attention due to their broadband light-matter interactions and ultrafast carrier dynamics. To investigate the modulation characteristics of pump intensity and pump light modulation frequency, we establish an all-optical modulator with a sandwich structure based on M X e n e - T i 3 C 2 T x / P V A (polyvinyl alcohol) film. The result shows that this modulator can achieve a high modulation depth of 12.55 dB and a modulation frequency of 50 kHz corresponding to a response time at the microsecond scale. The successful preparation of the modulator is attributed to the saturable absorption characteristics of the M X e n e - T i 3 C 2 T x . This modulator has great potential in all-optical communications and ultrafast optical signal processing.