In our work, passively mode-locked and Q-switched Er-doped fiber lasers (EDFLs) based on titanium disulfide (TiS₂) as a saturable absorber (SA) were generated successfully. Stable mode-locked pulses centred at 1531.69 nm with the minimum pulse width of 2.36 ps were obtained. By reducing the length of the laser cavity and optimizing the cavity loss, Q-switched operation with a maximum pulse energy of 67.2 nJ and a minimum pulse duration of 2.34 µs was also obtained. Its repetition rate monotonically increased from 13.17 kHz to 48.45 kHz with about a 35 kHz tuning range. Our experiment results fully indicate that TiS₂ exhibits excellent nonlinear absorption performance and significant potential in acting as ultra-fast photonics devices.

A ferromagnetic insulator Cr₂Ge₂Te₆ as a saturable absorber in an Er-doped fiber laser (EDFL) was demonstrated. In this work, a CGT-PVA composite film was successfully fabricated using the liquid-phase exfoliation method and employed in an EDFL. The modulation depth and saturation intensity of the SA are 4.26% and 89.40 MW/cm², respectively. Stable pulses with a minimum pulse width of 978.5 fs when the repetition rate was 3.25 MHz were recorded experimentally. Furthermore, stable solitons still need to be obtained when the pulse energy in the cavity is as high as 11.6 nJ. The results fully suggest that CGT has outstanding nonlinear absorption properties, which may have broad potential applications in ultrafast photons.

We model optical bistability in all-dielectric guide-mode resonance grating (GMR) nanostructures working at quasi-bound states in the continuum (BICs). The complementary metal-oxide-semiconductor (CMOS) compatible material silicon nitride (SiN) is used for the design of nanostructures and simulations. The ultra-low threshold of input intensity in the feasible nanostructure for nanofabrication is obtained at the level of ~100 W/cm² driven by quasi-BICs. Additionally, the resonance wavelength in the GMR nanostructure can be widely tuned by incident angles with the slightly changed Q-factor that enables the optical bistable devices to work efficiently over a wide spectrum. The impact of the defects of grating that may be introduced in the fabrication process on the optical properties is discussed, and the tolerance of the defects to the optical performance of the device is confirmed. The results indicate that the GMR nanostructures of broadband and ultra-low threshold optical bistability driven by quasi-BICs are promising in the application of all-optical devices.

In this work, we introduced a Nd:YGG single mode planar waveguide fabricated by swift heavy ion irradiation. The initial Kr⁸⁺ ions beam energy was 2.1 GeV, after passing through the Al foil the beam energy came to 30 MeV. The implantation fluence was 2×10¹² ions/cm². A well region with the refractive index increment in near the surface was obtained after ion irradiation. This index increment was attributed to the ion-induced electronic damage. The characterization of the optical planar waveguide in Nd:YGG crystal was tested by prism coupling and end face coupling method. The micro-luminescence and Raman properties of our ion-irradiation Nd:YGG crystal were investigated. This work has reference value for integrated optical devices on Nd:YGG crystal.

In this study, titanium disulfide (TiS2) polyvinyl alcohol (PVA) film-type saturable absorber (SA) is synthesized with a modulation depth of 5.08% and a sa

We present a portable single-shot lens-free tomographic microscope, based on spatial multiplexing in-line digital holography, for three-dimensional (3D) imaging of dynamic specimens. The simplified system is realized by only a laser diodes array, a rectangular aperture, and a CMOS image sensor with a global shutter, which enables the recording of all the complex fields of a dynamic specimen from different illumination angles without any scanning mechanism by a multiplexing hologram, in a single camera exposure. Using our proposed data processing method, high-quality 3D tomograms, with a lateral resolution of 3.36μm and an axial resolution of 6.39μm within an imaging field-of-view of 5.06 mm², can be eventually reconstructed from a multiplexing hologram. Experimental results of free-swimming paramecium in water demonstrates the systems potential in 3D imaging living or rapidly moving specimens in resource-limited environments.