Two-dimensional (2D) carbides of transition metals, so
called “MXenes”,
maintain excellent optical properties and unique layer stacking form
via hydrogen bonds in contrast to other low-dimensional materials.
These promising features have attracted increasingly research interest
in the field of ultrafast photonics. In this work, titanium carbide
(Ti3C2Tx) and tantalum
carbide (Ta4C3Tx), as two promising MXene materials for photonic applications, are
experimentally synthesized by the ultrasound-assisted liquid phase
exfoliation technique. The morphology of prepared few-layer Ti3C2Tx and Ta4C3Tx has been systematically
characterized by transmission electron microscopy and X-ray diffraction
analysis. Density functional theory is performed to obtain their electronic
band structures, demonstrating metallic properties and verifying their
optical absorption at 1 μm. Their tempting optical modulation
properties for multi-gigahertz pulsed laser emission are demonstrated
by using them as saturable absorbers in a waveguide laser cavity.
Particularly, high-performance Q-switched mode-locked
lasers with/without laser mirrors are realized based on the hybrid
waveguide laser configuration, delivering 1 μm laser pulses
with durations as short as 30 ps. The results presented in this work
show the great potential of metallic MXenes and waveguide structures
for applications in functional photonic devices.