In
recent years, the photoelectric properties and nonlinear optical properties
of layered metal chalcogenides (LMCs) have attracted extensive attentions.
Because of lower phonon thermal conductivity, larger energy storage
rate, and larger electron mobility, LMCs are widely studied in the
fields of thermoelectric energy conversion, battery electrode materials,
and semiconductor devices. As 2D LMCs, SnSe2 nanosheets
(Ns) are connected to each other by van der Waals force, which makes
it possible to use electrochemical methods to help peel off the thin
layer structure. Two-dimensional SnSe2 has obvious adjustable
band gap characteristics. Its thickness can be controlled to keep
it on the desired band gap. In this article, we prepared a thin layer
of SnSe2 by electrochemical methods and detected its nonlinear
optical characteristics. It shows that our prepared materials have
good optical absorption characteristics; it has a modulation depth
of 15% and a saturation intensity of 61 MW/cm2. To investigate
the nonlinear effects of SnSe2 in short and long cavities,
the Q-mode-locking phenomenon was first achieved in a fiber laser
with cavity length of 6 m. After increasing the cavity length to 56
m, the pump power is adjusted to achieve an adjustable repetition
frequency from MHz to GHz in turn in an Er-doped fiber laser through
utilizing an SnSe2 incorporating a tapered fiber as a saturable
absorber (SA). The nonlinear optical properties of thin layer SnSe2 are fully proven, which opens a new way for advanced photonics,
optical communication, laser measurement, and other fields.