Abstract
We report a large third-order nonlinear optical response of palladium
diselenide (PdSe2) films – a two-dimensional (2D) noble
metal dichalcogenide material. Both open-aperture (OA) and
closed-aperture (CA) Z-scan measurements are performed with a
femtosecond pulsed laser at 800 nm to investigate the nonlinear
absorption and nonlinear refraction, respectively. In the OA experiment,
we observe optical limiting behaviour originating from large two photo
absorption (TPA) in the PdSe2 film of β = 3.26 ×
10-8 m/W. In the CA experiment, we measure a
peak-valley response corresponding to a large and negative Kerr
nonlinearity of n2 =
-1.33×10-15 m2/W – two orders of
magnitude larger than bulk silicon. We also characterize the variation
of n2 as a function of laser intensity, observing
that n2 decreases in magnitude with incident
laser intensity, becoming saturated at n2 =
-9.96×10-16 m2/W at high
intensities. These results verify the large third-order nonlinear
optical response of 2D PdSe2 as well as its strong
potential for high performance nonlinear photonic devices.