Pulse duration dependent optical nonlinearities of Bi₂Se₃ thin films

Area of Science:

• Condensed Matter Physics
• Materials Science
• Photonics

Background:

• Topological insulators (TIs) possess unique electronic properties.
• Bismuth selenide (Bi2Se3) is a prominent TI material known for its significant optical nonlinearities.

Purpose of the Study:

• To investigate the effect of laser pulse duration on the nonlinear optical responses of Bi2Se3 thin films.
• To understand the underlying mechanisms contributing to optical nonlinearities in Bi2Se3.

Main Methods:

• Utilized scanning electron microscopy (SEM) to characterize the crystalline structure of Bi2Se3 samples.
• Performed nonlinear optical measurements using 1030 nm laser excitation across a range of pulse durations (400 fs to 10 ps).

Main Results:

• Nonlinear absorption coefficients were quantified, ranging from -1.45 x10^-7 m/W to -4.86 x10^-7 m/W.
• Observed and discussed the influence of two distinct mechanisms on the observed optical nonlinearities.
• Established a direct comparison of results under identical experimental conditions.

Conclusions:

• Pulse duration is a critical parameter influencing the nonlinear optical behavior of Bi2Se3.
• The findings provide insights into the fundamental mechanisms governing optical nonlinearities in topological insulators.
• Results pave the way for optimizing Bi2Se3 for applications in nonlinear optics and photonics.