Direction-Dependent Plasmonic Chiroptical Response With High Asymmetry and Dynamic Tunability

Area of Science:

• Plasmonics
• Chiroptical materials
• Nanomaterials

Background:

• Direction-dependent chiroptical response offers enhanced control beyond conventional circular dichroism (CD).
• Existing direction-asymmetric chiroptical materials often use isotropic films with weak signals.

Purpose of the Study:

• To develop a plasmonic-based chiroptical film with a strong, direction-dependent CD signal.
• To achieve programmable and tunable chiroptical modulation for advanced applications.

Main Methods:

• Linear assembly of gold nanospheres (AuNSs) on an elastomeric polymer substrate.
• Inducing geometrical chirality through wrinkle formation via mechanical stretching.
• Investigating the interplay between AuNSs linear dichroism and polymer strain-induced linear birefringence.

Main Results:

• Demonstrated reversal of CD handedness by changing light propagation direction (forward/backward).
• Achieved significantly enhanced CD intensity (from -0.8 to 10.8 deg), exceeding previous systems by 2-3 orders of magnitude.
• Showcased programmable control over CD signal (on/off, ellipticity magnitude, handedness) by varying mechanical stretching and orientation.

Conclusions:

• The developed plasmonic film provides a strong, direction-dependent CD response with multiple degrees of freedom for dynamical modulation.
• This material presents a promising platform for circularly-polarized light-based information encryption.