Wavelength-Dependent Photothermal Imaging Probes Nanoscale Temperature Differences among Subdiffraction Coupled...

Area of Science:

• Nanophotonics and Plasmonics
• Optical Thermometry
• Nanoscale Heat Transfer

Background:

• Plasmonic nanostructures enable localized, controllable nanoscale heating.
• Optical thermometry is challenging for reading out temperature at the nanoscale.
• Understanding nanoscale thermal gradients is crucial for various applications.

Purpose of the Study:

• To demonstrate an all-optical thermometry technique for individual gold nanorod trimers.
• To investigate wavelength-dependent temperature distributions arising from plasmon modes.
• To correlate optical excitation of plasmon modes with thermal gradient control.

Main Methods:

• Utilizing photothermal microscopy to image temperature profiles.
• Analyzing the asymmetry of the photothermal image point spread function.
• Employing numerical simulations to interpret thermal gradients and plasmonic behavior.

Main Results:

• Individual gold nanorod trimers exhibit distinct, wavelength-dependent temperature distributions.
• Photothermal image asymmetry directly encodes local temperature profiles.
• Excitation of hybridized plasmon modes allows control over thermal gradients.
• Optically dark plasmon modes can be activated for thermal modification.

Conclusions:

• An all-optical thermometry method for creating and measuring nanoscale thermal gradients below the diffraction limit has been established.
• This technique offers precise control and readout of localized heating in plasmonic nanostructures.
• The findings provide a pathway for advanced applications in nanoscale thermal management and sensing.