Giant photothermal nonlinearity in a single silicon nanostructure

Area of Science:

• Photonics
• Nanotechnology
• Materials Science

Background:

• Silicon photonics are crucial for integrated optical devices and meta-optics.
• Achieving strong optical nonlinearity in silicon is challenging due to its intrinsically weak response.
• Current resonant structures for boosting nonlinearity often exceed 10 μm footprints.

Purpose of the Study:

• To investigate the nonlinear optical properties of nanoscale silicon structures.
• To explore the potential of silicon nano-resonators for enhanced optical nonlinearity.
• To demonstrate a pathway for nanoscale all-optical control and advanced imaging.

Main Methods:

• Fabrication of 100nm silicon nano-resonators.
• Utilizing Mie resonance to enhance light absorption and heating.
• Characterizing photothermal nonlinearity and thermal relaxation dynamics.

Main Results:

• Exhibited giant photothermal nonlinearity in 100nm silicon nano-resonators.
• Achieved 90% reversible and repeatable modulation from linear scattering.
• Demonstrated an equivalent nonlinear index five orders of magnitude larger than bulk silicon.
• Observed nanoscale thermal relaxation times in the nanosecond range.

Conclusions:

• 100nm silicon nano-resonators possess significant photothermal nonlinearity.
• This nonlinearity is enhanced by Mie resonance and efficient nanoscale heating.
• The demonstrated large and fast nonlinearity opens avenues for GHz all-optical control and super-resolution imaging.