Large second-order susceptibility from a quantized indium tin oxide monolayer

Area of Science:

• Materials Science
• Optoelectronics
• Quantum Physics

Background:

• Indium tin oxide (ITO) thin films are vital for photonic circuits due to transparency and conductivity.
• Weak optical nonlinearity in ITO has hindered nonlinear signal processing.
• Developing novel materials with enhanced nonlinear optical properties is crucial.

Purpose of the Study:

• To investigate the nonlinear optical properties of atomically thin ITO films.
• To explore the potential of ITO-based quantum wells for nonlinear photonics.
• To identify the mechanisms behind enhanced nonlinear optical responses.

Main Methods:

• Fabrication of an air/indium tin oxide/SiO2 quantum well structure.
• Measurement of second-order nonlinear susceptibility (χ(2)).
• First-principles calculations and quantum electrostatic modeling.

Main Results:

• An ~1.5 nm ITO film in a quantum well structure exhibited a high second-order susceptibility (χ(2)) of ~1,800 pm/V.
• This χ(2) value is over 20 times greater than that of LiNbO3.
• Electronic interband transition resonance in an asymmetric potential was identified as the cause.

Conclusions:

• Atomically thin ITO quantum wells possess exceptionally large nonlinear optical responses.
• This design offers a promising pathway for developing efficient nonlinear photonic circuits.
• The findings could significantly advance integrated nonlinear optics and signal processing.