Non-instantaneous third-order optical response of gases in low-frequency fields

Area of Science:

• Quantum optics
• Atomic physics
• Nonlinear optics

Background:

• The third-order optical nonlinear response is typically assumed to be instantaneous for low-intensity, short optical pulses far from resonance.
• This assumption simplifies theoretical models but may not accurately reflect reality.

Purpose of the Study:

• To investigate the temporal response of the third-order optical nonlinearity in hydrogen.
• To determine if the polarization is instantaneously proportional to the electric field cubed.
• To analyze the intensity dependence of nonlinear optical effects and associated time delays.

Main Methods:

• Solving the three-dimensional time-dependent Schrödinger equation for a hydrogen atom.
• Analyzing fundamental-frequency and third-harmonic nonlinear susceptibilities.
• Simulating the response to short optical pulses far from resonance.

Main Results:

• The polarization response is not instantaneously proportional to the electric field cubed, even at low intensities.
• Delays in the Kerr response approach the femtosecond timescale at higher intensities.
• Delays in third harmonic generation remain significantly lower than Kerr response delays.

Conclusions:

• The instantaneous response assumption for third-order nonlinear optics is invalid for hydrogen.
• Time-resolved measurements are crucial for accurately characterizing nonlinear optical phenomena.
• Proposed experimental scheme to detect and measure these temporal effects.