Probing ultra-fast dephasing via entangled photon pairs

Area of Science:

• Quantum Optics
• Ultrafast Spectroscopy
• Photonics

Background:

• Ultrafast dephasing is crucial for understanding light-matter interactions.
• Traditional methods for measuring dephasing often face limitations in sensitivity and dynamic range.
• Hong-Ou-Mandel (HOM) interference offers a potential avenue for enhanced probing capabilities.

Purpose of the Study:

• To demonstrate the utility of Hong-Ou-Mandel (HOM) interference with polarization-entangled photons for probing ultrafast dephasing.
• To show how optical properties, including complex susceptibility, can be inferred from HOM interference patterns.
• To establish a robust method for measuring dephasing times with high accuracy and visibility.

Main Methods:

• Utilizing polarization-entangled photons in a HOM interferometer.
• Analyzing changes in the position and shape of the HOM dip to extract information.
• Employing a continuous-wave (CW) laser source for the experiment.
• Developing a rigorous theoretical model to explain experimental observations.

Main Results:

• Successfully measured a dephasing time of 22 fs.
• Achieved high HOM dip visibility (92.3% to 96.7%) despite >97% optical loss.
• Demonstrated the ability to infer real and imaginary parts of complex susceptibility from HOM dip characteristics.
• Validated experimental findings with a comprehensive theoretical framework.

Conclusions:

• HOM interference is a powerful and sensitive technique for probing ultrafast dephasing.
• The method is robust against significant optical loss, maintaining high visibility.
• This approach provides valuable insights into the optical properties of materials and dephasing dynamics.