Measuring optical tunneling times using a Hong-Ou-Mandel interferometer.

Area of Science:

• Quantum optics
• Wave phenomena
• Interferometry

Background:

• Optical tunneling experiments measure light propagation through barriers.
• Hong-Ou-Mandel (HOM) interference is a key quantum optical phenomenon.
• Goos-Hänchen shift describes beam displacement at reflection, generalized here for frustrated total internal reflection.

Purpose of the Study:

• To predict the delay in optical tunneling experiments using HOM interference.
• To clarify assumptions for calculating tunneling delay with HOM interferometry.
• To investigate the nature of measured delays and rule out wavepacket reshaping explanations.

Main Methods:

• Utilizing Hong-Ou-Mandel interference to measure optical tunneling delay.
• Applying a generalized Goos-Hänchen shift for frustrated total internal reflection.
• Analyzing the HOM signal shape and comparing predicted delays with classical ones.

Main Results:

• The measured tunneling delay is identified as the group delay.
• Apparent superluminal propagation is observed for sufficiently thick air gaps.
• HOM signals with multiple minima can be obtained and are unaffected by the tunneling zone.
• Wavepacket reshaping is ruled out as an explanation for short tunneling delays.

Conclusions:

• The predicted tunneling delay is consistent with group delay.
• The phenomenon does not involve non-causal effects.
• HOM interference provides a robust method for studying optical tunneling dynamics.