Entangled Two-Photon Absorption in Transmission-Based Experiments: Deleterious Effects from Linear Optical Losses

Area of Science:

• Quantum optics
• Nonlinear optics
• Spectroscopy

Background:

• Entangled two-photon absorption (ETPA) is an elusive quantum phenomenon studied in nonlinear materials.
• Transmission-based ETPA experiments are prone to artifacts from linear optical losses, casting doubt on reported results.
• Existing methods struggle to differentiate true ETPA signals from artifacts caused by optical losses.

Purpose of the Study:

• To investigate the impact of linear optical losses on ETPA detection.
• To introduce and validate a novel approach using Hong-Ou-Mandel (HOM) interferometry for ETPA studies.
• To demonstrate the ability of HOM interferograms to detect linear losses and their effect on ETPA signals.

Main Methods:

• Utilized rhodamine B solutions as a model nonlinear medium.
• Employed a Hong-Ou-Mandel interferometer as a sensing device to analyze ETPA.
• Introduced controlled linear losses using silica nanoparticles and varied solvent properties to study their effects.

Main Results:

• Demonstrated the equivalence between standard transmission-based ETPA experiments and the HOM interferogram approach (transmission vs. two-photon temporal delay).
• Quantified the detrimental effects of unrelated optical losses on ETPA signals in transmission experiments.
• Showcased the HOM interferogram's capability to identify the presence of linear optical losses.

Conclusions:

• Linear optical losses significantly compromise the accuracy of transmission-based ETPA experiments.
• Hong-Ou-Mandel interferometry offers a robust method for detecting linear losses in such experiments.
• Under the experimental conditions mimicking many published works, entangled two-photon absorption was not unequivocally detected, highlighting the need for improved detection methodologies.