Sensitive detection of electric field-induced second harmonic signals

Area of Science:

• Nonlinear optics
• Quantum sensing
• Spectroscopy

Background:

• Electric field induced second harmonic generation (E-FISH) traditionally requires high optical fields and sensitive detectors.
• The technique's reliance on third-order hyperpolarizability and applied fields limits its application to high electric fields.

Purpose of the Study:

• To develop a more sensitive and efficient method for electric field measurements.
• To overcome the limitations of the conventional E-FISH technique.

Main Methods:

• Coherent homodyne amplification was applied to the E-FISH technique.
• An auxiliary beam, or local oscillator (LO), was superimposed with the E-FISH signal.
• The combined technique was named LOE-FISH (local oscillator enhanced E-FISH).

Main Results:

• A signal-to-noise ratio improvement of sevenfold was demonstrated.
• Measurement time was reduced by a factor of 49.
• The LOE-FISH technique shows increased sensitivity at lower electric field values.

Conclusions:

• LOE-FISH enables sensitive electric field measurements without intensified detectors.
• The technique allows for the use of lower energy pulsed lasers and MHz repetition rates, enabling real-time measurements.
• LOE-FISH presents a significant advancement with high potential for various applications.