An optimized scheme for detecting magneto-optic effects in ultrathin films with Sagnac interferometry

Area of Science:

• Condensed Matter Physics
• Materials Science
• Optics and Photonics

Background:

• Sagnac interferometry is crucial for measuring time-reversal symmetry breaking in magnetic materials.
• Conventional optical detection systems are often overwhelmed by ubiquitous birefringent effects.
• Optimizing optical power is essential for Sagnac interferometry sensitivity, especially when limited by amplifier noise.

Purpose of the Study:

• To demonstrate an experimental scheme for maximizing returning optical power in Sagnac interferometry.
• To enhance the detection of the magneto-optic effect in ultrathin magnetic films.
• To improve the signal-to-noise ratio for magneto-optic measurements.

Main Methods:

• Implementing a Sagnac interferometer with a highly reflective gold film.
• Utilizing the gold film to reflect the optical beam after interacting with the thin magnetic film.
• Applying the scheme to measure magnetization curves and Kerr rotation images.

Main Results:

• The gold film reflection increases returned optical power by a factor of 4-5.
• This leads to a 4-5 fold increase in signal-to-noise ratio for normal-incidence Sagnac interferometry.
• An expected 20-25 fold increase in signal-to-noise ratio for oblique-incidence Sagnac interferometry.

Conclusions:

• The demonstrated scheme effectively enhances optical power return in Sagnac interferometry.
• This technique significantly improves the sensitivity for detecting magneto-optic effects in ultrathin magnetic films.
• The method provides a robust approach for characterizing magnetic materials.