Excess noise reduction by optical technique in amplitude-sensitive heterodyne interferometer for small differential...

Area of Science:

• * Optics and Photonics
• * Interferometry
• * Precision Measurement

Background:

• * Heterodyne interferometers are crucial for detecting small phase shifts.
• * Traditional methods often struggle with excess noise and require phase locking.
• * Amplitude-sensitive techniques offer potential for improved noise reduction.

Purpose of the Study:

• * To report an amplitude-sensitive technique for differential phase detection using a heterodyne interferometer.
• * To reduce excess noise via optical subtraction, enhancing measurement sensitivity.
• * To demonstrate real-time differential phase determination without phase lock-in.

Main Methods:

• * Employing an amplitude-sensitive technique with a heterodyne interferometer.
• * Utilizing optical subtraction to mitigate excess noise.
• * Converting differential phase to signal amplitudes for simultaneous quadrature detection.

Main Results:

• * Demonstrated differential phase detection resolutions close to 10⁻⁶ rad/√Hz (10⁻¹³ m/√Hz) over 100 kHz bandwidth.
• * Achieved resolutions of 10⁻⁸ rad/√Hz (10⁻¹⁵ m/√Hz) over 125 MHz bandwidth with 2.5 mW incident power.
• * Showcased advantages of optical differential and additive operations for real-time measurements.

Conclusions:

• * The developed technique effectively reduces excess noise through optical subtraction.
• * High-resolution differential phase detection is achievable in real-time without phase lock-in.
• * The method offers significant improvements in sensitivity and bandwidth for precision optical measurements.