Stably suppressing laser relative intensity noise on a 3 × 3 coupler interferometric system

Area of Science:

• Optical Engineering
• Signal Processing

Background:

• Interferometric systems are susceptible to working point drift and laser relative intensity noise (RIN).
• Existing demodulation schemes may not adequately address these noise sources, limiting measurement precision.

Purpose of the Study:

• To propose and validate a 3x3 coupler multiphase demodulation scheme.
• To eliminate the impact of working point drifting and RIN on interferometric systems.

Main Methods:

• Utilized a 3x3 coupler for multiphase signal generation.
• Applied an ellipse-fitting algorithm (EFA) to interference signals.
• Employed the ATAN algorithm to derive signals with trigonometric relationships.
• Averaged derived signals to eliminate RIN-induced phase noise.

Main Results:

• Demonstrated a significant reduction in noise floor: from 4.5 to 1 µrad/√Hz at 1 kHz and 2.7 to 0.8 µrad/√Hz at 3 kHz.
• Achieved an average noise floor reduction from 10 to 0.9 µrad/√Hz at high frequencies (approx. 21 dB).
• Reduced the variation range of the average noise floor from 5.4 to 0.17 µrad/√Hz within 100 s.

Conclusions:

• The proposed multiphase demodulation scheme effectively mitigates noise in 3x3 coupler interferometric systems.
• The EFA and ATAN algorithm combination provides robust phase demodulation with improved signal stability.
• This technique offers enhanced precision for optical sensing applications susceptible to environmental and laser noise.