Active Etalon Stabilization for Precise Optical Spectrometer Performance

(Princeton Docket #20-3680)

Inventors: Gerard Wysocki, Chu Cheyenne Teng

Optical spectrometers are critical in environmental monitoring, industrial process control, and chemical analysis, where precision is paramount. However, parasitic interference fringes (etalons) caused by temperature fluctuations, mechanical vibrations, or pressure changes degrade long-term stability and accuracy. Traditional solutions, such as indirect temperature stabilization using thermistors or heuristic signal processing, fail to address the root cause of etalon drift, leading to persistent calibration demands and performance limitations.

This innovation directly measures etalon drift using spectral analysis of parasitic fringes. Key components include:

• Signal Processing: Fast Fourier Transform (FFT) and phase retrieval techniques extract fringe drift from the spectrometer’s transmission spectrum12.
• PID Feedback Control: A dynamic error signal adjusts actuators (e.g., thermoelectric coolers, piezoelectric elements) to stabilize the optical cavity length, targeting parameters like temperature, pressure, or mechanical position12.
• Dual Configurations:
  • Augmented Stabilization: Enhances conventional temperature control by reconciling thermistor readings with fringe-derived data12.
  • Direct Stabilization: Eliminates secondary sensors by using fringe drift as the primary feedback signal

Unlike conventional methods that indirectly target secondary parameters (e.g., temperature), this technology transforms parasitic fringes into a stabilization resource. Experimental results show a 20x improvement in temperature resolution and 10x longer stable integration times compared to thermistor-based systems

APPLICATIONS

ADVANTAGES

• Commercial Applications
• Gas Sensing: Methane detection in environmental monitoring, with demonstrated stability improvements in silicon photonic sensors.
• Industrial Process Control: Real-time spectral analysis in manufacturing (e.g., semiconductor fabrication).
• Free-Space Spectrometers: Stabilization of multi-pass cells used in high-precision laboratory instruments.
• Telecommunications: Enhanced performance of integrated photonic devices in optical networks.

• Precision: Direct etalon drift measurement reduces baseline noise, achieving Gaussian-limited stability for integration times up to 500 seconds.
• Adaptability: Applicable to integrated photonic sensors (e.g., silicon waveguides) and free-space optics (e.g., multi-pass cells).
• Cost Efficiency: Minimal hardware modifications enable economical upgrades to existing systems.
• Simplified Design: Eliminates reliance on indirect sensors, reducing system complexity.

Stage of Development

The inventors have experimentally verified the invention and demonstrated its effectiveness on a silicon photonic waveguide absorption methane sensor.

Contact
Renee Sanchez

New Ventures & Licensing Associate • (609) 258-6762 • renee.sanchez@Princeton.edu