Model-Based, Closed-Loop Control of PZT Creep for Cavity Ring-Down Spectroscopy

Area of Science:

• Spectroscopy
• Optical Engineering
• Instrument Science

Background:

• Cavity ring-down spectrometers commonly use PZT stacks for spectral modulation.
• PZT hysteresis complicates cavity-length stabilization and precise data acquisition.
• Existing methods to mitigate hysteresis, like frequency-stabilized cavity ring-down spectroscopy, are complex for commercial use.

Purpose of the Study:

• To present a novel, simplified method for cavity length control in spectrometers.
• To address the challenge of PZT hysteresis in achieving stable cavity-length measurements.
• To enable more accessible and precise spectroscopic data acquisition.

Main Methods:

• Development of a single-laser, model-based, closed-loop control system.
• Implementation of a routine for cavity length stabilization.
• Utilizing the cavity's free spectral range for precise wavelength axis calibration.

Main Results:

• Demonstration of a closed-loop system effectively controlling cavity length.
• Mitigation of PZT hysteresis issues without significant added complexity.
• Achieved high linearity and precision in the measured spectrum's wavelength axis.

Conclusions:

• The proposed method offers a practical solution for cavity length control in spectrometers.
• This approach simplifies instrument design while maintaining measurement accuracy.
• The technique has potential for broader commercial application in spectroscopy.