Laser-self-mixing interferometry in the Gaussian beam approximation: experiments and theory.

Area of Science:

• Optics and Photonics
• Laser Physics
• Metrology

Background:

• Laser self-mixing interferometry is a technique for measuring displacement and vibration.
• Current models often use plane-wave approximations, limiting accuracy for Gaussian beams.
• Understanding Gaussian beam behavior is crucial for advanced laser sensing.

Purpose of the Study:

• To develop an improved model for laser self-mixing using Gaussian beam approximations.
• To enhance the accuracy and range of displacement measurements.
• To explore the capabilities of Gaussian beams for measuring target rotations and wobbling.

Main Methods:

• Analysis of the laser self-mixing process within the Gaussian beam approximation.
• Reformulation of the feedback coefficient (C) based on effective feedback power.
• Comparison of collimated and diverging Gaussian beams interacting with a plane mirror target.
• Development of a novel phase front reconstruction method using self-mixing scanning.

Main Results:

• A twenty-fold increase in the ratio of maximum to minimum measurable displacements predicted compared to plane-wave models.
• Diverging Gaussian beams demonstrate greater tolerance to target wobbling during displacement.
• Measurement of off-axis target rotations up to the beam's angular width is enabled.
• Successful demonstration of a novel phase front reconstruction technique.

Conclusions:

• The Gaussian beam approximation significantly improves laser self-mixing measurement capabilities.
• Diverging Gaussian beams offer enhanced robustness and expanded measurement possibilities.
• The developed model and methods pave the way for more precise laser-based sensing applications.