Real-time complex amplitude reconstruction method for beam quality M² factor measurement.

Area of Science:

• Optics and Photonics
• Laser Physics
• Metrology

Background:

• Accurate measurement of laser beam quality is crucial for applications.
• Existing methods for determining the beam propagation ratio (M²) can be time-consuming or complex.
• The transport of intensity equation (TIE) offers a potential avenue for rapid beam characterization.

Purpose of the Study:

• To develop and validate a real-time complex amplitude reconstruction method for determining the M² factor of laser beams.
• To establish a fast and accurate technique for laser beam quality assessment.
• To enable the investigation of laser beams in challenging experimental conditions.

Main Methods:

• Utilized a synchronous acquisition system with two CCD cameras to capture intensity images at different axial positions.
• Employed the transport of intensity equation (TIE) algorithm for rapid complex amplitude reconstruction.
• Applied angular spectrum (AS) theory to propagate the beam intensity.
• Calculated the M² factor using second-order moments and hyperbola fitting, adhering to ISO standards.

Main Results:

• Successfully reconstructed the complex amplitude of laser beams in real-time.
• Demonstrated accurate M² factor calculation for both He-Ne and high-power fiber laser sources.
• Validated the method through numerical analysis and experimental verification.
• The developed technique proved to be simple, fast, and versatile.

Conclusions:

• The presented TIE-based method provides a rapid and accurate approach for determining laser beam quality (M²).
• This technique overcomes limitations of conventional methods, allowing for measurements in previously inaccessible scenarios.
• The simplicity and speed of the experimental setup make it suitable for diverse laser characterization applications.