ISO 11146-1:2021

Overview

ISO 11146-1:2021 specifies standardized test methods for laser beam widths (diameter), divergence angles and beam propagation ratios for stigmatic and simple astigmatic beams. The standard defines measurement principles based on the second‑order moments of the power (or energy) density distribution, coordinate systems (laboratory and principal axes), and required test arrangements and equipment. Measurements are made within the paraxial approximation; for unknown or general astigmatic beams, users are directed to ISO 11146‑2.

Key topics and technical requirements

• Scope and applicability: Applicable only to stigmatic and simple astigmatic laser beams; use ISO 11146‑2 for general astigmatic beams or unknown beam type.
• Measurement basis: Beam characterization using second‑order moments (first and second moments, beam centroids, principal axes).
• Beam parameters defined:
  • Beam widths/diameter based on second‑order moments (defined in the principal axes system).
  • Divergence angles and beam propagation ratio (M²) determination.
  • Beam ellipticity and principal‑axis azimuthal orientation.
• Test arrangement & equipment (Clause 6): Guidance on laboratory coordinate systems, detector systems, beam‑forming optics, optical attenuators, focusing systems and environmental control.
• Measurement procedures:
  • Beam width and diameter measurement (Clause 7) with prescribed evaluation methods.
  • Divergence angle measurement and evaluation (Clause 8).
  • Combined determination of waist locations, widths, divergence and beam propagation ratios (Clause 9).
• Reporting (Clause 10): Required test report contents to ensure traceability and repeatability.
• Practical notes: Methods assume paraxial beams and allow indirect techniques when direct measurement is difficult; ISO/TR 11146‑3 documents alternative methods (variable aperture, moving knife‑edge, moving slit). The 2021 edition harmonizes terms with ISO 11145 and refines principal‑axis definitions.

Applications and users

ISO 11146‑1 is intended for:

• Laser manufacturers validating beam quality and specification sheets.
• Test and calibration laboratories performing standardized beam measurements.
• System integrators and OEMs verifying beam performance in optical systems (material processing, medical lasers, sensing, communications).
• R&D and academic labs characterizing beams for experiments and publications.
• Regulatory and quality assurance teams ensuring consistent, comparable beam parameter reporting.

Using ISO 11146‑1 helps ensure repeatable, traceable measurements of laser beam widths, divergence angles, and M², improving interoperability and compliance across photonics applications.

Related standards

• ISO 11146‑2 - Test methods for general astigmatic beams
• ISO/TR 11146‑3 - Theoretical description and measurement alternatives (background subtraction, offset correction)
• ISO 11145 - Vocabulary and symbols (harmonized terminology)
• ISO 13694, EN 61040 - Related detector and power/energy density distribution methods

Keywords: ISO 11146-1:2021, laser beam widths, divergence angles, beam propagation ratio, stigmatic beams, simple astigmatic beams, test methods, second order moments, beam diameter measurement.