ISO 11145:2018

Overview

ISO 11145:2018 - "Optics and photonics - Lasers and laser-related equipment - Vocabulary and symbols" is the fifth-edition ISO standard that defines the basic terms, symbols and units used in laser technology. Its purpose is to unify laser terminology and enable clear, reproducible definitions and tests of beam parameters and laser-oriented product properties. The standard distinguishes between encircled-power definitions and second-moment (σ) definitions and documents conventions (for example, using the subscript u for percentage values and σ for second-moment–based quantities). Annex A explains differences between ISO 11145 and IEC 60825‑1 terminology.

Key topics and technical requirements

• Standardized definitions for core beam parameters:
  • Beam centroid (position), beam axis and beam positional stability
  • Beam diameter and beam radius (encircled-power and second-moment variants)
  • Beam width (slit-transmitted and second-moment), beam cross-sectional area, and ellipticity
  • Beam waist, divergence, Rayleigh length, beam parameter product (BPP)
• Laser characteristics and operation vocabulary:
  • Coherence, polarization, modes, optical resonator
  • Power and energy, pulse duration and repetition rate, spectral bandwidth, relative intensity noise (RIN) and efficiency
• Symbols and units section:
  • Uniform symbol list and recommended units to avoid ambiguity across measurements and reports
• Important conventions:
  • Use of encircled-power percentages (e.g., 90 %) versus second-moment definitions for different applications
  • Clear notation rules (u for percentages, σ for second-moment) to enable reproducible test results

Applications and users

ISO 11145:2018 is practical for anyone involved in laser specification, measurement and documentation:

• Laser and photonics manufacturers - for consistent product specifications and datasheets
• Optical test laboratories and calibrators - to ensure reproducible beam-parameter measurements
• System integrators and OEMs - to compare and select lasers by standardized metrics (BPP, beam waist, divergence)
• R&D engineers and researchers - for unambiguous reporting of experimental beam properties
• Standards developers and regulators - to align vocabulary across documents and jurisdictions

Related standards

• IEC 60825-1 (laser safety) - Annex A of ISO 11145 explains terminology differences; both standards serve different purposes and are complementary.
• ISO 11670 (beam angular/pointing stability) - referenced for related stability definitions.

Keywords: ISO 11145:2018, laser vocabulary, laser terminology, beam parameters, beam diameter, beam waist, divergence, beam centroid, beam propagation ratio, optics and photonics.