Foreword

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This document was prepared by Technical Committee 172, Optics and photonics, Subcommittee SC 9, Laser and electro-optical systems, in collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC 123, Lasers and photonics, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).

This fourth edition cancels and replaces the third edition (ISO 11551:2019), which has been technically revised.

The main changes are as follows:

harmonization of terms and environmental conditions to current laser measurement standards;
minor adjustments of formulae and figures;
modified text and additional figures in A.1 and A.3.

Any feedback or questions on this document should be directed to the user’s national standards body. A complete listing of these bodies can be found at www.iso.org/members.html.

Introduction

To characterize an optical component, it is important to know its absorptance. When radiation impinges upon a component, a part of that radiation is absorbed, increasing the temperature of the component. In this document only the part of the absorbed radiant power/energy, that is converted into heat, is measured. If enough radiant energy is absorbed, the optical properties of the component can change, and the component can even be destroyed. Absorptance is the ratio of the radiant flux absorbed to the radiant flux of the incident radiation.

In the procedures described in this document, the absorptance is determined calorimetrically as the ratio of radiant power or radiant energy absorbed by the component to the total radiant power or radiant energy, respectively, impinging upon the component. The assumption is made that the absorptance of the test sample is constant within the temperature fluctuations experienced by the component during the measurement.

1 Scope

This document specifies procedures and techniques for obtaining comparable values for the absorptance of optical laser components.

2 Normative references

3 Terms and definitions

4 Symbols and units of measure

5 Preparation of test sample and measuring arrangement

6 Characteristic features of the laser radiation

7 Test procedure

7.1 General

7.2 Calibration

7.3 Determining the absorptance

8 Evaluation

8.1 General

8.2 Elimination of drift

8.3 Exponential method

8.4 Pulse method

9 Test report

Bibliography