oSIST prEN ISO 11145:2025

SLOVENSKI STANDARD
01-junij-2025
Optika in fotonska tehnologija - Laserji in z laserji povezana oprema - Slovar in
simboli (ISO/DIS 11145:2025)
Optics and photonics - Lasers and laser-related equipment - Vocabulary and symbols
(ISO/DIS 11145:2025)
Optik und Photonik - Laser und Laseranlagen - Begriffe und Formelzeichen (ISO/DIS
11145:2025)
Optique et photonique - Lasers et équipements associés aux lasers - Vocabulaire et
symboles (ISO/DIS 11145:2025)
Ta slovenski standard je istoveten z: prEN ISO 11145
ICS:
01.040.31 Elektronika (Slovarji) Electronics (Vocabularies)
31.260 Optoelektronika, laserska Optoelectronics. Laser
oprema equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 11145
ISO/TC 172/SC 9
Optics and photonics — Lasers
Secretariat: DIN
and laser-related equipment —
Voting begins on:
Vocabulary and symbols
2025-04-03
Optique et photonique — Lasers et équipements associés aux
Voting terminates on:
lasers — Vocabulaire et symboles
2025-06-26
ICS: 31.260; 01.040.31
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
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USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
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POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS.
RECIPIENTS OF THIS DRAFT ARE INVITED
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NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Reference number
ISO/DIS 11145:2025(en)
DRAFT
ISO/DIS 11145:2025(en)
International
Standard
ISO/DIS 11145
ISO/TC 172/SC 9
Optics and photonics — Lasers
Secretariat: DIN
and laser-related equipment —
Voting begins on:
Vocabulary and symbols
Optique et photonique — Lasers et équipements associés aux
Voting terminates on:
lasers — Vocabulaire et symboles
ICS: 31.260; 01.040.31
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2025
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
BE CONSIDERED IN THE LIGHT OF THEIR
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NATIONAL REGULATIONS.
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NOTIFICATION OF ANY RELEVANT PATENT
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Website: www.iso.org
Published in Switzerland Reference number
ISO/DIS 11145:2025(en)
ii
ISO/DIS 11145:2025(en)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 Beam position .2
3.2 Beam axis .2
3.3 Beam diameter .3
3.4 Beam radius .3
3.5 Beam width . . .4
3.6 Beam cross-sectional area .4
3.7 Beam waist . .5
3.8 Divergence .7
3.9 Rayleigh length .7
3.10 Beam parameter product .8
3.11 Coherence .8
3.12 Polarization .9
3.13 Power and Energy .10
3.14 Pulse duration and repetition rate .11
3.15 Optical resonator .11
3.16 Mode. 12
3.17 Spectral bandwidth . 12
3.18 Relative intensity noise . . . 12
3.19 Laser . 12
3.20 Efficiency . 13
4 Symbols and units of measurement . 14
Annex A (informative) Explanation of the difference in terminology between IEC 60825-1 and
ISO 11145 . 16
Annex B (informative) List of symbols . 17
Bibliography .18
Alphabetical index . 19

iii
ISO/DIS 11145:2025(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent
rights identified during the development of the document will be in the Introduction and/or on the ISO list of
patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 172, Optics and photonics, Subcommittee SC 9,
Laser and electro-optical systems.
This sixth edition cancels and replaces the fifths edition ISO 11145:2018, which has been technically revised.
The main changes compared to the previous edition are as follows:
— the term “power density” was replaced by “irradiance”, “energy density” was replaced by “fluence” and
“radiant” was added to “power (energy)”.
— To the Terms 3.3.1, 3.4.1, 3.6.1, 3.7.4, 3.7.6, 3.8.1 “encircled-power” was added.
— To the Terms 3.5.1 and 3.7.8 “slit-transmitted-power” was added.
— Term and definition 3.5.3 “principal axes” was newly added.
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.

iv
DRAFT International Standard ISO/DIS 11145:2025(en)
Optics and photonics — Lasers and laser-related equipment
— Vocabulary and symbols
1 Scope
This document defines basic terms, symbols, and units of measurement for the field of laser technology in
order to unify the terminology and to arrive at clear definitions and reproducible tests of beam parameters
and laser-oriented product properties.
NOTE The laser hierarchical vocabulary laid down in this document differs from that given in IEC 60825–1.
ISO and IEC have discussed this difference and agree that it reflects the different purposes for which the two standards
serve. For more details, see informative Annex A.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
NOTE 1 The spatial distribution of the irradiance (fluence) in a cross section of a laser beam does not always have
circular symmetry. In this document, all terms related to these spatial distributions are split into those for beam cross
sections with circular distributions and those for beam cross sections with non-circular distributions. A circular
beam is characterized by its radius, w, or diameter, d. For a non-circular beam, the beam widths, d and d , for two
x y
orthogonal directions are given.
NOTE 2 The spatial distributions of laser beams do not have sharp edges. Therefore, the radiant power (energy)
values to which the spatial terms refer are defined. Depending on the application, different cut-off values can be
chosen (for example 1/e, 1/e , 1/10 of the peak value).
NOTE 3 This document uses the subscript u to denote a percentage. For example, the percentage of the total beam
power (energy) included in the value of a given parameter. When stating quantities marked by an index “u”, “u” is
replaced by the specific number, e.g. A for u = 90 %.
NOTE 4 The beam width d (see 3.5.1) and the beam diameter d (see 3.3.1) can differ for the same value of u (d ≠ d ).
ux u ux u
NOTE 5 In contrast to quantities defined by setting a cut-off value [“encircled radiant power (energy)”], the beam
widths and derived beam properties can also be defined based on the second-order moments of the irradiance
(fluence) distribution function (see 3.5.2). Only beam propagation ratios (see 3.10.2) that are calculated from beam
widths and divergence angles derived from the second-order moments of the irradiance (fluence) distribution function
allow calculation of beam propagation. In this document, quantities based on the second-order moment are marked by
a subscript “σ”.
NOTE 6 A list of symbols is given in Annex B.

ISO/DIS 11145:2025(en)
3.1 Beam position
3.1.1
beam centroid
xz , yz
() ()
coordinates of the first-order moments of a radiant power (energy) distribution of a beam at location z
xE⋅ ()xy,,zx⋅ddy
∫∫
xz() =
Ex(),,yz ⋅ddxy
∫∫
yE⋅ ()xy,,zx⋅ddy
∫∫
yz =
()
Ex(),,yz ⋅ddxy
∫∫
where the integration shall be performed over an area such that at least 99 % of the beam power (energy) is
captured
Note 1 to entry: The irradiance E is replaced by the fluence H for pulsed lasers.
Note 2 to entry: The terms beam centroid, centre of gravity and beam position are equivalent, formerly the term beam
position was used.
Note 3 to entry: These quantities are defined in the beam axis system x,y,z, in which z is the direction of propagation
of the beam.
3.1.2
beam positional stability
Δx(z'), Δy (z')
four times the standard deviation of the measured beam positional movement at plane z′
N 2
 ′′ 
xz() −xz()
∑  i 
i=1
′
Δxz()=4
N−1
N 2
yz′′− yz 
() ()
∑
 i 
i=1
′
Δyz()=4
N−1
′ ′ ′ ′
where xz() and yz() are the beam centroids in the z′ plane, xz() and yz() are the arithmetic mean
beam centroids in the z′ plane, and N is the number of measurements
Note 1 to entry: The term "beam positional stability" is sometimes referred to as “spatial fluctuation widths”, as in
ISO 11670.
3.2 Beam axis
3.2.1
beam axis
straight line connecting the centroids defined by the first-order spatial moments of the cross-sectional
irradiance (fluence) distribution function at successive locations in the direction of propagation (z) of the
beam in a homogeneous medium
3.2.2
misalignment angle
Δϑ
deviation angle of the beam axis from the mechanical axis defined by the manufacturer

ISO/DIS 11145:2025(en)
3.3 Beam diameter
3.3.1
encircled-power beam diameter
d (z)
u
diameter of a circular aperture in a plane perpendicular to the beam
axis that contains u % of the total beam power (energy)
Note 1 to entry: For clarity, the term “beam diameter” is always used in combination with the symbol and its
appropriate subscript: d or d .
u σ
Note 2 to entry: To measure encircled radiant power, using the “variable aperture method”, see ISO 11146-series.
3.3.2
beam diameter
d (z)
σ
diameter defined by using the second-
order moment of the irradiance (fluence) distribution function
dz()= 22σ ()z
σ
where the second-order moment of the irradiance distribution function E(x, y, z) of the beam z is given by
xx− zy+− yz ⋅Ex,,yz ⋅ddxy
()() ()() ()
()
∫∫
σ ()z =
Ex(),,yz ⋅ddxy
∫∫
where the first-order moments give the coordinates of the beam centroid xz() , yz()
[]
Note 1 to entry: For clarity, the term “beam diameter” is always used in combination with the symbol and its
appropriate subscript: d or d
u σ.
3.4 Beam radius
3.4.1
encircled-power beam radius
w (z)
u
radius of a circular aperture in a plane perpendicular to the beam axis
which contains u % of the total beam power (energy)
Note 1 to entry: For clarity, the term “beam radius” is always used in combination with the symbol and its appropriate
subscript: w or w .
u σ
Note 2 to entry: The beam radius is half the beam diameter d (z).
u
3.4.2
beam radius
w (z)
σ
radius defined by using the second-
order moment of the irradiance (fluence) distribution function
wz()= 2σ ()z
σ
Note 1 to entry: For clarity, the term “beam radius” is always used in combination with the symbol and its appropriate
subscript: w or w .
u σ
Note 2 to entry: The beam radius is half the beam diameter d (z).
σ
ISO/DIS 11145:2025(en)
3.5 Beam width
3.5.1
slit-transmitted-power beam width
d (z), d (z)
ux uy
width of the smallest slit aligned with the x or y transverse axes of
the irradiance (fluence) distribution function, transmitting u % of the total beam power (energy) along x or y
Note 1 to entry: For circular Gaussian beams, d and d both equal d .
95,4x 95,4y 86,5
Note 2 to entry: For clarity, the term “beam width” is always used in combination with the symbol and its appropriate
subscripts: d , d or d , d .
σx σy ux uy
Note 3 to entry: To measure beam width, using the “moving slit method”, see ISO 11146-3.
3.5.2
beam width
d (z), d (z)
σx σy
width defined by using the second-
order moment of the irradiance (fluence) distribution function along x or y
dz()= 4σ ()z
σxx
dz = 4σ z
() ()
σ yy
where the second-order moments of the irradiance distribution function E(x, y, z) of the beam at z are given by:
()xx− ()zE⋅ ()xy,,zx⋅ddy
∫∫
σ z =
()
x
Ex,,yz ⋅ddxy
()
∫∫
yy− zE⋅ xy,,zx⋅ddy
()() ()
∫∫
σ ()z =
y
Ex(),,yz ⋅ddxy
∫∫
where the first-order moments give the coordinates of the beam centroid xz , yz
[]() ()
Note 1 to entry: For clarity, the term “beam width” is always used in combination with the symbol and its appropriate
subscripts: d , d or d , d .
σx σy ux uy
Note 2 to entry: To measure beam width, using second-order moments, see ISO 11146-1.
3.5.3
principal axes
axes of the maximum and minimum beam extent
based on the second-order moments of the irradiance distribution function in a cross section of the beam
3.6 Beam cross-sectional area
3.6.1
encircled-power beam cross-sectional area
A (z)
u
smallest completely filled area containing u % of the total beam power
(energy)
Note 1 to entry: For clarity, the term “beam cross-sectional area” is always used in combination with the symbol and
its appropriate subscript: A or A .
u σ
ISO/DIS 11145:2025(en)
3.6.2
beam cross-sectional area
A (z)
σ
area of a beam with circular cross-section
π
  2
Ad= ⋅ ()z
 
σσ
4
or elliptical cross-section
π
 
Ad= ⋅ ()zd⋅ ()z
 
σσxyσ
 
Note 1 to entry: For clarity, the term “beam cross-sectional area” is always used in combination with the symbol and
its appropriate subscript: A or A .
u σ
3.6.3
beam ellipticity
ε(z)
parameter for quantifying the circularity or squareness of a irradiance (fluence) distribution at z
 
mind ()zd, ()z
σσxy
 
ε ()z =
maxdz ,dz 
() ()
σσxy
 
Note 1 to entry: It follows that 0 < ε(z) ≤ 1.
Note 2 to entry: In case of a rectangular distribution, ellipticity is often referred to as “aspect ratio”.
Note 3 to entry: In contrast to the definition given here, in literature the term “ellipticity” is sometimes related to
dz()
σ y
1− . The definition given here has been chosen to be in concordance with the same definition of ellipticity in
dz()
σx
ISO 11146-1 and ISO 13694.
3.6.4
circular irradiance distribution
irradiance distribution having a beam ellipticity ε(z) greater than or equal to 0,87 at z
3.7 Beam waist
3.7.1
beam waist
portion of a beam where the beam diameter or beam width has a local minimum
3.7.2
beam waist location
z , z , z
0x 0y 0
location where the beam widths or the beam diameters reach their minimum values along the beam axis
Note 1 to entry: A particular beam can have multiple beam waist locations.
3.7.3
astigmatic beam waist separation
Δz
a
axial distance between the beam waist locations in the orthogonal principal planes of a beam possessing
simple astigmatism
Note 1 to entry: Astigmatic beam waist separation is also known as “astigmatic difference”.
Note 2 to entry: The principal planes of the beam are defined by the principal axes of the beam.

ISO/DIS 11145:2025(en)
3.7.4
encircled-power beam waist diameter
d
u0
diameter d of the beam at the location of the beam waist z
u 0
Note 1 to entry: For clarity, the term “beam waist diameter” is always used in combination with the symbol and its
appropriate subscripts: d or d .
u0 σ0
3.7.5
beam waist diameter
d
σ0
diameter d of the beam at the location
σ
of the beam waist z
Note 1 to entry: For clarity, the term “beam waist diameter” is always used in combination with the symbol and its
appropriate subscripts: d or d .
u0 σ0
3.7.6
encircled-power beam waist radius
w
u0
radius w of the beam at the location of the beam waist z , which is half
u 0
the beam waist diameter d
u0
Note 1 to entry: For clarity, the term “beam waist radius” is always used in combination with the symbol and its
appropriate su
...