EN ISO 11254-2:2001

SLOVENSKI STANDARD
01-maj-2002
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SRYUãLQLSRY]URþHQH]ODVHUMHPGHO3UHVNXV6QD,62
Lasers and laser-related equipment - Determination of laser-induced damage threshold
of optical surfaces - Part 2: S-on-1 test (ISO 11254-2:2001)
Laser und Laseranlagen - Bestimmung der laserinduzierten Zerstörschwelle optischer
Oberflächen - Teil 2: S auf 1-Prüfung (ISO 11254-2:2001)
Lasers et équipements associés aux lasers - Détermination du seuil d'endommagement
provoqué par laser sur les surfaces optiques - Partie 2: Essai S sur 1 (ISO 11254-
2:2001)
Ta slovenski standard je istoveten z: EN ISO 11254-2:2001
ICS:
31.260 Optoelektronika, laserska Optoelectronics. Laser
oprema equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 11254-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
September 2001
ICS 31.260
English version
Lasers and laser-related equipment - Determination of laser-
induced damage threshold of optical surfaces - Part 2: S-on-1
test (ISO 11254-2:2001)
Lasers et équipements associés aux lasers - Détermination Laser und Laseranlagen - Bestimmung der laserinduzierten
du seuil d'endommagement provoqué par laser sur les Zerstörschwelle optischer Oberflächen - Teil 2: S auf 1-
surfaces optiques - Partie 2: Essai S sur 1 (ISO 11254- Prüfung (ISO 11254-2:2001)
2:2001)
This European Standard was approved by CEN on 15 September 2001.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2001 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 11254-2:2001 E
worldwide for CEN national Members.

CORRECTED  2002-09-18
Foreword
This document (EN ISO 11254-2:2001) has been prepared by Technical Committee ISO/TC
172 "Optics and optical instruments" in collaboration with Technical Committee CEN/TC 123
"Lasers and laser related equipment", the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication
of an identical text or by endorsement, at the latest by March 2002, and conflicting national
standards shall be withdrawn at the latest by March 2002.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium,
Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy,
Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United
Kingdom.
Endorsement notice
The text of ISO 11254-2:2001 has been approved by CEN as EN ISO 11254-2:2001 without
any modifications.
NOTE  Normative references to International Standards are listed in Annex ZA (normative).
Annex ZA
(normative)
Normative references to international publications
with their relevant European publications
This European Standard incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions
of any of these publications apply to this European Standard only when incorporated in it by
amendment or revision. For undated references the latest edition of the publication referred to
applies (including amendments).
NOTE Where an International Publication has been modified by common modifications,
indicated by (mod.), the relevant EN/HD applies.
Publication Year Title EN Year
ISO 11145 2001 Optics and optical instruments - Lasers and EN ISO 11145 2001
laser-related equipment - Vocabulary and
symbols
INTERNATIONAL ISO
STANDARD 11254-2
First edition
2001-09-15
Lasers and laser-related equipment —
Determination of laser-induced damage
threshold of optical surfaces —
Part 2:
S-on-1 test
Lasers et équipements associés aux lasers — Détermination du seuil
d'endommagement provoqué par laser sur les surfaces optiques —
Partie 2: Essai S sur 1
Reference number
ISO 11254-2:2001(E)
©
ISO 2001
ISO 11254-2:2001(E)
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ii © ISO 2001 – All rights reserved

ISO 11254-2:2001(E)
Contents Page
Foreword.iv
Introduction.v
1 Scope .1
2 Normative references .1
3 Terms, definitions and symbols.1
3.1 Terms and definitions .1
3.2 Symbols and units.4
4 Sampling.4
5 Test method.4
5.1 General.4
5.2 Principle.5
5.3 Apparatus .6
5.4 Preparation of test specimens .11
5.5 Procedure .11
6 Evaluation.11
6.1 Principle.11
6.2 Characteristic damage curve.12
6.3 Extrapolation method.13
7 Accuracy.15
8 Test report .16
Annex A (informative) Example of test report .18
Annex B (informative) Example of a measurement procedure.21
Annex C (informative) Extrapolation method for S-on-1 tests .25
Annex D (informative) Units and scaling of laser-induced damage thresholds .26
Bibliography.27
ISO 11254-2:2001(E)
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
Draft International Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this part of ISO 11254 may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 11254-2 was prepared by Technical Committee ISO/TC 172, Optics and optical
instruments, Subcommittee SC 9, Electro-optical systems.
ISO 11254 consists of the following parts, under the general title Lasers and laser-related equipment —
Dtermination of laser-induced damage threshold of optical surfaces:
� Part 1: 1-on-1 test
� Part 2: S-on-1 test
Annexes A to D of this part of ISO 11254 are for information only.
iv © ISO 2001 – All rights reserved

ISO 11254-2:2001(E)
Introduction
Repetitive laser radiation may deteriorate and damage optical surfaces at irradiation levels below those measured
for single shot damage (ISO 11254-1 refers). Besides reversible mechanisms induced by thermal heating and
distortion, irreversible damage mechanisms due to ageing, microdamage and generation or migration of defects
are observed. This part of ISO 11254 is concerned with the determination of irreversible damage of optical surfaces
under the influence of a repetitively pulsed laser beam. The degradation of the optical quality is a function of the
laser operating parameters and the optical system in which the component is placed.
In this part of ISO 11254, two evaluation methods are described for the reduction of raw data of a damage test. The
characteristic damage curve method is based on a large number of S-on-1 test sites on the optical surface of the
specimen. The characteristic damage curve comprises a set of three graphs indicating energy density values with
damage probability values of 10 %, 50 % and 90 % for a selected number of pulses. The characteristic damage
curve represents the results of a complete and extended laser-induced damage test, and it is recommended for
basic investigations in newly developed or critical laser optics.
The second method, the extrapolation method, is created from a considerably smaller number of test sites. This
method generates a distribution diagram of damage and non-damage regions for the behaviour of the damage
threshold as a function of the number of pulses per site. This diagram is of limited reliability and may be employed
for the quality control of optical laser components, which are already qualified by a complete damage test, or for the
preparation of extended damage testing.
The present state of research in laser-induced damage and ageing is not sufficient for an accurate quantitative
determination of the service life for optical components under real operating conditions. Realistic laser damage
9 11
tests adapted to industrial applications are dependent on a large number of pulses (10 to 10 pulses) and require
a disproportionate experimental expense. This part of ISO 11254 therefore also outlines a procedure for an
extrapolation of the S-on-1 threshold from the characteristic damage curve to estimate the real lifetime of an optical
component.
NOTE 1 This part of ISO 11254 is provisionally restricted to irreversible damage of optical surfaces. Laser-induced damage to
the bulk of optical components shall be considered in a revision of this part of ISO 11254.
NOTE 2 The laser-induced damage threshold (LIDT) of an optical component which is subjected to repetitive radiation can be
affected by a variety of different degradation mechanisms including contamination, thermal heating, migration or generation of
internal defects and structural changes. These mechanisms are influenced by the laser operating parameters, the environment
and the mounting conditions of the component under test. For these reasons, it is necessary to record all parameters and to
realize that the damage behaviour may differ in systems with altered operating conditions.
Safety Warning: The extrapolation of damage data may lead to bad or erroneous calculated results and to an
overestimation of the LIDT. This may in the cases of toxic materials (e.g. ZnSe, GaAs, CdTe, ThF , chalcogenides,
Be, Cr, Ni) lead to severe health hazards. See annex D for further comments.
INTERNATIONAL STANDARD ISO 11254-2:2001(E)
Lasers and laser-related equipment — Determination of laser-
induced damage threshold of optical surfaces —
Part 2:
S-on-1 test
1 Scope
This part of ISO 11254 specifies a test method for determining the laser-induced damage threshold of optical
surfaces subjected to a succession of similar laser pulses.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this part of ISO 11254. For dated references, subsequent amendments to, or revisions of, any of these publications
do not apply. However, parties to agreements based on this part of ISO 11254 are encouraged to investigate the
possibility of applying the most recent editions of the normative documents indicated below. For undated
references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain
registers of currently valid International Standards.
ISO 10110-7:1996, Optics and optical instruments — Preparation of drawings for optical elements and systems —
Part 7: Surface imperfection tolerances.
ISO 11145:1994, Optics and optical instruments — Lasers and laser-related equipment — Vocabulary and
symbols.
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this part of ISO 11254, the terms and definitions given in ISO 11145 and the following apply.
3.1.1
surface damage
any permanent laser radiation-induced change of the surface characteristics of the specimen which can be
observed by an inspection technique described within this part of ISO 11254
3.1.2
S-on-1 test
test programme that uses a series of pulses with constant energy density on each unexposed site with a short and
constant time interval between two successive pulses
NOTE The length of the time interval between the pulses of a series is given by the inverse value of the pulse repetition
rate of the laser source.
ISO 11254-2:2001(E)
3.1.3
typical pulse
pulse with temporal and spatial shapes that represent the average properties of the pulses forming the pulse series
3.1.4
minimum number of pulses
number of incident pulses causing detectable surface damage
3.1.5
threshold
highest quantity of laser radiation incident upon the optical surface for which the extrapolated probability of damage
is zero
NOTE 1 The quantity of laser radiation may be expressed in energy density H , power density E , or linear power density
th th
F , depending on the pulse duration.
th
NOTE 2 The maximum power density E of the typical pulse is given by:
max
H
max
(1)
E �
max
�
eff
3.1.6
target plane
plane tangential to the surface of the specimen at the point of intersection of the test laser beam axis with the
surface of the specimen
3.1.7
effective area
ratio of pulse energy to maximum energy density in the target plane
NOTE 1 For spatial beam profiling perpendicular to the direction of beam propagation and angles of incidence differing from
0 rad, the cosine of the angle of incidence is included in the calculation of the effective area. In this case, the effective area may
be approximated by the following formula:
Q
A � (2)
T,eff
H cos �
� �
max
NOTE 2 For the special case of a circular flat-top beam profile with diameter d , the effective area is given by:
Q Hd�
max 100 2
(3)
Ad�� ��
T,eff 100
HH
max max
For a focused Gaussian beam with a beam diameter d , the effective area is given by:
86,5
xy�
�8
��
d
86,5
8r
H e dxdy
max
�
�� �
d
Q 1
���� 86,5 2
(4)
Ae�� � 2�rdr��d
T,eff 86,5
�
HH 8
max max
2 © ISO 2001 – All rights reserved

ISO 11254-2:2001(E)
With the definition of the second moment of the energy density distribution function H(x,y,z)atthe location z,
��2
rH(,r��)rdrd
��
� ()z � (5)
��2
H(,r��)rdrd
��
and the definition of the beam diameter d as a function of the second moment
�
dz() �2 2�()z (6)
�
theeffective area canbeexpressedinthefollowingforms:
112 2
a) flat top beam:Ad����2;��d�d (7)
�d
T,eff 100 100 �
�
1122 2
b) Gaussian beam:Ad�� ��� ; �d (8)
��dd
T,eff 86,5 � 86,5 �
3.1.8
effective beam diameter
double the square root of the effective area divided by the factor�:
A
T,eff
d � 2 (9)
T,eff
�
3.1.9
effective pulse duration
ratio of pulse energy to maximum pulse power
3.1.10
characteristic damage curve
representation of the S-on-1 laser-induced damage threshold as a function of the number of pulses per site at a
specified pulse repetition rate
ISO 11254-2:2001(E)
3.2 Symbols and units
Table 1 — Symbols and units of measurement
Symbol Unit Term
� nm wavelength
�
rad angle of incidence
p degree of polarization
N
minimum number of pulses causing damage
min
N
number of pulses per site
p
N
total number of sites for the test
TS
d
mm beam diameter in the target plane
T
d
T,eff mm effective beam diameter in the target plane
A
cm effective area in the target plane
T,eff
�
ns, �s, s pulse duration
H
� ns, �s, s effective pulse duration
eff
f
p Hz pulse repetition rate
Q J pulse energy
P
pk W peak pulse power
E
W/cm maximum power density
max
F
W/cm maximum linear power density
max
H
J/cm maximum energy density
max
E
W/cm threshold power density
th
F
W/cm threshold linear power density
th
H
J/cm threshold energy density
th
P
W average power
av
4 Sampling
Either a functional component or a witness specimen shall be tested. If a witness specimen is tested, the substrate
material and surface finish shall be the same as for the component, and the witness specimen shall be coated in
the same coating run as the component. The coating run number and date shall be identified for the test
component.
5 Test method
5.1 General
For determining the S-on-1 damage threshold, extensions of the set-up and the evaluation procedure for 1-on-1
damage thresholds measurements (ISO 11245-1 refers) are necessary. However, the S-on-1 measurement facility
described in this part of ISO 11245 can be applied for 1-on-1 measurements if the on-line damage detection
system is combined with a Nomarski-type differential interference contrast microscope. It is recommended that the
on-line damage detection system should have the facility for cutting off subsequent pulses and for stopping the
pulse counter.
4 © ISO 2001 – All rights reserved

ISO 11254-2:2001(E)
5.2 Principle
The basic approach to laser damage testing is shown in Figure 1. The output of a well-characterized stable
repetitive laser is set to the desired energy or power with a variable attenuator, and delivered to the specimen
located at or near the focus of a focusing system.
Key
1 Sample compartment 5 Waveplate
2 On-line damage detector 6 Variable attenuator
3 Beam diagnostic 7 Laser system
4Focusingsystem
Figure 1 — Basic approach to S-on-1 laser damage testing
The specimen is mounted in a manipulator which is used to position different test sites in the beam and to set the
angle of incidence. The polarization state is set with an appropriate waveplate. The incident laser beam is sampled
with a beamsplitter which directs a portion of the beam to a diagnostic unit. The beam diagnostic unit permits
simultaneous determination of the total pulse energy and the spatial and temporal profiles.
The specimen is positioned at a defined location with reference to the laser beam at the specified angle of
incidence. Each test site is irradiated with pulse trains of constant energy density and repetition rate. Each test is
conducted without moving the sample, and subsequent tests are made moving the test point across the sample at
a known distance between each test site. It is recommended that the distance between each test site be greater
than three times the laser spot diameter d . During the series of tests, a sufficient number of test sites shall be
T
tested at different energy densities. The determination of the damage threshold is based on the total data and not
on the state of damage for any individual site.
This procedure is applicable to testing with all pulsed laser systems, irrespective of pulse length, repetition rate,
and wavelength. Pulse durations widely used in industrial and scientific applications are summarized and grouped
in Table 2.
ISO 11254-2:2001(E)
Table 2 — Laser groups
Group Pulse duration
1 1 ns to3ns
2 10nsto30ns
3 1 �sto3 �s
200 �sto1000 �s
5 to be specified
Repetition rate classes widely used in industrial and scientific applications are given in Table 3. Lasers of these
classes are recommended for S-on-1 tests. Pulse repetition rates other than those specified in Table 3 are allowed
for the purposes of this part of ISO 11254. The pulse repetition rate classes are permitted in conjunction with every
possible laser group. The pulse duration and the pulse repetition rate of the test laser shall be documented in the
test report.
Laser-induced damage threshold values are dependent on the operating parameters of the laser system employed
for testing. For a comparison of threshold data under slightly different operating conditions, scaling laws, which are
based on modelling of experimental data, may be used. Safety aspects shall be considered for the application of
scaling laws to hazardous materials.
Table 3 — Repetition rate classes
Pulse repetition rate f in Hz
Class
p
A1
B10
C30
D 100
E 300
F 1 000
G to be specified
5.3 Apparatus
The test facility consists of individual sections with specific functions.
5.3.1 Laser
A laser delivering pulses with a reproducible near-Gaussian or near-flat-top spatial profile is required. The temporal
profile of the pulses is monitored during the measurement. Pulse trains containing pulses with a maximum power
density exceeding the variation of E in Table 4 shall be rejected for the evaluation procedure. The pulse
max
repetition rate shall be constant within an error margin of � 1 %. For the different laser groups, the maximum
allowable variations of the pulse parameters are compiled in Table 4. As a minimum specification of a laser system
not included in rows 1 to 4 in Table 2, the pulse-to-pulse variation of the maximum power density shall be less than
� 20 %. Stability criteria for the beam parameters shall be determined and documented in an error budget.
6 © ISO 2001 – All rights reserved

ISO 11254-2:2001(E)
Table 4 — Maximum percentage variation of laser parameters and corresponding percentage variation of
maximum pulse power density E
max
Laser group Pulse energy Pulse duration Effective area Power density
A E
Q �
T,eff max
H
� 5 � 10 � 10 � 15
2 � 5 � 5 � 6 � 10
� 5 � 5 � 6 � 10
4 � 5 � 5 � 6 � 10
5.3.2 Variable attenuator and beam delivery system
The laser output shall be attenuated to the required level with an external variable attenuator that is free of drifts in
transmissivity and imaging properties.
The beam delivery system and the attenuator shall not affect the properties of the laser beam in a manner
inconsistent with the tolerances given in 5.3.1. In particular, the polarization state of the laser beam shall not be
altered by the beam delivery system.
5.3.3 Focusing system
The arrangement of the focusing system should be adapted to the special requirements of the laser system and to
the intended beam profile in the target plane. The specific arrangement and the parameters of the focussing
system shall be documented in the test report. The specifications of the active area and the energy density shall be
referred to the location of the test surface.
For Gaussian beams, it is advisable to select an aperture of the focusing system which amounts to not less than
three times the beam diameter at the entrance of the focusing system. A minimum effective f-number of 50 and a
beam diameter in the target plane not less than 0,8 mm are recommended. The target plane shall be located at or
near the focal waist formed by the focusing system. For Groups 3 to 5, the beam diameter may be reduced
depending on the power density necessary, but should not be smaller than 0,2 mm. In such cases the effective
f-number may be reduced below a value of 50.
For near-flat-top laser beams, it is advisable to position the test surface in the image plane of the focusing system
with a focal length� 0,2 m that forms an image of a suitable aperture in the optical path.
Coherence effects in specimens with parallel surfaces can occur and affect the measurement. These effects shall
be eliminated by appropriate techniques, such as wedging or tilting of the specimen. The application of a highly
converging beam is also a practical method for removing coherence effects in the specimen.
5.3.4 Specimen holder
The test station shall be equipped with a manipulator which allows for a precise placement of the test sites on the
specimen with an accuracy sufficient for the specimen size.
5.3.5 Damage detection
A microscope technique shall be used to inspect the surface before and after the test. The investigations shall be
made with an incident light microscope having Nomarski-type differential interference contrast. A magnification in
the range from � 100 to� 150 shall be used.
NOTE 1 For routine inspection and objective measurement of laser damage, an image analyser may be attached to the
microscope.
ISO 11254-2:2001(E)
An appropriate on-line damage detection system shall be installed to evaluate the state of the surface under test.
After detection of damage, the minimum number of pulses N shall be recorded, and the measurement for the
min
next site shall be started.
NOTE 2 For S-on-1 damage testing, the detection limit of the damage monitor is not critical due to the accumulative
behaviour of the surface mechanisms. For on-line damage detection, any appropriate technique may be used. Techniques
suited to this purpose are, for instance, on-line microscopic techniques, photoacoustic and photothermal detection, as well as
scatter measurements using a separate laser or radiation from the damaging laser.
Key
1 Laser 4 Detector
2 Beam preparation system 5 Negative aperture
3 Test beam 6 Test sample
Figure 2 — Typical set-up for an on-line scatter measurement system
NOTE 3 For example, the measurement of radiation scattered by the optical surface may be applied for damage detection. A
typical set-up for on-line scatter measurements is given in Figure 2. A laser with excellent pointing stability and minimum
intensity fluctuations is used as radiation source. The laser light is refined by a beam preparation system that normally consists
of telescope systems with apertures, spatial filters and optical components for modulating the laser power density. After beam
preparation, the laser beam is focused onto the actual site of the specimen under damage test. The scattered radiation is
collected by a lens and detected by a photodetector. The fraction of the laser beam reflected by the specimen surface is cut out
by a negative aperture. To achieve high sensitivity and low interference with other light sources in the environment of the set-up,
phase sensitive detection techniques and an interference filter for the laser wavelength are recommended.
5.3.6 Beam diagnostics
5.3.6.1 Total pulse energy and average power
The diagnostic package shall be equipped with a calibrated detector to measure the pulse energy delivered to the
target plane for each individual pulse. This instrument shall be traceable to a national standard with an absolute
uncertainty of � 5 % or better. For laser systems with high repetition frequencies, the total pulse energy may be
determined by measuring the average power, P , and the pulse repetition rate, f . In this case, the pulse energy,
av p
Q,is given by:
8 © ISO 2001 – All rights reserved

ISO 11254-2:2001(E)
P
av
Q � (10)
f
p
5.3.6.2 Temporal profile
The diagnostic package shall include suitable instrumentation for analysing the temporal profile of the laser to
determine the pulse duration. The temporal profile shall be integrated to determine the ratio of total pulse energy,
Q, to peak pulse power, P . This ratio is called the effective pulse duration� :
pk eff
1/ f p
Pt()dt
�
Q
�� � (11)
eff
PP
pk pk
For lasers of the Groups 1 to 4, upper limits for the temporal resolution of the pulse duration measurement are
defined in Table 5. For lasers not included in Table 5, the upper limit of the temporal resolution shall not exceed
10 % of the effective pulse duration.
Table 5 — Upper limits for the temporal resolution of the pulse duration measurement
Group Temporal resolution
1 100 ps
21ns
3 100 ns
4 10 �s
5.3.6.3 Spatial profile
In all cases, the spatial profile shall be analysed in the target plane or an equivalent plane. The diagnostic package
shall be equipped with instrumentation to measure the two dimensional spatial profile with a spatial resolution of
� 1,5 % of the beam diameter or better.
The maximum energy density of the beam shall be determined as follows:
The two dimensional profile shall be integrated to determine the ratio of total pulse energy, Q, to maximum energy
density, H . This ratio is called the effective area A .
max T,eff
��
Hx(,y)dxdy
��
Q
�� ��
A �� (12)
T,eff
HH
max max
The maximum energy density, H , may be expressed in terms of total pulse energy or average power and pulse
max,
repetition rate:
P
Q
av
H �� (13)
max
A Af
T,eff T,eff p
ISO 11254-2:2001(E)
5.3.6.4 Typical pulse
For the determination of the spatial profile of the typical pulse, a significant fraction of the number of pulses used for
an individual site shall be recorded by the spatial profiling system. The spatial profile of the typical pulse is defined
by the average distribution of the power density recorded during the measurement cycle for an individual site. The
temporal profile and the energy of the typical pulse are given by the corresponding average data of all pulses
employed for testing of an individual site on the test surface. The test report shall contain a depiction of the
temporal and spatial profile of the typical pulse.
NOTE For the evaluation of the temporal profile, the power, P (t ), of the laser may be determined at equally spaced time
j i
coordinates, t , for every pulse. The position of the pulse in a sequence of N pulses per testing site is identified by the counting
i p
variable j. The sampling of each pulse shall be started at the first time coordinate t with a power that differs from zero. On the
basis of this measurement technique, the temporal profile P (t ) of the typical pulse can be calculated by the average of the
tp i
pulses forming a testing sequence of N pulses:
p
N
p
Pt � P t (14)
�� ��
tpij�i
N
p
j � 0
The energy of the typical pulse may be expressed by the sum of the energy contents assigned to time intervals t � t – t .
i+1 i
N
s
QP��tt (15)
��
tp � tp i
i � 0
where N is the number of time intervals necessary for describing the complete temporal shape of the typical pulse, the average
s
power, P , expected for an ideal damage test is given by
av,id
PQ� f (16)
av,id tp p
By relating the average power calculated from the energy of the typical pulse to the measured average power, P , the accuracy
av
and stability of the laser may be evaluated. The stability of the spatial profile can be assessed by recording the temporal
behaviour of the local intensity at selected positions in the spatial beam profile.
5.3.6.5 Test parameters
The testing equipment shall be characterized by the following parameters:
a) wavelength, ��
b) angle of incidence, � ;
c) degree of polarisation, p;
d) pulse repetition rate, f ;
p
e) beam diameter of the typical pulse in the target plane, d ;
T
f) effective beam diameter of the typical pulse in the target plane, d ;
T,eff
g) pulse duration of the typical pulse,� ;
H
h) effective pulse duration of the typical pulse, � ;
eff
i) number of pulses per site, N ;
p
j) total number of sites per test, N .
Ts
10 © ISO 2001 – All rights reserved

ISO 11254-2:2001(E)
5.4 Preparation of test specimens
Wavelength, angle of incidence and polarization of the laser radiation as used in the test shall be in accordance
with the specifications by the manufacturer for normal use. If ranges are given for the values of these parameters,
an arbitrary combination of wavelength, angle of incidence and polarization within these ranges may be used.
Storage, cleaning and preparation of the specimens is done according to the specimen specifications by the
manufacturer for normal use.
In the absence of manufacturer-specified instructions, use the following procedure.
a) Store the specimen at less than 50 % relative humidity for 24 h prior to testing. Handle the specimen by the
non-optical surfaces only.
b) Before testing, carry out a microscopic evaluation of surface quality and cleanliness in accordance with
ISO 10110-7 using a Nomarski/darkfield microscope at 150� magnification or higher.
c) If contaminants are observed on the specimen, the surface shall be cleaned. The cleaning procedure shall be
documented. If the contaminants are not removable, document them by photographic and/or electronic means
before testing.
d) Inspect the test site for dust particles during irradiation. The test environment shall be clean filtered air of less
than 50 % relative humidity and shall be documented.
e) The test sites shall be in a defined and reproducible arrangement. Refer the test grid to fixed reference points
on the specimen. It is acceptable to make marks at known locations on the specimen as reference points only
after testing is completed and before the specimen is removed from the specimen positioner.
NOTE It is usually possible to use one or more large damage spots as reference points, rather than potentially
contaminating the surface of the specimen. This is preferable if there is any likelihood of having to make further tests on the
specimen.
5.5 Procedure
An unexposed test site is positioned into the beam and irradiated by a series of N pulses with a selected energy,
p
Q ,of the typical pulse. If damage is observed by the on-line damage detection system before the series of N
tp p
pulses is completed, stop the irradiation of the site and record the minimum number of pulses N . Repeat this
min
procedure for different energy densities of the typical pulse. The number of pulses, N , shall be constant for the
p
entire test procedure and shall be selected such that the specific laser-induced damage behaviour of the specimen
is registered by the S-on-1 test.
6 Evaluation
6.1 Principle
After the inspection by the microscope technique (see 5.3.5), the result of the described S-on-1 test programme is
a file of data points of the type
(Q , N ) N u N in case of damage
tp min min p
(Q , N ) in case of no detectable damage
tp p
The evaluation of the data obtained (see Figure 3) may be performed by using the characteristic damage curve
(see 6.2) or the extrapolation method (see 6.3). The method of the characteristic damage curve allows for a precise
determination of the laser-induced damage threshold on the basis of an experimental procedure that is practicable
only for numbers N of shots below 10 per site. Besides this accurate technique, which should be used for
p
ISO 11254-2:2001(E)
fundamental investigations and for testing prototype components, the extrapolation method is a practical technique
to estimate the S-on-1 threshold for a large number of pulses.
6.2 Characteristic damage curve
Apply the procedure for the S-on-1 damage threshold (see 5.5) and record the resulting file of data points. For an
evaluation with sufficient significance, a minimum number, N , of sites shall be tested for each energy value, Q ,
ms tp
of the typical pulse. This minimum number of sites, N , can be approximated by the relation
ms
��
NN��5int (1�log() (17)
ms p
��
The range of typical pulse energies, Q , employed must be sufficiently broad to include points of zero damage
tp
probability as well as points of 100 % damage probability.
Damage probability values for a defined number, N, of pulses and specified energy value, Q, are calculated on the
basis of the following data reduction technique:
The energy scale is divided into a series of intervals (Q –�Q, Q��Q) covering the energy range accessible by the
experimental set-up. For the calculation of damage probability for a certain energy value, Q, and for a selected
number, N, of pulses, data points with Q (Q –�Q, Q��Q) are selected from the file of data points. Data points
tp
with N u N correspond to sites damaged, meanwhile data points with N � N or N W N correspond to sites not
min min p
damaged during the test. The damage probability for the energy, Q, is calculated by the ratio of the number of data
points corresponding to damaged sites with respect to the total number of data points considered for the
evaluation.
NOTE 1 The value of �Q is chosen such that a significant fraction of data points is available for a distinct interval
(Q – �Q, Q��Q). The value Q is kept constant during the evaluation procedure, and it determines the statistical error of the
threshold values. An example of an efficient measurement procedure and an adapted selection of the parameters is given in
annex B.
This procedure is repeated for other energy values, Q, to generate a data set of damage probability values for the
selected number, N, of pulses. The resulting data set represents discrete points of a damage probability curve
which is plotted versus the energy of the typical pulse. From this curve, energy values Q , Q , and Q are
10 50 90
deduced for the corresponding damage probability values of 10 %, 50 %, and 90 % by extrapolation.
A linear extrapolation involving the two data points next to the targeted damage probability is sufficient. If an
experimental basis with a large number of data points is available, more sophisticated extrapolation methods are
permitted. The extrapolation procedure shall be documented in the test report.
For the determination of the laser-induced damage threshold, the damage probability curve shall be linearly
extrapolated to a damage probability of zero, and the resulting threshold energy value shall be converted to the
units of threshold energy density, H , threshold power density E , or linear threshold power density, F (see
th th th
5.3.6.3 and 3.1.5).
If an experimental basis with a large number of data points is available, more sophisticated extrapolation methods
are permitted for the determination of the damage threshold. The extrapolation procedure shall be documented in
the test report.
12 © ISO 2001 – All rights reserved

ISO 11254-2:2001(E)
Key
o Undamaged
x Damaged
NOTE Data points corresponding to damaged spots are represented by “�”. Undamaged spots are represented by “o”.The
evaluation procedure for the damage probability method is illustrated by the interval (Q – �Q, Q��Q) marked in the diagram.
More than one point may occur for a specific data pair (Q , N )or(Q , N ) during the experiment. The number of points for a
tp p tp mi
...