SIST EN ISO 11254-2:2002
(Main)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 and laser-related equipment - Determination of laser-induced damage threshold of optical surfaces - Part 2: S-on-1 test (ISO 11254-2:2001)
This standard specifies a test method for determining the laser radiation induced damage threshold of optical surfaces subjected to a succession of similar laser pulses.
Laser und Laseranlagen - Bestimmung der laserinduzierten Zerstörschwelle optischer Oberflächen - Teil 2: S auf 1-Prüfung (ISO 11254-2:2001)
Dieser Teil von ISO 11254 legt ein Prüfverfahren zur Bestimmung der laserinduzierten Zerstörschwelle von optischen Oberflächen, die einer Serie gleichartiger Laserpulse ausgesetzt wurden, fest.
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)
La présente partie de l'SO 11254 spécifie une méthode d'essai pour déterminer le seuil d'endommagement causé par un rayonnement laser simple sur les surfaces optiques soumises à une succession d'impulsions laser.
Laserji in z laserji povezana oprema - Ugotavljanje praga poškodbe na optični površini, povzročene z laserjem - 2. del: Preskus S na 1 (ISO 11254-2:2001)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 11254-2:2002
01-maj-2002
/DVHUMLLQ]ODVHUMLSRYH]DQDRSUHPD8JRWDYOMDQMHSUDJDSRãNRGEHQDRSWLþQL
SRYUãLQLSRY]URþHQH]ODVHUMHPGHO 3UHVNXV6QD ,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
SIST EN ISO 11254-2:2002 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 11254-2:2002
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SIST EN ISO 11254-2:2002
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.
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SIST EN ISO 11254-2:2002
EN ISO 11254-2:2001 (E)
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).
2
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SIST EN ISO 11254-2:2002
EN ISO 11254-2:2001 (E)
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
3
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SIST EN ISO 11254-2:2002
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SIST EN ISO 11254-2:2002
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
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SIST EN ISO 11254-2:2002
ISO 11254-2:2001(E)
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ii © ISO 2001 – All rights reserved
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SIST EN ISO 11254-2:2002
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 2001 – All rights reserved iii
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SIST EN ISO 11254-2:2002
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
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SIST EN ISO 11254-2:2002
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,
4
Be, Cr, Ni) lead to severe health hazards. See annex D for further comments.
© ISO 2001 – All rights reserved v
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SIST EN ISO 11254-2:2002
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SIST EN ISO 11254-2:2002
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 2001 – All rights reserved 1
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SIST EN ISO 11254-2:2002
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:
100
2
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
22
xy�
�8
��
2
d
2
86,5
8r
H e dxdy
max
�
�� �
2
d
Q 1
���� 86,5 2
(4)
Ae�� � 2�rdr��d
T,eff 86,5
�
HH 8
max max
0
2 © ISO 2001 – All rights reserved
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SIST EN ISO 11254-2:2002
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
2
rH(,r��)rdrd
��
2
00
� ()z � (5)
��2
H(,r��)rdrd
��
00
and the definition of the beam diameter d as a function of the second moment
�
dz() �2 2�()z (6)
�
theeffective area canbeexpressedinthefollowingforms:
2
112 2
a) flat top beam:Ad����2;��d�d (7)
�d
T,eff 100 100 �
44
�
1122 2
b) Gaussian beam:Ad�� ��� ; �d (8)
��dd
T,eff 86,5 � 86,5 �
88
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 2001 – All rights reserved 3
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SIST EN ISO 11254-2:2002
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
2
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
2
E
W/cm maximum power density
max
2
F
W/cm maximum linear power density
max
2
H
J/cm maximum energy density
max
2
E
W/cm threshold power density
th
F
W/cm threshold linear power density
th
2
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
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SIST EN ISO 11254-2:2002
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 2001 – All rights reserved 5
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SIST EN ISO 11254-2:2002
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
4
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
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SIST EN ISO 11254-2:2002
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
1
2 � 5 � 5 � 6 � 10
� 5 � 5 � 6 � 10
3
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
...
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