|
International
Standard
ISO 8237
First edition
Optics and photonics — Optical
2024-06
materials and components —
Specification of chalcogenide glass
used in the infrared spectrum
Optique et photonique — Matériaux et composants optiques —
Spécification des verres de chalcogénure utilisés dans le spectre
infrarouge
Reference number
© ISO 2024
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and units. 3
5 Optical properties . 3
5.1 General .3
5.2 Transmittance .4
5.3 Refractive index .4
5.4 Temperature dependence of the refractive index .4
5.5 Relative partial dispersion .4
6 Tolerances . 4
6.1 General .4
6.2 Refractive index variation .5
6.3 Optical homogeneity (homogeneity of refractive index dn ) .5
λ
6.4 Striae .5
6.5 Bubbles and inclusions .6
7 Data sheet contents . 6
Bibliography . 8
iii
Foreword
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iv
Introduction
This document applies to the specification of chalcogenide glass used in the infrared spectrum. Chalcogenide
glass described in this document is transparent in the infrared region.
Chalcogenide glass has a wide range of transparency from the visible to the infrared wavelength region. This
depends on chalcogenide chemical composition. The optical properties of chalcogenide glass can provide
flexibility and further capability for IR optical system.
Nowadays, chalcogenide glass is used as a substitute material for traditional infrared materials like
germanium, silicon or zinc selenide. The market for chalcogenide glasses is rapidly expanding. However, this
new material is sometimes distributed without specifying its properties and qualities, which can confuse
users. In consideration of the rapidly increasing of market for infrared application, the definition and
standardization of chalcogenide glass for infrared optics are necessary.
v
International Standard ISO 8237:2024(en)
Optics and photonics — Optical materials and components
— Specification of chalcogenide glass used in the infrared
spectrum
1 Scope
This document defines chalcogenide glass correctly from a chemical perspective and specifies basic
characterization and reporting of optical properties of chalcogenide glass used in the infrared spectral
range from 0,78 um to 25 um
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 12123:2018, Optics and photonics — Specification of raw optical glass
ISO 15368, Optics and photonics — Measurement of reflectance of plane surfaces and transmittance of plane
parallel elements
ISO 17328, Optics and photonics — Optical materials and components — Test method for refractive index of
infrared optical materials
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology 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/
3.1
glass
inorganic product, usually obtained after melting, cooling and annealing without crystallization; including
the solid state glass before production and the glass strip obtained in production
[SOURCE: ISO 9802:2022, 3.2.1]
3.2
chalcogenide glass
glass (3.1) compound comprising of at least one chalcogen element (group 16 in the periodic table) with the
exception of oxygen
Note 1 to entry: The compositions used in chalcogenide glass are sulfur (S), selenium (Se) and tellurium (Te).
Chalcogenide glass is also sometimes called sulfide glass, selenium glass or telluride glass depending on the most
abundant composition.
Note 2 to entry: Polonium (Po) and livermorium (Lv) are not typically considered for chalcogenide compositions.
3.3
regular transmittance
ratio of the regularly transmitted part of the (whole) transmitted flux to the incident flux
[SOURCE: ISO 11382:2010, 3.1]
Note 1 to entry: Typical transmittance spectra of glass is shown in Figure 1.
Key
X wavelength, λ, in micrometre
Y transmittance, τ , in percent
r
1 transmittance spectra of sulfide glass
2 transmittance spectra of selenide glass
3 transmittance spectra of telluride glass
Figure 1 — Typical transmittance spectra of sulfide (S) glass, selenide (Se) glass and telluride (Te) glass
3.4
internal transmittance
ratio of the radiant flux to the incident radiant flux of a collimated beam that passes, at normal incidence,
through a plane parallel polished plate, excluding reflection losses at the surfaces
2 43 22 2
−−ρρ 14 +− ρρ ++ 46τρ −+ 41ρ
()
r
τ =
i
2ρτ
r
where
τ is regular transmittance;
r
τ is internal transmittance;
i
ρ is reflectance.
[SOURCE: ISO 12123:2018, 3.12]
3.5
optical homogeneity
gradual refractive index variation within a single piece of optical glass given by the difference between the
maximum and minimum values of the refractive index within the optical glass
[SOURCE: ISO 12123:2018, 3.16]
3.6
striae
short spatial range variation of refractive index in glass with typical spatial extent from below one millimetre
up to several millimetres
[SOURCE: ISO 12123:2018, 3.17]
3.7
bubble
gaseous void in the bulk optical material of generally circular cross section
Note 1 to entry: Bubbles and solid inclusions are treated the same in assessing the quality of optical glass.
[SOURCE: ISO 12123:2018, 3.19]
3.8
inclusion
localized bulk material imperfections
EXAMPLE Bubbles, striae knots, small stones, sand and crystals.
Note 1 to entry: These terms are also applicable in the given wavelength range.
[SOURCE: ISO 12123:2018, 3.18]
4 Symbols and units
For the purpose of this document, the following symbols and units apply.
λ wavelength, expressed in micrometres
n refractive index at wavelength λ
λ
P relative partial dispersion
τ spectral regular transmittance of the specimen
r
τ internal transmittance
i
5 Optical properties
5.1 General
As with general optical glass, the composition of chalcogenide glass determines its optical properties. In
addition to the measurement and reporting method of the basic properties of transmittance, refractive
index, and relative partial dispersion which are necessary to consider the use of chalcogenide glass in optical
systems, this section defines temperature dependence of the refractive index also.
5.2 Transmittance
+3
The transmittance shall be measured at 20 °C. The standard thicknesses of the specimens shall be
−1
(2 ± 0,1) mm, (5 ± 0,1) mm or (10 ± 0,2) mm. The transmittance shall be represented by a graph, with the
wavelength (or wave number) as the X-axis, and the transmittance as the Y-axis. Uncertainty (e.g. standard
uncertainty (±σ) or expanded uncertainty (±kσ) with k = 2) for the transmittance shall be provided by error
bars on the curves, or in a statement in the graph description.
The following shall be reported:
— thickness of the sample (in the case of multiple curves, with suit
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