Infrared Window Materials

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Infrared Window Materials

(graphs updated 3 July 06 - MCM)
Window Selection Guide
Material Range (cm^-1) Refractive Index
(at 2 µm) Mid-IR
%T Graph Properties

AgBr 22,000-286 2.30 A soft crystal; insoluble in water; darkens upon exposure to UV radiation; will cold flow.

AgCl 10,000-360 2.07 Soft crystal that is insoluble in water; darkens upon exposure to UV radiation; will cold flow.

Al₂O₃ (Sapphire) 50,000-1,650 1.7 Glass-like. Sapphire (Al₂O₃) is an extremely hard material which is useful for UV, NIR and IR applications through 5 microns.

AMTIR
(GeAsSe Glass) 11,000-625 2.5 AMTIR (Amorphous Material Transmitting IR) is a glass; insoluble in water, resistant to corrosion.

BaF₂ 67,000-740 1.46 A hard, brittle crystal; insoluble in water; good resistance to fluorine and fluorides; no fog.

CaF₂ 77,000-1,110 1.42 A strong crystal; resists most acids and alkalis; withstands high pressure; insoluble in water; no fog.

CdTe 20,000-400 2.67 Lower thermal conductity than ZnSe (used with CO₂ lasers). Attacked by oxidizers. Also known as Irtran-6.

Chalcogenide
(AsSeTe glass) 4,000-900 2.8 Good for Mid-IR fiber optics; chemically inert.

CsI 40,000-200 1.74 Soft crystal; soluble in water; hydroscopic; offers an extended transmission range. Because this material is so soft and extremely hygroscopic, it is very difficult to polish.

Diamond 25,000-33 2.37 Phonon bands around 1900-2600, except in Type IIa diamonds. Very useful for high-pressure or corrosive work.

GaAs 7,000-650 3.33 Hard crystal, can be made amorphous

Ge 5,500-600 4.00 A hard, brittle crystal; insoluble in water; well suited for ATR.

Irtran-1 (see MgF₂)
Irtran-2 (see ZnS)
Irtran-3 (see CaF₂)
Irtran-4 (see ZnSe)
Irtran-5 (see MgO)
Irtran-6 (see CdTe) (Irtran is a registered trademark of the Eastman Kodak Company)

KBr 40,000-400 1.53 Very soft, water soluble crystal; low cost and good transmission range; fogs.

KRS-5
(Thallium Bromide-Iodide) 20,000-250 2.37 A soft crystal, deforms under pressure; good ATR material. Soluble in bases and insoluble in acids. Toxic.

LiF 95,000-1,700 1.4 Best VUV transmitter available

MgF₂ 87,000-1,250 1.35

NaCl 40,000-625 1.52 Very soft, water soluble crystal; low cost and good transmission range; fogs.

Polyethylene
(high density) 600-30 1.54 Excellent for Far-IR, very cheap, attacked by few solvents, difficult to clean

Pyrex 30,000-4,000 1.473 Labware glass

Si 83,300-660 300-0 (depends on doping) 3.40 A hard and brittle crystal; inert; ideal material for far-IR.

SiO₂ (Quartz) 65,000-2,700 1.4 A hard crystal, clear in the visible

ZnS
(Cleartran) 17,000-833 2.2 A water-free form of ZnS. Insoluble in water. Also known as Irtran-2

ZnSe 17,000-720 2.2 A hard and brittle crystal; inert; ideal material for ATR. Also known as Irtran-1.

Window Selection Guide
Material	Range (cm^-1)	Refractive Index (at 2 µm)	Mid-IR %T Graph	Properties
AgBr	22,000-286	2.30		A soft crystal; insoluble in water; darkens upon exposure to UV radiation; will cold flow.
AgCl	10,000-360	2.07		Soft crystal that is insoluble in water; darkens upon exposure to UV radiation; will cold flow.
Al₂O₃ (Sapphire)	50,000-1,650	1.7		Glass-like. Sapphire (Al₂O₃) is an extremely hard material which is useful for UV, NIR and IR applications through 5 microns.
AMTIR (GeAsSe Glass)	11,000-625	2.5		AMTIR (Amorphous Material Transmitting IR) is a glass; insoluble in water, resistant to corrosion.
BaF₂	67,000-740	1.46		A hard, brittle crystal; insoluble in water; good resistance to fluorine and fluorides; no fog.
CaF₂	77,000-1,110	1.42		A strong crystal; resists most acids and alkalis; withstands high pressure; insoluble in water; no fog.
CdTe	20,000-400	2.67		Lower thermal conductity than ZnSe (used with CO₂ lasers). Attacked by oxidizers. Also known as Irtran-6.
Chalcogenide (AsSeTe glass)	4,000-900	2.8		Good for Mid-IR fiber optics; chemically inert.
CsI	40,000-200	1.74		Soft crystal; soluble in water; hydroscopic; offers an extended transmission range. Because this material is so soft and extremely hygroscopic, it is very difficult to polish.
Diamond	25,000-33	2.37		Phonon bands around 1900-2600, except in Type IIa diamonds. Very useful for high-pressure or corrosive work.
GaAs	7,000-650	3.33		Hard crystal, can be made amorphous
Ge	5,500-600	4.00		A hard, brittle crystal; insoluble in water; well suited for ATR.
Irtran-1 (see MgF₂) Irtran-2 (see ZnS) Irtran-3 (see CaF₂) Irtran-4 (see ZnSe) Irtran-5 (see MgO) Irtran-6 (see CdTe)	(Irtran is a registered trademark of the Eastman Kodak Company)
KBr	40,000-400	1.53		Very soft, water soluble crystal; low cost and good transmission range; fogs.
KRS-5 (Thallium Bromide-Iodide)	20,000-250	2.37		A soft crystal, deforms under pressure; good ATR material. Soluble in bases and insoluble in acids. Toxic.
LiF	95,000-1,700	1.4		Best VUV transmitter available
MgF₂	87,000-1,250	1.35
NaCl	40,000-625	1.52		Very soft, water soluble crystal; low cost and good transmission range; fogs.
Polyethylene (high density)	600-30	1.54		Excellent for Far-IR, very cheap, attacked by few solvents, difficult to clean
Pyrex	30,000-4,000	1.473		Labware glass
Si	83,300-660 300-0 (depends on doping)	3.40		A hard and brittle crystal; inert; ideal material for far-IR.
SiO₂ (Quartz)	65,000-2,700	1.4		A hard crystal, clear in the visible
ZnS (Cleartran)	17,000-833	2.2		A water-free form of ZnS. Insoluble in water. Also known as Irtran-2
ZnSe	17,000-720	2.2		A hard and brittle crystal; inert; ideal material for ATR. Also known as Irtran-1.

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