CO2 laser optics from NaCl

Sodium Chloride is used for windows, lenses and prisms where transmission in the 0.25 µm - 16 µm range is required. Because of its low absorption, Sodium Chloride is being used in high power laser systems. Polished surfaces must be protected from moisture by exposing them to only dry atmosphere or by using a heating element to keep the surfaces above ambient temperature. Sodium Chloride can be used at temperatures up to 400 °C. The material is sensitive to thermal shock. Irradiation generates color centers. Sodium Chloride is produced in large ingots by the Kyropoulos growth method. It cleaves easily. With care it can be polished to a high standard under humidity controlled conditions.

Chemical Formula	NaCl
Crystal Class	Cubic
Lattice Constant, Å	5.65
Molecular Weight	58.45
Density, g/cm³ at 293 K	2.17
Reflection Loss, % for two surfaces at 10 µm	7.5
Dielectric Constant for 10²-2.5x10¹⁰ Hz at 298 K at 358 K	5.9 6.35-5.97
Melting Temperature, K	1070
Thermal Conductivity, W/(m K) at 80 K at 289 K at 400 K	35.1 6.5 4.85
Thermal Expansion, 1/K at 75 K at 273 K at 1000 K	19.0 40.0 69.5
Specific Heat, cal/(g K) at 273 K	0.20
Debye Temperature, K	321
Bandgap, eV	9.0
Solubility, g/100 g H₂O at 273 K	35.7
Knoop Hardness	15.2 [110] 18.2 [100]
Young's Modulus, GPa	39.96
Rupture Modulus, GPa	0.00393
Shear Modulus, GPa	8.97
Bulk Modulus, GPa	24.32

Wavelength, µm	0.35	0.46	0.68	1.25	4.50	7.30	9.50	10.6	12.0	13.1	14.2	15.1	16.0
Refractive Index	1.58	1.56	1.54	1.53	1.52	1.51	1.50	1.49	1.48	1.47	1.46	1.45	1.44

Material	Sodium Chloride
Flatness	2 Lambda at 633 nm per inch
Scratch-Dig	80 - 20
Size tolerance	± 0.2 mm
Parallelism	less than 10 arc minutes
Clear aperture	90 %
Bevels	(0.2-0.5)mm x 45°

Diameter, mm	Thickness, mm	Part Number
12.7	2	W10-05
25.4	3	W10-10
38.1	4	W10-15
50.8	6	W10-20
76.2	8	W10-30
101.6	12	W10-40
Sizes up to 500 mm diameter x 60 mm thickness are available by special order.