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Suprasil® 501 ArF / 502 ArF

General Product Description
Heraeus SUPRASIL® 501 ArF and 502 ArF are state of the art high purity synthetic fused silicia grades manufactured by flame hydrolysis, especially designed and optimized for 193nm immersion microlithography applications. They combine outstanding optical characteristics and exellent transmission with superior laser resistance from deep UV to near IR.
The index homogeneity is controlled and specified either in one direction (the direction of use or functional direction) or even in all three dimensions.

All synthetic fused silicia SUPRASIL® grades are practically free of bubbles and inclusions.
SUPRASIL® 501 is an optically isotropic 3D-material. It is highly homogeneous and has no striations in all three dimensions. These properties are very important for multiple axis optics such as prisms, steep lenses, beam splitters or etalons.
SUPRASIL® 502 is homogeneous in the primary functional direction. Weak striations, if any, are parallel to the major faces and do not affect the optical performance.
SUPRASIL 502 is the preferred materials for demanding optics in one directional use such as lenses, UV-laser windows, optical flats, etc.
Bubbles and Inclusions
(Bubbles and Inclusions ≤ 0.08 mm diameter are disregarded)

Bubble class :
better than 0 (as per DIN 58927 2/70)

Bubbles according to DIN ISO 10100
According to DIN ISO 10110 1/2*0.10

Refractive Index and Dispersion
Refractive Index
nC = 1.45644 at 656.3 nm
nd = 1.45852 at 587.6 nm
nF = 1.46315 at 486.1 nm
ng = 1.46671 at 435.8 nm
n = 1.50844 at 248 nm
At 22°C, 1 bar atmospheric pressure
Accuracy: ± 3 x 10-5

nF - nC = 0.00671
vd = 68,3 ± 0,3
Optical Homogeneity
Granular Structure:

Suprasil 501 ArF
In all three dimensions free from strations, i.e. better than grade A, MIL-G-174 B, or as per DIN ISO 10110 2/ -;5

Suprasil 502 ArF
In primary functional direction free from striations, i. e. grade A, MIL-G-174 B; or as per DIN ISO 10110 2/ -;5; weak striations, if any, are parallel to the major faces.

Index Homogeneity
Specified across 90% of diameter or sidelength for machined parts.

Suprasil 501 ArF
In all three dimensions guaranteed total ∆n ≤ 2 x 10-6;
with power subtracted ∆n (p.s.) ≤ 1 x 10-6;
on special request total ∆n ≤ 1 x 10-6.

Suprasil 502 ArF
In primary functional direction guaranteed total ∆n ≤ 3 · 10-6;
with power subtracted ∆n (p.s.) ≤ 1 · 10-6;
on special request total ∆n ≤ 2 · 10-6.

∆n (p.s.) (power subtracted) is calculated by subtracting from a measured ∆n distribution the proportion that gives an exactly spherical aberration of an originally plane optical phasefront. This subtraction procedure is built into most modern interferometer software as an option.
Residual Strain
≤ 2 nm/cm on clear aperture or across 90% of diameter or side length
smaller values on request
Spectral Transmittance
Typical transmission curves (including Fresnel reflection losses) for a 10 mm path lenght are shown in the figure.

Decadic Extinction Coefficient at 200 nm and at 193 nm
k200 < 0.0015 cm-1
k193 < 0.002 cm-1
Using the definition:

Transmittance T = 10-kd
with d = thickness of sample

Infrared Absorption
OH absorption bands occur at wavelengths around 1.39 µm, 2.2 µm, and 2.72 µm according to an OH content of approximately 100 ppm (weight).

With 254 nm excitation (low pressure Hg lamp and Schott UG 5 filter) and visual inspection.
Radiation Resistance
Excellent resistance to damage by high energy UV-laser radiation.
High laser damage threshold.
No degradation of visible Transmittance after exposure to Co60 γ-radiation (1.15 MeV) with 0.063 Mrad/h for 98 h.