UV fused silica for excellent thermal stability
λ/10 surface flatness and 10-5 scratch-dig
Individualy tested with Interferogram included
Slight wedge virtually eliminates internal fringes
Our fused silica interferometer flat is polished on both sides to a Λ/10 flatness with 10-5 scratch-dig surface quality. A slight 30 ±5 arc-min wedge suppresses internal fringes. This optic is delivered with an interferogram enabling use as a calibrated reference surface.
UV Grade Fused Silica is synthetic amorphous silicon dioxide of extremely high purity providing maximum transmission from 195 to 2100 nm. This non-crystalline, colorless silica glass combines a very low thermal expansion coefficient with good optical qualities, and excellent transmittance in the ultraviolet region. Transmission and homogeneity exceed those of crystalline quartz without the problems of orientation and temperature instability inherent in the crystalline form. It will not fluoresce under UV light and is resistant to radiation. For high-energy applications, the extreme purity of fused silica eliminates microscopic defect sites that could lead to laser damage.
Highly parallel flats are unsuited for use as reference elements in interferometers as reflections from both surfaces follow the same optical path toward the viewer or imaging system, resullting in undesired large period ghost fringes.
A Fizeau Interferometer may be used to test the flatness of an optical surface, by comparing its figure against the known figure of the interferometer flat.
Fabry Perot interferometers use two interferometer flats with flat surfaces facing each other to form an air spaced resonant cavity.
Material | UV Grade Fused Silica |
Surface Flatness | ≤λ/10 @ 632.8 nm over the clear aperture |
Surface Quality | 10-5 |
Clear Aperture | Central 80% of diameter |
Diameter Tolerance | +0/-0.25 mm |
Thickness Tolerance | ±0.5 mm |
Wedge | 30 ±5 arc min |
Chamfers |
25.4 mm: 0.25–0.76 mm face width x 45° ±15° 50.8 mm: 0.38–1.14 mm face width x 45° ±15° |
Cleaning |
Non-abrasive method, acetone or isopropyl alcohol on lens tissue recommended (see How to Clean Optics) |
Damage Threshold | 5 MW/cm2 CW, 10 J/cm2 with 10 nsec pulses, typical |
Dimension (mm) | |||
Model | ø A | ø B | C |
10QB20 | 25.4 | 20.3 | 9.52 |
20QB20 | 50.8 | 40.6 | 12.70 |