Optical Gel

▶ Optical Gel nD 1.46

Optical Coupling Uses: Optical Gels nD 1.46 Codes 0607 and 0608 have two primary uses. The first use is as an optical coupling for optical fibers and optical components. They reduce or eliminate internal reflectance thus increasing transmittance of light; they do this by having a refractive index and dispersion that is similar to many glasses and optical plastics, and closely matches the refractive index and dispersion of fused silica.

Mode Stripping Gel Uses: Another primary use is as a mode stripping gel. When one of the gels is coated on a silica fiber that has cladding, it will remove the signal from the cladding. This is useful when evaluating fiber systems; using only short fiber lengths, in that the signal that is carried for a short distance in the cladding can be eliminated from the system and detectors will record only the signal propagated by the fiber core. This is quicker and easier than mechanically stripping away the cladding and is non-destructive.

Properties: These gels have several very desirable properties. They are transparent to radiation in the near UV, the visible, and the near infrared. We know of no other liquids, gels, or greases with significantly better transmittance. Each has wide temperature stability. Freezing points are below -67°C and boiling point exceeds 400°C. This means a more stable refractive index than some other liquid, gel or grease couplants.

Optical Gel Code 0607, although not water soluble, is made to “disperse” when immersed in water to facilitate cleaning.

Optical Gel Code 0608 was specially made not to “disperse” in water, for applications where water immersion without dispersing or changing is required.

▶ Optical Gel nD 1.52

Optical Gel Code 081160 has the refractive index of BK-7 glass and is close to the refractive index of other frequently used glasses. As an optical couplant, it is used to reduce or eliminate reflection losses. It is not recommended for use with Acrylic as it is slightly incompatible at elevated temperatures. It is normally opalescent / translucent but is clear in thin layers as it is normally used. It is useable over a wide range of temperatures; freezing point is less than 45°C, boiling point is greater than 370°C.

▶ Sub-Lux Gels

Sub-Lux Gels are profoundly black gels with refractive indices close to many common glasses. The purpose of each gel is to minimize ghost images caused by secondary reflections off of a lens surface. When the gel is near the refractive index of a glass element, light going through the glass goes into the gel and is trapped by absorption in sub-micron particles of black pigment.

The gels are very stable and will not harden, dry out, or evaporate. They are available in 4 ounce bottles in three refractive indices: nD= 1.46, 1.52, and 1.54 at 25°C.