What are Optical Gels?
Optical gels are a coupling agent used to match the refractive index of BK-7 glass along with other glass, and fused Silica.
Selecting the Best Optical Gel for the Application
There are different types of optical gels that work better for different uses. Below is a list of applications and the best optical gel for each.
Optical Coupling for Optical Fibers and Optical Components - There are two optical gels that reduce or eliminate internal reflectance, thus increasing transmittance of light. They do this by having a refractive index and dispersion similar to many glasses and optical plastics, and closely match the refractive index and dispersion of fused silica. The best optical gels for this are Cargille Optical Gel 0607 and Cargille Optical Gel 0608.
Mode Stripping Gel - When Cargille Optical Gel 0607 or Cargille Optical Gel 0608 is applied to a silica fiber with cladding, it removes the cladding signal. This is helpful when evaluating fiber systems that use only short fiber lengths, because the signal carried for a short distance in the cladding can be eliminated from the system and detectors will only record the signal cultivated by the fiber core. The alternate would be to physically strip away the cladding, which is both time consuming and destructive.
What is the Difference Between Optical Gel 0607 and Optical Gel 0608?
Optical Gel 0607 and Optical Gel 0608 are nearly identical in chemical composition and optics. Both gels are transparent to radiation in the visible, near infrared, and near UV. Optical Gel 0607 is thinner than Optical Gel 0608, and if you let it sit, the surface of Optical Gel 0607 will appear to be fluid. Although Optical Gel 0607 is not water soluble, it is made to "disperse" when immersed in water to facilitate cleaning. Optical Gel 0608 is specifically made for applications where water immersion WITHOUT dispersing or changing is required.
How to Minimize Ghost Images Caused by Secondary Reflections Off Lens Surface - Sub-Lux Gels are deeply black gels with refractive indices close to many common glasses. Sub-Lux gels aim to minimize ghost images caused by reflections off a lens surface. When the gel is similar to the refractive index of a glass element, light going through the glass goes gets trapped in the gel's black pigment. The gels are stable and will not evaporate, dry out, or harden. The Sub-Lux Gels are available in three refractive indices: nD=1.46, nD=1.52, and nD=1.54 at 25ºC.
Eliminate or Reduce Reflection Losses with Optical Couplant - Optical Gel 081160 nD=1.52 has the refractive index of BK-7 glass and is close to the refractive indices of other glasses. The gel is used to reduce or eliminate reflection losses. It is not recommended for Acrylic because it is slightly incompatible at elevated temperatures.
