Refractive index
The refractive index of a certain medium refers to the ratio of the speed of light in vacuum to the speed of light in the medium. The refractive index range of glass is generally between 1.4-4.0. Compared with glass optimized for infrared, the refractive index range of visible glass is smaller. For example, the refractive index of N-BK7 (a general-purpose visible glass) is 1.517, while the refractive index of germanium (a general-purpose infrared glass) is 4.003. The refractive index of an optical glass is an important property because the power of an optical surface is derived from the difference between the radius of curvature of the surface and the refractive index of the medium on either side of the surface. The non-uniformity specified by the glass manufacturer refers to the change in the refractive index of the glass. The unevenness is specified according to different levels, where the level and the unevenness are opposite to each other. As the level increases, the unevenness will decrease
Dispersion coefficient
Another material property of glass is the dispersion coefficient, which is used to quantify the amount of dispersion that glass exhibits. It is the refractive index of the material at the wavelengths of f (486.1nm), d (587.6nm) and c (656.3nm)
The dispersion coefficient value usually ranges from 25 to 65. When the dispersion coefficient of glass is greater than 55 (smaller dispersion), the glass will be regarded as crown glass, and those with a dispersion coefficient less than 50 (more dispersion) will be regarded as flint glass. Due to the dispersion, the refractive index of glass varies with wavelength. The most significant result of chromatic dispersion is that the focal length of the system will be slightly different for different light wavelengths.
laser damage threshold
The laser damage threshold refers to the maximum amount of laser power that the surface of each area can withstand before laser damage. Both pulsed lasers and continuous wave (CW) lasers have corresponding laser damage thresholds. The laser damage threshold is a very important material specification for mirrors because they are used with laser products rather than any other optical products. However, any laser-grade optical product will provide a threshold. For example, consider Ti: the rated damage threshold of a sapphire laser mirror is 0.5 J/cm2 @ 150 femtosecond pulse and 100kW/cm2 CW. This means that the energy density of the high repetitive femtosecond pulse laser that the reflector can withstand per square centimeter is 0.5J, or the energy density of the high-power CW that can be tolerated per square centimeter is 100kW. If the laser beam is concentrated in a smaller area,
You must consider taking corresponding measures to ensure that the overall threshold does not exceed the specified value. Although there are a series of other production specifications, surface specifications and material specifications, if you understand the *common optical specifications, you can significantly avoid confusion. Lenses, mirrors, windows, filters, polarizers, prisms, beamsplitters, gratings, and optical fibers have various properties. Therefore, understanding the relationship between them and how they affect the overall system performance will help You can choose the best components for integration into optical, imaging or optoelectronic applications.