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By careful choice of the type and thickness of the dielectric layers, one can design an optical coating with specified reflectivity at different wavelengths of light. Dielectric mirrors are also used to produce ultra-high reflectivity mirrors: values of 99.999% or better over a narrow range of wavelengths can be produced using special techniques.
For TE and TM incidence we have the reflection spectra of a DBR stack, corresponding to a 6 layer stack of dielectric contrast of 11.5, between an air and dielectric layers. The thicknesses of the air and dielectric layers are 0.8 and 0.2 of the period, respectively. The wavelength in the figures below, corresponds to multiples of the cell period.
A distributed Bragg reflector laser (DBR) is a type of single frequency laser diode. Other practical types of single frequency laser diodes include DFB lasers and external cavity diode lasers. A fourth type, the cleaved-coupled-cavity laser has not proven to be commercially viable. VCSELs are also single frequency devices. [1]
A fiber Bragg grating (FBG) is a type of distributed Bragg reflector constructed in a short segment of optical fiber that reflects particular wavelengths of light and transmits all others. This is achieved by creating a periodic variation in the refractive index of the fiber core, which generates a wavelength-specific dielectric mirror .
Dielectric constant, [2] ε r: 10.5 ε 0 at 20 °C Bond strength? Bond length? Bond angle? Magnetic susceptibility? Surface tension [3] 40.05 mN/m at 10 °C 38.75 mN/m at 20 °C 28.4 mN/m at 100 °C Viscosity [4] 1.1322 mPa·s at 0 °C 0.8385 mPa·s at 20 °C 0.6523 mPa·s at 40 °C 0.4357 mPa·s at 80 °C
Another type is the high-reflector coating, which can be used to produce mirrors that reflect greater than 99.99% of the light that falls on them. More complex optical coatings exhibit high reflection over some range of wavelengths , and anti-reflection over another range, allowing the production of dichroic thin-film filters .
A chirped mirror is a dielectric mirror with chirped spaces—spaces of varying depth designed to reflect varying wavelengths of lights—between the dielectric layers (stack). Chirped mirrors are used in applications like lasers to reflect a wider range of light wavelengths than ordinary dielectric mirrors, or to compensate for the dispersion ...
Dielectric spectroscopy (which falls in a subcategory of the impedance spectroscopy) measures the dielectric properties of a medium as a function of frequency. [2] [3