The TABLE Data Section
Syntax:
TABLE <coating name> ANGL <angle in degrees> WAVE <wavelength 1 in micrometers> Rs Rp Ts Tp Ars Arp Ats Atp WAVE <wavelength 2 in micrometers> Rs Rp Ts Tp Ars Arp Ats Atp WAVE <wavelength 3 in micrometers> Rs Rp Ts Tp Ars Arp Ats Atp ANGL <next angle in degrees> WAVE <wavelength 1 in micrometers> Rs Rp Ts Tp Ars Arp Ats Atp WAVE <wavelength 2 in micrometers> Rs Rp Ts Tp Ars Arp Ats Atp WAVE <wavelength 3 in micrometers> Rs Rp Ts Tp Ars Arp Ats Atp
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Table coatings are similar to IDEAL coatings, except the transmission and reflection may be a function of incident angle and wavelength and may be specified separately for S and P polarizations. For multiple discrete angles of incidence and wavelengths, four intensity values are defined: Rs, Rp, Ts, and Tp; for intensity reflection and transmission and the s and p subscripts indicate the polarization state. There are also four angles (in degrees) defined: Ars, Arp, Ats, and Atp; these values define the phase angle of the R and T values so OpticStudio can compute the real and imaginary parts of the transmission and reflection. The real part is proportional to the cosine of the angle, and the imaginary part is proportional to the sine of the angle. If the angles are omitted or zero the reflection or transmission is real and no phase change is introduced by the coating. The absorption is computed from A = 1 - R - T for each polarization state. If the substrate is not a mirror and the incident index is higher than the substrate index, the phase of reflection is changed by a factor of π .
The primary purpose of the table model is to allow accurate ray tracing where the layer by layer prescription of the coating is not known or is unavailable because the coating vendor will not provide the design data.
The syntax consists of the keyword TABLE followed by the name of the coating. Table coating names may be any user defined name up to 32 characters in length, with no special characters permitted. Note that spaces are not allowed. After the TABLE keyword, blocks of data are defined for each incident angle. After each angle definition, R and T values are defined for each wavelength in the table. An example syntax would be:
TABLE MYTABLECOAT ANGL 0 WAVE 0.35 0.014 0.014 0.986 0.986 0.0 0.0 0.0 0.0 WAVE 0.70 0.013 0.013 0.987 0.987 0.0 0.0 0.0 0.0 ANGL 5 WAVE 0.35 0.015 0.015 0.985 0.985 0.0 0.0 0.0 0.0 WAVE 0.70 0.012 0.012 0.988 0.988 0.0 0.0 0.0 0.0 ANGL 45 WAVE 0.35 0.065 0.070 0.935 0.930 0.0 0.0 0.0 0.0 WAVE 0.70 0.062 0.065 0.938 0.935 0.0 0.0 0.0 0.0 ANGL 80 WAVE 0.35 0.600 0.600 0.400 0.400 0.0 0.0 0.0 0.0 WAVE 0.70 0.600 0.600 0.400 0.400 0.0 0.0 0.0 0.0
There are several very important points to note:
Angles of incidence less than the smallest angle defined will use the smallest angle data. Angles of incidence greater than the largest angle defined will use the largest angle data. Other values are linearly interpolated in cosine of the angle space. Note OpticStudio interpolates but does not extrapolate. Angles must be listed in ascending order. If data for an angle of incidence of 0.0 degrees is defined, the S and P data should be identical, since S and P are indistinguishable at normal incidence.
Angles of incidence are assumed to be in the incident media, and for coatings placed on refractive surfaces, that the incident media has a lower index of refraction than the substrate. For coatings placed on surfaces where the rays go from high index to low index (such as glass to air), the refracted angle in the low index media is used as the angle of incidence. OpticStudio assumes the phase of transmission is zero if no phase angles are defined. The phase data is angles measured in degrees if the data is provided. If the substrate is not a mirror and the incident index is higher than the substrate index, the phase of reflection is changed by a factor of π .
Wavelengths in between wavelength data points will linearly interpolate in wavelength space.
All wavelengths listed must be identical for each angle. The same ascending order values for the wavelengths is required at each angle for accurate interpolation. An error message will result if the wavelengths are not properly defined.
Generally much more than the brief set of data listed here is required for adequate accuracy. There are no limits on the number of angle and wavelength data points associated with each table coating.
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