Animation Examples

These animations were created using the new “Interactive Analysis” capability in TFCalc 3.5. There many uses for this interesting feature.

 

Wedge filter: shifting the central wavelength of a bandpass filter using the group factor

This shows how the group factor can be used to shift a design to other wavelengths. The group factor multiplies the thickness of all the layers in the group by the same factor. In this case, all the layers are in the same group. The group factor varies from 1.0 to 1.0003. This also simulates the performance of a wedge filter at different points on the filter.

Viewing the sensitivity of a bandpass filter to angle shifts

This shows how sensitive a design is to angle shifts.

Viewing the sensitivity of a bandpass filter to index shifts

This example shows how sensitive a design is to the index of the materials. Here, the low index material varies from 1.45 to 1.48. The bandwidth shift is very apparent.

Viewing the sensitivity of a bandpass filter to shifts in the index of the outside layer

This example shows how sensitive a design is to the index of the outside layer. Here, the index of the outside layer is allowed to decrease from 1.465 to 1.365, which can happen if the layer absorbs mosture.

Changing the bandwidth of a prototype bandpass filter using the variable materials factor

This example illustrates how the variable materials factor can be used to adjust the bandwidth of a prototype bandpass filter. Here the factor changes from 0.3 to 0.55.

Viewing frustrated total reflection (FTR) as a function of layer thickness

This example illustrates how frustrated total reflection (FTR) depends on thickness of the thin layer.

The phenomenon of total internal reflection (TIR) occurs when light travels from a high-index medium to a low-index medium and the incident angle is greater than the critical angle. The thin curves on the plot below show that TIR starts at about 41 degrees when the incident medium is glass (n=1.52) and the exit medium is air (n=1.0).

The phenomenon of FTR (or FTIR) occurs when light travels from a high-index medium, through a thin low-index layer, to a high-index medium. Below, the thick curves show the reflectance as the thickness of the low-index layer (air) changes from 10 to 900 nm. Note that as the layer thickness increases, the reflectance becomes closer to total at 41 degrees. That is, FTR gives way to TIR.

Viewing surface plasmon resonance (SPR) as a function of layer thickness

This example illustrates how surface plasmon resonance (SPR) can be used to measure the thickness of a “contaminant” layer.

SPR can be observed when p-polarized light travels through a high-index medium and reflects off of a thin metal layer which is next to a low-index medium (e.g., the model is Glass/Gold/Air). The incident angle is slightly higher than the critical angle of the system without the thin metal layer (Glass/Air). SPR is observed as a large change in reflectance as the incident angle increases slightly. The thickness of the metal layer must not be too small or too great; 50 nm of gold is nearly ideal.

SPR has many uses, one of which is the measurement of thin dielectric layers deposited on the metal layer. Below we show the reflectance as a layer of SiO2 is deposited on the the gold layer. Note that the angle of minimum reflectance varies by about 13 degrees as the SiO2 thickness varies from 0 to 30 nm.