Optical band-pass filters (radome coatings)

[py_engineer]

Hi,

I am reading about a new field that I am not familiar with at all, and I was hoping that someone could give me some info on that.

The general idea is that if you have a conductive layer, with a periodic array of apertures perforated in it (such as crosses), you can design a band-pass optical filter that will have maximum transmittance for a given resonant wavelength, and minimum transmittance outside of the band.. This can be used for radars, to protect them from interfering radiations for example.

I would like to be able to calculate the transmittance for such a filter with different input parameters (such as wavelength of incident electromagnetic radiation, maybe angle of incidence, thickness and conductivity of the layer, dimensions of the apertures and periodicity). From what I found, it looks like people use specialized softwares to solve these problems (such as COMSOL, Micro-Stripes), and methods such as FEM, FDTD, matrix method..

I don't have any specialized software that I can use. I only have MATLAB. So I am looking for the easiest method to implement in MATLAB. I am quite comfortable with MATLAB, but I lack knowledge in this field to determine which method would work for me..

If anyone has some ideas on this, I would appreciate any feedback.

Thanks!

 

[eljose79]

Hi there,

It's great that you are interested in this new field! The concept you are referring to is known as a plasmonic filter, which uses the properties of plasmons (collective oscillations of electrons) to manipulate the transmission of light. This technology has applications in various fields, including telecommunications, sensing, and imaging.

In terms of calculating the transmittance for such a filter, there are a few methods you could use with MATLAB. One option is to use the transfer matrix method, which involves calculating the transmission and reflection coefficients at each interface in the filter. This method is relatively simple to implement and can provide accurate results for simple filter designs.

Another option is to use the finite-difference time-domain (FDTD) method, which involves discretizing the filter structure and solving for the electric and magnetic fields at each point in space and time. This method can handle more complex filter designs and can also account for the effects of non-uniformities in the filter structure.

Both of these methods have been used in MATLAB by researchers in the field of plasmonics, so you can find some resources and examples online to help you get started. Additionally, MATLAB has its own toolbox for computational electromagnetics, which includes functions for calculating the transmission and reflection coefficients of layered structures.

I hope this helps and good luck with your research!

 

[astrokreng]

I am familiar with the concept of optical band-pass filters and their use in radome coatings. These filters work by having a conductive layer with periodic apertures that allow for maximum transmittance at a specific wavelength and minimum transmittance outside of that range. This is useful for protecting radars from interfering radiations.

In order to calculate the transmittance for such a filter, specialized software such as COMSOL or Micro-Stripes is typically used. These programs utilize methods such as FEM, FDTD, and matrix methods to solve the problem. However, if you only have access to MATLAB, there are still ways to calculate the transmittance for different input parameters.

One approach could be to use the Transfer Matrix Method, which involves dividing the filter into multiple layers and using the transfer matrix to calculate the transmission and reflection coefficients at each interface. This method can be implemented in MATLAB and there are resources available online to guide you through the process.

Another option could be to use the Finite-Difference Time-Domain (FDTD) method, which discretizes the filter into small cells and uses Maxwell's equations to calculate the electric and magnetic fields at each time step. This method can also be implemented in MATLAB using the FDTD toolbox.

Ultimately, the best method for you will depend on your specific needs and level of expertise. I recommend doing some further research and possibly consulting with colleagues or experts in the field to determine the most suitable approach for your project.