Far-field of dipole emitter buried into a dielectric slab

Hi,

I am trying to simulate the far-field distribution of a dipole emitter buried within a dielectric slab but I am a bit confused about using any apodization in the field monitor and position of the field monitor to capture the near-field distribution.

The complete description of the structure is following:

It’s a few layer stack (Au/SiO2/TiO2/polymer)

at the bottom there is a 150 nm gold (Au) layer

on top of gold there is a 430 nm SiO2 layer (index, n ~ 1.45)

then a 200 nm TiO2 layer (n~ 2.35)

Finally, there is a polymer layer (thickness ~ 500 nm and index, n ~ 1.8) on top of the TiO2 layer

The dipole (TE) emitter sits deep within the polymer and close to TiO2 layer (say, 30 nm above the TiO2/Polymer interface and 470 nm below the air-polymer interface )

My Questions are

a. where should I place the field monitor for extracting the far-field? above the air-polymer interface?

b. should I use any kind of apodization filter in the field monitor as used in the case of a dipole inside a cavity?

Thanks in advance.

Salahuddin

Hello @s.nur,

Thank you for the questions.

a) Yes, to calculate the far field you should place the monitor in the air above the stack.
b) No, unlike in cavity simulations, time apodization is not necessary for this simulation.

I would recommend you take a look at the Stackdipole and FDTD simulations - halfspace dipole example to see how these types of simulations are set up. You should also consider using the STACK optical solver (also discussed in the halfspace dipole example), which uses an analytic model to calculate far field emission from a dipole in a stack. You could use the STACK solver by itself, or use both STACK and FDTD simulations and compare the results. If they are similar then this indicates that your FDTD simulation is set up properly.

I hope this helps. Let me know if you have any questions.

Hi @kjohnson,

Thanks very much for the reply. This is very helpful.

Now, I have another question :grin: … If I incorporate a nanophotonic structure, say a photonic cavity/circular grating into the TiO2 layer below the emitter. The emitter is still sitting inside the polymer but would be affect somewhat by the cavity. Would I need to use any apodization in this case to extract the far-field pattern from a field monitor positioned in the air above the stack?

Thanks,

Salahuddin

The reason we use apodization in cavity simulations is because we would like to study the cavity modes. We are not interested in studying the dipoles specifically, they are only used as a means of exciting the modes. We use apodization to ignore the transient fields from the dipoles that are not part of the modes.

In your case you are interested in studying an emitter that is modeled by the dipole, so you should not use apodization.

Thanks! That’s where I got a bit confused!

I am interested in the dipole emitter but being near the photonic structure its emission gets modified at cavity resonances. So, if I already know the resonant modes and want to study the emitter behaviour at resonances, I do not need care about/use any apodization. Am I getting it right?

Thanks again for your patience.

Salahuddin

Yes, if you want to study the emission from the dipole you should not use apodization. If you want to study the characteristics of the cavity modes specifically (resonant frequencies, Q factors, etc.), then you would use apodization.

Note that if your simulation involves resonators, you will probably need to increase the simulation time to allow the modes to decay.

Thanks very much for your answers and the clarification … This was really helpful …

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