Learning Forum

[Giovanni Piscopo]

Hello everyone, 

I hope you are doing well.

I'm having some issues in calculating the Q factor of a metasurface exploiting the bound states in the continuum.

The metasurface I'm woking in is shown in the picture. Basically it consisit of a 2D array of etched crosses on a 200 nm thick germanium layer (the substrate is a bulk layer of calcium fluoride).

The main problem I'm having is the many hours required for calculating the transmittance spectrum. However since I'm more interested in the actual value of the resonant wavelength as well as the Q factor, I wanted to exploit the high Q factor monitor present in lumerical.

In particular I know that in the wavelength range betweed 4.3 um and 5 um there shoud be two fano resonances however I'm not sure how and where to place the Q factor monitor. 

In particular, should the x, y and z, span be the actual dimensions of the unit cell or only of the cross? And what values shoud nx, ny and nz have?

Thank you in advance for the answer.

I wish you a good day.

Giovanni

[Guilin Sun]

this is a good question:h

if you know the mode profile, you can place the monitor to where shows strong intensity.

If you do not know the mode profile, you will need place the time  monitors randomly in space, in order NOT to miss the strong resonant mode. I

You may set the analysis group close to the boundaries.