Photonics

Photonics

About Substrate and FDTD (Z min)

    • 2212296
      Subscriber

      Hello, recently I am simulating the transmission spectrum of a metal split metal aluminum ring.

      Purpose: Transmission spectrum of light exiting through a metasurface

      Aluminum set PEC material (thickness: 0-200nm) 200nm

      Substrate refractive index 3.4 (thickness -500um - 0 ) 500um

      Light source plane light incidence (Y polarization)

      T : DFTMonitor is set at -500 um (bottom of substrate)

      FDTD : Z max : 10um Z min = ? ? ?              x y periodicity z PML

      Consider two cases

      1 Extend the substrate in the z direction -600um - 0

      T : DFTMonitor is set at -500 um

      FDTD : Z max : 10um Z min = -510 um

      2 Substrate: -500um - 0

      T : DFTMonitor is set at -500 um

      FDTD : Z max : 10um Z min = -510 um (There is a gap between the substrate and the bottom of the FDTD)

      I don't know which of the two cases is correct.

      best

    • 2212296
      Subscriber

      case1

    • 2212296
      Subscriber

      case2

    • Guilin Sun
      Ansys Employee

      Your purpose is to " Transmission spectrum of light exiting through a metasurface", so it will depend on how do you define the metasurface.

      The suggestion to include only a small portion of the substrate is to resolve the issue you experienced with no time signal in the time monitor, far below the nano-structure.

      Since the substrate is in a few source wavelengths, and it is suspended in air, you should include it to get the transmission, with much longer simulation time and smaller autoshutoff min. You will need to let the back-and-forth reflections from the substrate decay completely in order to get the accurate result.

      Please do not place the frequency-domain monitor exactly on the material surface.

      I guess you have noticed that the second simulation takes longer time compared to the 1st one.

       

      • 2212296
        Subscriber

        My purpose is to measure the spectrum after passing through the substrate (-500umto0), so the DFTMonitor is set at -500um.

        Sincerely, I don't fully understand your answer.

        You mean: the monitor needs to be placed in a vacuum? Can't be put in the material? case2 is better?

      • 2212296
        Subscriber

        include only a small portion of the substrate???

        What does this sentence mean?

        The position of the monitor can be placed at -10um, or -20um, or -500um; As long as light travels in the substrate, it is the same result???

        Because the substrate refractive index is real and does not absorb light?

    • Guilin Sun
      Ansys Employee

      No you have the signal found from the time monitor, so there is no need to do it. Instead, please enclose the whole substrate, and place the frequency domain monitot out side of the cavity substrate. As you can clearly see, when the whole substrate is enclosed in simulation the reasonance appears.

      You place the monitor in anywhere you want for a purpose.

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