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Using 1 dipole or multiple dipoles in core-shell emitter diodes (LEDs)


      Hi Lumerical,


      I am Yuzi Song, a PhD student at Research school of Physics in Australia National University.


      I am writing to ask you about simulating the optical properties of nanowire LED by using 1 dipole  or multiple dipoles.


      I read lots of literatures and the model provided by FDTD, in which people usually use

       (1)1dipole  and do not get the average data or (for example, Large enhancement of light extraction efficiency in AlGaN-based nanorod ultraviolet light-emitting diode structures | Discover Nano (

      (2)1dipole  and sweep different position and get the average value( for example, Micro-LED – Ansys Optics or,Optical properties of plasmonic light-emitting diodes based on flip-chip III-nitride core-shell nanowires)

      (3) random multiple dipoles (we are exploring this way)


      My question is

      (1) As dipoles in different position have impact on Purcell factor, light extraction efficiency,  is the first method above wrong?

      (2) although the second method use "sweep" to include the impact from position and then get the average value from all of the simulations, but it is still use only one dipole in 1 simulation. Considering the mechanism of core-shell nanowire LED, it is the whole active layer emits lights, so is it right to only use 1 dipole in active layer?

      (3) I am currently considering the third way, in which we set random dipoles in the active layer. But I also find that people think "Multiple dipole sources are intrinsically suited for the simulation of active layer in 3D FDTD method. However, the use of multiple dipole sources leads to non-physical interference pattern."(from  Frustrated total internal reflection in organic light-emitting diodes employing sphere cavity embedded in polystyrene (

      Is there any way to reduce or remove the influence of those "non-physical interference pattern"?


      Best regards,


    • Guilin Sun
      Ansys Employee

      I cannot comment for other's work, but the secod method is correct. 

      People believe random in space can be helpful. However how do you evaluate the spatial coherence is  a question.  Lumerical method is incoherent without questions. 

      I agree with the comment: the use of multiple dipole sources leads to non-physical interference patter

      Unfortunately it can be very challege, if not possible to remove  "non-physical interference pattern". As you read the Ansys Insight for multiple-dipoles which you also asked a few questions, when more than one dipole is inside the simulation volume they interfere with each other. This is physics, except you have used sufficient number of random dipoles sources and the result is spatially incoherent or the coherence is very low.


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