Learning Forum

[jiglesi1]

Greetings,

I am running a thin film analysis using the thin film lnP and I am trying to reach close to 100% transmission (<0.1% reflection) at 1.5 um. I read that changing the film thickness can help you to acheive those results but when I change the thickness of the film, I see no changes in my transmission and refledtion plots. I changed thie thickness of the lnP rectangle z min to z max fron -0.18um through 0.18um to 0 to 0.1 um. Can anyone advice what  I am doing wrong and how I may change the thickness of lnP rectangle to minimize my reflection? I attached my current plots and thickness values. Thank you in advance!

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[jiglesi1]

I resolved this issue and figured out I was adjusting the wrong dimension on the lnP film rectangle to change my reflection plots.  So does that mean once I get it closer to 0% reflectivity, the marker on the y axis in respect to the reflection will be closer to the 0 mark on the y axis correct? I am not sure what the y marker actually repreesnts since there are no units on it. This is also in respect to lambda at 1.5um. Thanks!

[Guilin Sun]

Good to know you have resolved the first issue.

You can find the min of the transmission or reflection. For example:

R=transmission("monitor_1_1");

f=getdata("monitor_1_1","f");

Rmin=min(R);

nR=find(R,Rmin);

fmin=f(nR);

?c/fmin*1e6; # wavelength which shows the min reflection

plot(c/f*1e6,R,"w um","R","Reflection");

so you will know exactly which wavelength has the min reflection.

 

 

[jiglesi1]

Thank you. I am not new to Ansys but I am new to Optics FDTD so I appreiate your help.

[jiglesi1]

 

I have tried to improve my results by decreasing the thickness of the lnP film using the formula t = lambda/(4n) with lambda = 1.5um and n = 3.21 which gives .1168 um. However in the pics I attached the best result I got was at around -.32 on the y axis for 0.12um for y-span. I was told I am supposed to set my source for 1.5 um but I do not know how to do that since I am aiming for mimimum reflection at 1.5 um. Does anyone know of any other equation I can use or how I may alter my lnP film thickness dimensions to get max transmission at 1.5 um if possible? The source is a y axis injection. Thank you in advance!

 

[Guilin Sun]

For thin film or slab type devices, you can use stackrt to get the theoretical results.

stackrt - Script command

For FDTD simulation, make sure the dispersive material is fit correctly without large RMS errors, and you can use finer mesh for the slab cavity. The result is quite smooth so the simulation time and autoshutoff min are reasonable. Also make sure PML is thick enough to absorb the em waves.