diffraction grating


#1

Hello,
I want to simulate the optical properties of diffraction grating a in this file:Tung fiber 1.fsp (1.2 MB).
My experimental procedure consists of keeping the grating at an angle (0) ( angle of incidence).
I want to simulate the strucutre in order to get the different order of grating (1st and 2nd)…how could I do so?
My source wavelength is a laser source of wavelength 550 nm.


#2

Hi,
I was able to make this plot

It shows the transmission to different orders from -7 to 7. This makes a total of 15 order of diffraction which is the same num_orders calculated by the analysis group.

To make this plot: Run the analysis group. Right click>> visualize>> T_grating
This will plot a lot of Data sets: You are interested in the transmission of different orders which is the first one (T_grating).

To interpret other data sets, check this part of the script:

Input properties

make plots: 1 to make plots, 0 otherwise

n,m target: grating order to plot. Thess parameter only affects the plots. They does not affect the output results.

lambda target: wavelength to plot. Thess parameter only affects the plots. They does not affect the output results.

Output properties

T(f): total transmitted power vs frequency. Will be negative for power flowing in negative direction

T_grating(n,m,f): (3D) fraction of transmitted power to each grating order, S & P polarization components,

direction cosine vectors, and theta,phi angles

T_grating(n,f): (2D) fraction of transmitted power to each grating order, S & P polarization components,

and theta angle

num_orders(f): number of supported grating orders

Notes

- grating_S, grating_P are normalized such that |grating_S|^2 gives the fraction of the source power to each grating order

that is S polarized. |grating_S|^2+|grating_S|^2 = T_grating.

- Interpretation of results for various monitor orientations for 3D simulations:

XY plane: n, U1 correspond to X axis. m, U2 correspond to Y axis

XZ plane: n, U1 correspond to X axis. m, U2 correspond to Z axis

YZ plane: n, U1 correspond to Y axis. m, U2 correspond to Z axis


#3

Thanks…to know also the angle of the order of the grating…say 1st order and the angle is it theta that I should consider?


#4

Hi @tapajyoti_das_gupta,
You can do the same steps:

To make this plot: Run the analysis group. Right click>> visualize>> T_grating

This will plot a lot of Data sets: This time you are interested in the attribute called “Theta”. You will get a plot like this one showing the theta of each diffraction order:

To plot the Transmission vs. the angle:
Copy the following script to script prompt window:

x = T_grating.theta;
T= T_grating.T_grating;
plot(x, T);

You will get this plot

Hope this is helpful… And sorry for the late response. I just saw it. If you have any questions, please mention me. :slight_smile:


#5

Hi @aya_zaki

Thanks again…the transmission plot is wrt to thetat right?
Also …when we do the grating analysis the target wavelength is a single
wavelength. This is not aa problem here since we use a single source.
However if we want a white light source, then could we pu different target
wavelengths?
thanks
Tapajyoti

Tapajyoti DAS GUPTA
Laboratoire de Physique de la Matière Condensée (PMC),
Ecole Polytechnique
Route de Saclay,
91120 Palaiseau, FRANCE


#6

The last plot shown in @aya_zaki’s previous reply shows transmission plotted against theta in degrees along the x-axis.

You are correct that if you have a broadband simulation for white light, you can change the target wavelength in the grating_transmission analysis group. You just need to set the “lambda target” property in the analysis group’s Analysis->Variables tab. Hopefully this helps!