Menu

Discussion Forum

New Discussion
Filter

Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

Varying the order of diffraction in Plasmonic Wire Grating

Posted Apr 11, 2013, 3:56 p.m. EDT Version 4.2 2 Replies

Snehanshu MAiti
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Hi,
I am simulating in Comsol 4.2.I started simulating the PLASMONIC WIRE GRATING given in the model library.the simulation there is done by varying the angle of incidence.(in the parametric sweep angle of incidence is varied).

I want to modify this a little bit.So instead of angle of incidence i want to vary m(the diffraction order)

i have made the necessary changes .

In global variables i have taken the transmission angle beta_m=asin((m*lam0)/(d*nb)) which comes from m*lam0=d(nb*sin(beta_m)-na*sin(alpha)) here alpha=0 for normal incidence
na=R.I of air(upper domain of simulation)
nb=R.I of glass(lower domain of simulation)

The propagation vectors which i have defined are :

ka=emw.k0
kb=nb*emw.k0
kbmx=kb*sin(beta_m)
kbmy=kb*cos(beta_m)

The geometries and material properties have been defined as usual

In port1 i have taken the upper boundary ,wave excitation on and Eo=exp(-i*ka*x) and beta=abs(ka)

In port2 i have taken the lower boundary ,the Eo=-cos(beta_m)*exp(-i*kbmx*x)
and Eo= sin(beta_m)*exp(-i*kbmx*x) and beta=abs(kbmy)

Then i have added the periodic boundary condition as Floquet condition

In the parametric sweep i have varied m(-2,0.1,2)

But this gives me erroneous results!!
probably i am unable to vary /parametric sweep m.

Kindly help I want to find the transmiision for various m
2 Replies Last Post Apr 14, 2013, 1:40 a.m. EDT
Alexander Kuznetsov
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Apr 12, 2013, 12:43 p.m. EDT
"Varying the order of diffraction" is meaningless in terms of FEM. You launch a wave on a grating, and whatever orders exist, they we be modeled. In the near-field, you can't separate diffraction orders. Moreover, non-propogating (evanescent) modes will also contribute to the field patterns.
"Varying the order of diffraction" is meaningless in terms of FEM. You launch a wave on a grating, and whatever orders exist, they we be modeled. In the near-field, you can't separate diffraction orders. Moreover, non-propogating (evanescent) modes will also contribute to the field patterns.
Snehanshu MAiti
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Apr 14, 2013, 1:40 a.m. EDT
In the model library where they have simulated the Plasmonic wire grating they are showing the 1D plot.(Transmission vs angle of incidence for varying orders).In definition of variables they have calculated the propagation vectors for different orders if u see the details of the model.So they get a 1D plot for transmittivity for different orders .But in subwavelenth grating the diffracted light might always not be confined in the integral orders.They may be present in the non integral orders also if u carefully analyse the grating eqn.So i tried to vary different orders.

If this makes sense can the modes be separated in the far field.I guess the 1D plot in the model have been done for far field

Ultimately i want to plot the transmittivity at the far field in polar coordinates.(i mean the transmitted light as a func of angular variation of the space coordinates at far field)for the normal angle of incidence.What exactly needs to be done.Kindly tell the details

Thanking you

Snehanshu
In the model library where they have simulated the Plasmonic wire grating they are showing the 1D plot.(Transmission vs angle of incidence for varying orders).In definition of variables they have calculated the propagation vectors for different orders if u see the details of the model.So they get a 1D plot for transmittivity for different orders .But in subwavelenth grating the diffracted light might always not be confined in the integral orders.They may be present in the non integral orders also if u carefully analyse the grating eqn.So i tried to vary different orders. If this makes sense can the modes be separated in the far field.I guess the 1D plot in the model have been done for far field Ultimately i want to plot the transmittivity at the far field in polar coordinates.(i mean the transmitted light as a func of angular variation of the space coordinates at far field)for the normal angle of incidence.What exactly needs to be done.Kindly tell the details Thanking you Snehanshu

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.

Suggested Content