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This example provides example simulations which use the grating order transmission analysis group to calculate the fraction of power transmitted into each grating order.  It also shows how to calculate the number of grating orders that exist as a function of wavelength. The grating order transmission analysis group is available from the object library.

 

Solvers

FDTD

Associated files

grating_order_transmission.fsp

grating_order_transmission.lsf

See also

BFAST

Grating examples

Grating projection toolbox

Grating and far field projection analysis objects

grating, find, pinch script commands

grating_order_transmission_screenshot_zoom88

Simulation setup

Calculating the total transmitted power through a monitor is very easy to do with the transmission function.  However, it is sometimes necessary to calculate the power scattered into a particular grating order of a periodic structure.  This calculation is more challenging, requiring both the grating and transmission functions, plus a reasonable amount of matrix manipulation.  The analysis object also calculates the number of supported grating orders.

 

The associated simulation files use the grating order transmission analysis object to do these calculations. You can insert this object from the object library in the far field projections section.  

 

Results

To reproduce these results, open grating_order_transmission.fsp, then run grating_order_transmission.lsf. The script will run the simulation, then run the analysis object scripts and create some final plots, as shown below. Note that we used BFAST  source so all the interested wavelengths have the same incident angle.

 

Figures created by the analysis objects:


Transmission monitor

Reflection monitor

Number of supported grating orders

 

Notice that the -Z direction (reflection) supports more orders. This is due to the higher index of the substrate. Also notice that more grating orders are supported at shorter wavelengths.

grating_order_t_num_zoom51

grating_order_r_num_zoom51

Total transmission through the monitor, and the transmission to the (0,0) grating order.  

 

Notice that when there is only one supported grating order, T_(total) is equal to T_(0,0)

grating_order_t_zoom51

grating_order_r_zoom51

Propagation direction of the (0,0) grating order, in terms of theta, phi.

 

grating_order_t_direction_zoom51

grating_order_r_direction_zoom51

The propagation direction and strength of the grating orders at 0.8um.

grating_order_t_0p8um_zoom70

grating_order_r_0p8um_zoom70

 

Figures created by the script grating_order_transmission.lsf.

Number of supported grating orders in both reflection and transmission.

grating_order_rt_num_zoom51

 

Total reflection and transmission, and the reflection and transmission into the (0,0) grating order.

grating_order_rt_zoom51

 

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