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This example shows how to calculate the grating orders from a blaze grating. This grating has many grating orders at each wavelength. In order to capture the signature of the total reflection and transmission, more frequency points in the monitors are required.

 

Solvers

FDTD

 

Associated files

grating_blaze.fsp

grating_blaze.lsf

See also

BFAST

Gratings

Grating order transmission

Grating projection toolbox

Broadband Injection Angles  

 

 

grating_blaze_screenshot

Simulation setup

A blaze grating is shown in the simulation file above.  It is composed of a low index (1.4) substrate with a 40nm thick  high index (3.4) coating.  The grating angle is 30 degrees.  A broadband plane wave source is incident at 15 degrees.  We will use the grating order transmission analysis objects described in the Grating order transmission section to measure the reflection and transmission.  

 

Results

Open grating_blaze.fsp and run the simulation.  When it finishes, use the script grating_blaze.lsf to calculate the reflection and grating orders at a fixed wavelength from the grating.  Note that we used BFAST  source so all the interested wavelengths have the same incident angle.

 

The first figure shows the index profile of the grating.

grating_blaze_index_zoom93

The second figure shows the reflection of all diffraction orders as a function of wavelength from 0.4um to 0.7um. As can be seen from the figure below, at each wavelength, there are many diffraction orders. In order to get a smooth reflection curve, more frequency points than usual is required. In this example, 150 frequency points are used. However, as can be seen, even more frequency points (such as 200) are needed to have smoother result.  

 

grating_blaze_reflection_all_order_zoom60

The third figure shows the reflection as a function of angle for a given wavelength of 0.5um.  If you want to get this result at any other wavelength, just simply modify the "target_wavelength" in the script.

grating_blaze_reflection_zoom60

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