RP Coating – Advanced Software for
Designing Optical Multilayer Structures

This demo file provides a custom form with which one can easily design optical filters which have a high transmission at short wavelengths and high reflectivity at long wavelengths (short pass) or vice versa (long pass). The design is essentially that of a Bragg mirror, but with added λ/8 layers at the top and the bottom. If required, the performance can be further improved with an optional local numerical optimization.

It is instructive to see the used script code for the definition of the coating, based on various variables which are entered in the form:

beam from superstrate
substrate: (material_s$)
if DesignType$ = "Bragg" then
begin
  for j := 1 to N_Bragg do
  begin
    * (material_l$), l/4 at l_Bragg
    * (material_h$), l/4 at l_Bragg
  end
end
else if DesignType$ = "short-pass" then
begin
  * (material_l$), l/8 at l_Bragg
  for j := 1 to N_Bragg do
  begin
    * (material_h$), l/4 at l_Bragg
    * (material_l$), l/4 at l_Bragg
  end
  * (material_h$), l/4 at l_Bragg
  * (material_l$), l/8 at l_Bragg
end
else if DesignType$ = "long-pass" then
begin
  * (material_h$), l/8 at l_Bragg
  for j := 1 to N_Bragg do
  begin
    * (material_l$), l/4 at l_Bragg
    * (material_h$), l/4 at l_Bragg
  end
  * (material_l$), l/4 at l_Bragg
  * (material_h$), l/8 at l_Bragg
end
superstrate: air

The first diagram shows the reflectivity profile of a short-pass filter, designed for transmitting pump light at 808 nm into a laser operating at 1064 nm:

A second diagram shows the reflectivity as a function of wavelength and angle of incidence:

As we are using a custom form, both the form and the underlying calculations can be modified by the user according to specific requirements.