RP Photonics logo
RP Photonics
Modeling & Design Software
Technical consulting services on lasers, nonlinear optics, fiber optics etc.
Profit from the knowledge and experience of a top expert!
Powerful simulation and design software.
Make computer models in order to get a comprehensive understanding of your devices!
Success comes from understanding – be it in science or in industrial development.
The famous Encyclopedia of Laser Physics and Technology – available online for free!
The ideal place for finding suppliers for many photonics products.
Advertisers: Make sure to have your products displayed here!
powerful tools for efficient laser development and laser science
This page gives you an overview on our software products.
RP Fiber Calculator is a convenient tool for calculations on optical fibers.
RP Fiber Power is an extremely flexible tool for designing and optimizing fiber devices.
RP Resonator is a particularly flexible tool for laser resonator design.
RP ProPulse can simulate the pulse evolution e.g. in mode-locked lasers and sync-pumped OPOs.
RP Coating is a particularly flexible design tool for dielectric multilayer systems.
RP Q-switch can simulate the power evolution in Q-switched lasers.
Most of our software products support a powerful script language, which gives you an extraordinary degree of flexibility.
Here you learn about software license conditions, updates and upgrades, etc.
Competent technical support is a key quality associated with software from RP Photonics.
RP Photonics has distributors in various countries.
The RP Photonics Software News keep you updated on our developments and give the users additional interesting hints.
Here you can make inquiries e.g. concerning technical details, prices and quotations.
en | de

RP Coating – Advanced Software for
Designing Optical Multilayer Structures

Demo File: Dichroic Mirror

Here, we design a dichroic mirror with high reflectivity at 1064 nm and high transmission at 808 nm at normal incidence. Such mirrors are often used for pumping Nd:YAG and Nd:YVO4 lasers.

As an initial design, we use a simple Bragg mirror:

beam from superstrate
substrate: BK7
for j := 1 to 8 do
begin
* TiO2, l / 4 at 1200
* SiO2, l / 4 at 1200
end
superstrate: air

Such a mirror already has a high reflectivity at 1064 nm. The transmission at 808 nm, however, is not ideal, even though that wavelength is outside the main reflection band.

Then we define the figure-of-merit function describing the design goal:

d_units: nm
l_units: nm
 
l_HR := 1064  { HR wavelength }
l_HT := 808   { HT wavelength }
 
FOM() := 
  sqrt(sum(d := -20 to +20 step 5, T(l_HR + d)^2)
      +sum(d := -20 to +20 step 5, R(l_HT + d)^2))

With that, we “punish” any transmission around 1064 nm and any reflectivity around 532 nm. It is advantageous to demand such properties not only at isolated wavelengths, as that may lead to designs which are sensitive to fabrication errors.

We can then apply a simple local optimization:

optimize coating for minimum of FOM(), ytol = 1e-5

Next, we make a diagram showing the reflectivity profile:

diagram 1:
 
"Reflectivity Profile"
["Merit value: ", FOM():d3]
 
x: 400, 1600
"wavelength (nm)", @x
y: 0, 100
"reflectivity (%)", @y
frame
hx
hy
 
f: 100 * R(x), color = red, width = 3

When executing the script, we get the following:

reflectivity profile of a dichroic mirror

A second diagram is made for showing the obtained thin-film design:

diagram 2:
 
"Design of the Multilayer Structure"
 
x: -500, get_d(0) + 500
"position (nm)", @x
y: 0, 3
"refractive index (nm)", @y
frame
 
! begin
    for j := 1 to nolayers() do
    begin
      var g;
      g := if get_material$(j) = "TiO2" then 0.8 else 0.9;
      setcolor(rgb(g,g,g));
      box(get_z(j), get_z(j + 1) + i * CS_y2);
    end;
    draw_cs();  { draw the coordinate system again }
  end
 
[get_d(j):f0:"nm"],
 (get_z(j) + 0.5 * get_d(j))c, (0.1 * CS_y2)b, direction = 90,
 for j := 1 to nolayers()
"substrate", (-200)c, (0.1 * CS_y2)b, direction = 90
"superstrate", (get_d(0) + 200)c, (0.1 * CS_y2)b, direction = 90
 
f: n(x, 1200), step = 1, color = blue
design of dichroic mirror

We see that this design does not deviate much from that of a simple Bragg mirror.

arrow