The photonics and ARCoating testbeds in Nevergrad

We detail the testbeds which can be found in the photonics and ARCoating test cases in Nevergrad. These testbeds, beyond their practical importance, are especially modular-and like all problems in photonics, possess a very high number of local minima. They constitute simple but crucial design challenges: designing a multilayered structure which can reflect light at a given frequency, reflect light on a whole range of frequencies or cancel the reflectivity ; designing a complex structure able to diffract the blue part of the spectrum and to cancel the reflectivity at any other wavelength.