These include photonic crystals, photonic crystal fibers and metamaterials. Photonic logic gates use nonlinear optical effects. Nanodiamonds offer an alternative to photonic metamaterials for optical computing. However, in disordered photonic nanostructures, the LDOS behave differently. Photonics also includes research on photonic systems. Nanoimprint lithography has been used to fabricate devices for electrical, optical, photonic and biological applications. The Center for Photonics and Electronics works on advanced laser and photonic technology. They are typical micrometer-sized and tunable on the bands of the photonic crystals. See Laser propulsion, Photonic Laser Thruster, Photon rocket. Many of these photonic mechanisms correspond to elaborate structures visible by electron microscopy. This is the basis of the optical band gap in a photonic crystal. The company has a portfolio of analog RF, microwave, millimeterwave and photonic semiconductor products. Such periodic structures are known as photonic crystals. Consider two parties conducting local polarization measurements on a bipartite photonic state. A Bragg grating is an example of this type of photonic crystal.