3D photonic band gap crystals can be used to manipulate light, for example to increase the emission of an emitter. An inverse woodpile photonic band gap crystal has been fabricated in silicon by FIB lithography and reactive ion etching. The resulting photonic crystal was then infiltrated with quantum dots in toluene which emit above the photonic band gap. Quantum dots inside the photonic crystal emit with 24 times more intensity than quantum dots outside the crystal and also exhibit a 7 times increase in emission speed.
Goodwin et al. (Mon,) studied this question.