Figure 4.

Nonlinear crystals can double the frequency of an incident laser beam, conserving the energy in the optical fields. In addition to the conservation of energy, the conservation of momentum leads to a doubling of the OAM per photon.

Nonlinear crystals can double the frequency of an incident laser beam, conserving the energy in the optical fields. In addition to the conservation of energy, the conservation of momentum leads to a doubling of the OAM per photon.