The existence of large nonlinear optical coefficients is one of the preconditions for using nonlinear optical materials in nonlinear optical devices. For a crystal. such large coefficients can be achieved by matching photon energies with resonant energies between different bands. and so the details of the crystal band structure play an important role. https://www.jmannino.com/quick-save-Canon-imageCLASS-MF227dw-Monochrome-Multifunction-Laser-Printer-great-choice/