[Expectant_Philosopher (OP)]

Can Second Harmonic Generation be the basis for a visible light cloak?  If we created a waveguide to create non-linearity, then use a prism to split the light into a second harmonic wave and a residual wave, then use wave guides to reflect the second harmonic wave back towards the light source and direct the residual wave towards the opposite side. The second harmonic wave automatically shifts visible light beyond the detectable wavelength detectible by human vision.  With human vision in the 390 to 700 NM range, the second harmonic wave would half the wavelength of the reflected light to the range 195 to 350 NM which is out of normal vision parameters.