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Surface-normal second harmonic emission from AlGaAs high-contrast gratings

Second harmonic (SH) generation from AlGaAs near-wavelength high-contrast gratings was studied in polarization-dependent reflection measurements. The grating design is critical in determining the strength and polarization of the second harmonic signal. The second harmonic response was enhanced by more than 3 orders of magnitude compared to flat AlGaAs surfaces without the gratings. These enhancements are due to the diffractive nature of the gratings, specifically their ability to change the direction of light waves.