Tip-enhanced second harmonic generation (IMAGE) National Institutes of Natural Sciences Caption (a) Schematic representation of the experiment. Local SHG signal is enhanced by irradiating an infrared laser pulse into the plasmonic nanogap between the gold tip and the gold substrate. (b) SHG spectra obtained with (red) and without (orange) plasmonic nanogap, indicating that the SHG signal is enhanced only when the tip is brought closer due to the plasmonic enhancement effect unique to the tip-substrate nanocavity. Credit Toshiki Sugimoto Usage Restrictions for use in stories about this research License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.