Electromagnetic wave emission based on optical rectification at terahertz (THz) wavelengths was observed from surface-immobilized gold nanospheres (SIGNs) above a gold surface. Although the excitation wavelength is off-resonant with the localized surface plasmons, the THz emission field was observed to be approximately 4.8 times greater than that from a percolated gold thin film of 10 nm thickness. A theoretical calculation predicts that the light electric field is enhanced in the SIGN system, even at off-resonance wavelengths. The observed THz field amplitude was quadratic with the illumination light field, suggesting that the THz generation is due to a second-order nonlinear optical process.
© 2012 Optical Society of America
Original Manuscript: July 20, 2012
Revised Manuscript: August 15, 2012
Manuscript Accepted: August 19, 2012
Published: September 24, 2012
Kotaro Kajikawa, Yusuke Nagai, Yuichi Uchiho, Gopakumar Ramakrishnan, Nishant Kumar, Gopika K. P. Ramanandan, and Paul C. M. Planken, "Terahertz emission from surface-immobilized gold nanospheres," Opt. Lett. 37, 4053-4055 (2012)