Surface-enhanced second-harmonic diffraction: Experimental investigation of selective enhancement

Abstract

Recent theoretical predictions demonstrating large enhancements of second-harmonic diffraction through the control of surface harmonic composition when the surface-plasmon polariton ͑SPP͒ is excited on a corrugated silver surface have been investigated experimentally for the specular order. Interpretation of the mechanism of enhancement in terms of a three-step selective scattering process involving only two spatial harmonics has been found to be justified. Fourier blaze holography, which permits the phase-and amplitude-controlled superposition of multiple harmonics in photoresist, has been used to fabricate the nanostructured, biperiodic gratings. Surfaces have been characterized by atomic force microscopy and Heitmann's method. As predicted, surfaces with optimized spatial frequency composition equal or exceed randomly rough surfaces in the enhancement of second-harmonic reflection relative to a flat silver surface. Enhancement produced by simultaneous excitation of counterpropagating SPP modes at the pump and second-harmonic frequencies has also been detected by varying grating wave vector to tune through a double resonance condition. Factors affecting the quantitative agreement between enhancement measurements and theoretical predictions are briefly discussed.

Kinetic study on the binding of lectin to mannose residues in a polymer brush

“…For example, the absorbance of the colloidal gold is sensitive to the refractive index of the surrounding medium [29]. Therefore, they are quite useful materials in applications to optical devices [30,31], surface-enhanced spectroscopies [32][33][34][35][36][37][38][39][40], and chemical and biological sensors [41][42][43][44].…”

Plasmonic band gap structures for surface-enhanced Raman scattering

“…Previously, biharmonic grating structures have been used to enhance second harmonic generation [25] and to form plasmonic band gap cavities [26]. Biharmonic surface is made up of a grating with two harmonic components.…”

Nonlinear optics on nano/micro-hierarchical structures on metals: focus on symmetric and plasmonic effects

“…Because SHG light intensity is proportional to the incident light intensity squared, the SP-induced electric field enhancement at the surface yields significantly enhanced SHG emission. As representative works, Quail and Simon [21] and Pipino et al [22] have focused on studying SHG enhanced by propagating SPs on metal nanograting. They found that the diffracted SHG was enhanced at a specific incident angle.…”

“…Despite the extensive research on the SP-assisted nonlinear processes in pure metals, hybrid, or composite materials [22,29–33], a systematic study on the effects of micro/nano-hierarchical structures on nonlinear optical processes is currently lacking. As mentioned above, both nanostructures and microstructures are important for generating SPs.…”