Plasmooptoelectronic tuning of optical properties and SERS response of ordered silver grating by free carrier generation

Abstract

Electrical current induced reversible tuning of the optical properties of ordered silver gratings was proposed. Polymer surface was patterned by excimer laser leading to creation of grating. Subsequently, thin silver layer was deposited onto the polymer grating. Prepared structure is capable of supporting surface plasmon polariton excitation and propagation. To introduce an electric current in direction along the features of the grating additional contacts (Au, Ag, Si, Ge, and their combination) were vacuum deposited. Application of the electric voltage leads to the shift of the wavelength position of surface plasmon polariton by several nanometers and to a change of its absolute intensity by up to 30% in regard to its initial value. The observed phenomenon depends strongly on the grating amplitude and contact between the silver grating and the supply electrodes. The strong electric triggering was observed in the case of evaporated silver or gold electrodes. Oppositely, when the semiconductor materials (Ge, Si) were used, no optoelectronic response was observed. The observed optical tuning can be attributed to a change of free electron concentration in the silver grating due to impact ionization of the metal atoms. The observed phenomenon was exploited to modify SERS response of a thin polystyrene layer deposited onto silver grating. Electrically triggered increase and decrease of SERS intensity was found to depend on grating structure and excitation wavelength. The studied phenomenon is dynamic, continuous, reversible and voltage-controlled, and has a broad range of potential applications for example in the field of triggerable plasmon structures.