De Leon Israel, Berini Pierre
Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario, K1N 6N5, Canada.
Opt Express. 2011 Oct 10;19(21):20506-17. doi: 10.1364/OE.19.020506.
A theoretical analysis of noise in high-gain surface plasmon-polariton amplifiers incorporating dipolar gain media is presented. An expression for the noise figure is obtained in terms of the spontaneous emission rate into the amplified surface plasmon-polariton taking into account the different energy decay channels experienced by dipoles in close proximity to the metallic surface. Two amplifier structures are examined: a single-interface between a metal and a gain medium and a thin metal film bounded by identical gain media on both sides. A realistic configuration is considered where the surface plasmon-polariton undergoing amplification has a Gaussian field profile in the plane of the metal and paraxial propagation along the amplifier's length. The noise figure of these plasmonic amplifiers is studied considering three prototypical gain media with different permittivities. It is shown that the noise figure exhibits a strong dependance on the real part of the permittivities of the metal and gain medium, and that its minimum value is 4/π(∼3.53 dB). The origin of this minimum value is discussed. It is also shown that amplifier configurations supporting strongly confined surface plasmon-polaritons suffer from a large noise figure, which follows from an enhanced spontaneous emission rate due to the Purcell effect.
本文对包含偶极增益介质的高增益表面等离激元 - 极化激元放大器中的噪声进行了理论分析。考虑到靠近金属表面的偶极所经历的不同能量衰减通道，根据放大后的表面等离激元 - 极化激元的自发发射率，得出了噪声系数的表达式。研究了两种放大器结构：金属与增益介质之间的单界面结构，以及两侧由相同增益介质界定的薄金属膜结构。考虑了一种实际配置，即正在放大的表面等离激元 - 极化激元在金属平面内具有高斯场分布，并沿放大器长度方向进行傍轴传播。针对三种具有不同介电常数的典型增益介质，研究了这些等离子体放大器的噪声系数。结果表明，噪声系数强烈依赖于金属和增益介质介电常数的实部，其最小值为4/π（约3.53 dB）。讨论了该最小值的来源。还表明，支持强约束表面等离激元 - 极化激元的放大器配置存在较大的噪声系数，这是由于珀塞尔效应导致自发发射率增强所致。
