合成在特定波長有表面電漿共振之金屬奈米結構

Abstract

我們利用模擬退火法與邊界積分方程法來合成在特定波長具有表面電漿共振特性的金屬奈米結構。數值結果依應用可分為: 藍光LED (波長435 nm)、白光LED (波長450 nm 與570 nm)、與綠光LED(波長535 nm)。藍光LED 係由二金屬圓柱部分嵌於金屬半空間之奈米結構所組成。吾人首先合成一結構，其表面電漿極化子和局域表面電漿子在單一波長 (435 nm) 能有效耦合。接著再合成另一結構，使其在另一波長 (520 nm) 僅有局域表面電漿子之共振。數值模擬顯示: 表面電漿極化子和局域表面電漿子在單一波長有效耦合時，確實可提升其附近電偶極之輻射量。白光LED 係由二分離之金屬圓柱與一金屬半空間之奈米結構所組成。吾人合成一結構，在藍光波長(450 nm)與黃光波長 (570 nm) 皆具有局域表面電漿子共振，因而提升混光而成的白光發光量。綠光LED 係由二分離之金屬橢圓柱與一金屬半空間之奈米結構所組成。吾人合成一結構，其表面電漿極化子和局域表面電漿子在單一波長 (535 nm) 能有效耦合，因而提升電偶極之輻射量與輻射效率。

The simulated annealing and the boundary integral-equation methods are used to synthesize metallic nanostructures with surface-plasmon resonance properties at designated wavelengths. The numerical results include three parts according to the possible applications: blue-light LEDs (wavelength 435 nm), white-light LEDs (wavelengths 450 nm and 570 nm), and green-light LEDs (wavelength 535 nm). For the blue-light LEDs, the structure consists of two metallic circular cylinders partially embedded in a metallic half-space. We first synthesize a metallic nanostructure such that the surface plasmon polariton (SPP) and the localized surface plasmon (LSP) couple effectively at their common resonant wavelength (435 nm). Next, we synthesize another structure for optimization at wavelength 520 nm, at which only the LSP resonance occurs. From numerical simulations, it is demonstrated that the enhancement of the dipole emission is better for optimization at wavelength 435 nm than that at wavelength 520 nm. In the aspect of white-light LEDs, the structure is composed of two separate metallic circular cylinders and a metallic half-space. We synthesize a metallic nanostructure, which has LSP resonances at wavelength 450 nm (blue light) and at wavelength 570 nm (yellow light), leading to the enhancement of white-light emission. For the green-light LEDs, the structure consists of two separate metallic elliptical cylinders and a metallic half-space. We synthesize a metallic nanostructure such that the SPP and LSP couple effectively at their common resonant wavelength (535 nm), leading to the enhancement of both the dipole emission and the emission efficiency.