Kosame Saikiran, Josline Mukkath Joseph, Lee Jae-Hyun, Ju Heongkyu
Department of Physics, Gachon University Seongnam-si 13120 Republic of Korea
Department of Materials Science and Engineering, Ajou University Suwon Korea.
Nanoscale Adv. 2024 Apr 23;6(10):2636-2643. doi: 10.1039/d3na01131c. eCollection 2024 May 14.
We report the first observation of spectral blue shift of plasmon resonance of synthesized silver nanoparticles (AgNPs) due to a negative optical nonlinearity of a local ambient medium, , indigo carmine (IC) solution at around 420 nm wavelength. The blue shift occurred at a larger concentration of AgNPs or at a larger concentration of IC solution, being in obvious contrast to spectral red shift which was widely witnessed in plasmon spectral shift in a linear regime. Plasmon-enhanced local fields could excite the third-order optical nonlinearity for blue shift even under continuous (non-pulsed) light illumination. We also found that the plasmon-excited nonlinearity could allow for differential nonlinear response of the IC solution to be even greater than its differential linear response, though appearing to be somewhat inconsistent with what was generally known in light-matter interaction. The demonstrated properties of such anomalous shift of plasmon spectral peaks and its accompanying properties indicated that plasmon technologies could be exploited not only in linear but also in nonlinear aspects for critical optimization in plasmon-energy harvesting systems such as in surface enhanced spectroscopy/microscopy, biomedical imaging/sensing, laser frequency conversion, ultrashort pulse generation, and all-optical switching.
我们报道了首次观察到合成银纳米颗粒（AgNPs）的等离子体共振光谱蓝移，这是由于局部环境介质靛蓝胭脂红（IC）溶液在420 nm波长附近的负光学非线性所致。蓝移发生在较高浓度的AgNPs或较高浓度的IC溶液中，这与在线性区域中广泛观察到的等离子体光谱红移形成明显对比。即使在连续（非脉冲）光照下，等离子体增强的局部场也能激发蓝移的三阶光学非线性。我们还发现，等离子体激发的非线性能够使IC溶液的微分非线性响应甚至大于其微分线性响应，尽管这似乎与光与物质相互作用中的一般认知有些不一致。等离子体光谱峰这种异常移动及其伴随特性所展示的性质表明，等离子体技术不仅可以在线性方面，还可以在非线性方面用于等离子体能量收集系统的关键优化，如表面增强光谱学/显微镜、生物医学成像/传感、激光频率转换、超短脉冲产生和全光开关。
