**4. Conclusion**

*Cext* <sup>=</sup> \_\_\_\_ <sup>4</sup>*<sup>k</sup>*

*Cabs* <sup>=</sup> \_\_\_\_ <sup>4</sup>*<sup>k</sup>*

absorption and scattering, *Qi*

16 Plasmonics

where *Ci*

radius of target.


{Im [*p* → *i* .(*α<sup>i</sup>* −1 )<sup>∗</sup> *p* → *i* ∗ ] <sup>−</sup> \_\_2 <sup>3</sup> *k*<sup>3</sup> |*p* → *i* | 2

*Csca* = *Cext* − *Cabs Qi* <sup>=</sup> *<sup>C</sup>*\_\_\_\_*<sup>i</sup>*

*πaeff* 2

The simulation effects could be visualized in terms of scattering cross section as shown in **Figure 4**. A 50 nm radius gold metal sphere is discretized into 4224 number of dipole to see the plasmonic properties like scattering cross section and surface plasmon resonance. The SRP

wavelength of 50 nm gold nanosphere was observed at wavelength 560 nm.

**Figure 4.** Wavelength dependent scattering cross section of 50 nm gold nanosphere surrounded by air.

signifies the optical cross section, *i* represents the running index includes extinction,

represents the normalized optical cross section and *aeff*


Im{*E* → *i*,*inc* ∗ .*p* →

*<sup>i</sup>*} (13)

} (14)

(15)

effective

The work described the optical properties of plasmonic nanogeometries in terms of optical cross section and surface plasmon resonance. Two different types of metals like silver and gold are taken into account to see the optical properties. The surface plasmon resonance corresponding to these metals lies in visible range of electromagnetic spectrum wherein most of the applications exist. Therefore, the work guides to plamonic community to simulate various types of metal nanostructure which exhibit SPR in different part of electromagnetic spectrum. These tunable nature of surface plasmon resonances can be used in many purposes such as sensing, photovoltaic and Raman spectroscopy.
