**4. Scattering cross section of noble metal nanosphere: FDTD technique**

We have plotted the scattering cross section of silver nanosphere of radius 50 nm surrounded by silica matrix as shown in **Figure 4**. In the previous study, we have chosen the smaller-sized nanoparticle whose optical properties have been studied in quasi-static domain. In quasi-static domain, we have chosen the static behavior of charge instead of oscillating behavior because the particle size is much smaller than the wavelength of light. When the particle size is smaller than the wavelength of light, in such a case, the particle feels the oscillating field because the electric field is no more static throughout the particle volume. Therefore, we have used the FDTD technique to study the plasmonic signature of larger-sized silver metal nanosphere. This shows the surface plasmon resonance at wavelength 564nm, as shown in **Figure 4**a. We have also plotted the near-field distribution of 50 nm silver nanosphere at its SPR wavelength as shown in **Figure 4**b. The computed electric field gives the normalized field intensity magnitude 70 unit.

under the SPR, maximum sun light can be harvested to produce electricity. The electric field distribution near the metal surface has also been done at SPR wavelength 625 nm as shown in **Figure 5**b. The magnitude of normalized field is indicated in scale bar. In nutshell, optical properties of two different types of metal such as silver and gold are studied in silica environment.

**Figure 5.** (a) Wavelength-dependent extinction spectra. (b) Electric field distribution of gold metal nanoparticle of radius

**Figure 4.** (a) Wavelength-dependent extinction spectra and (b) electric field distribution silver metal nanoparticle of

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Here, we have analyzed the optical properties of noble metal nanoparticle in different regime electromagnetic spectra. The special emphasis has been given on the semi-analytical as well as numerical model. Two different types of numerical techniques such as FDTD and COMSOL Multiphysics are used to study the plasmonic resonances which cover a broader range of

**5. Conclusions**

50 nm embedded in silica matrix.

radius 50 nm embedded in silica matrix.

Further, we have also studied the optical properties of larger-sized gold nanoparticle embedded in silica matrix as shown in **Figure 5**. The scattering cross section of 50 nm gold nanosphere has been plotted using FDTD technique. Here, we have solved Maxwell's equation to obtain the cross-sectional profile, which has the dimension of area. The scattering is the reradiation of electromagnetic field which is absorbed by the surrounding media. The higher the scattering from the nanoparticle, the higher the photon absorption into the active medium. For 50 nm gold nanosphere, SPR wavelength was observed at 625 nm (**Figure 5**a), and we believe that

Plasmonic Resonances and Their Application to Thin-Film Solar Cell http://dx.doi.org/10.5772/intechopen.75015 159

**Figure 4.** (a) Wavelength-dependent extinction spectra and (b) electric field distribution silver metal nanoparticle of radius 50 nm embedded in silica matrix.

**Figure 5.** (a) Wavelength-dependent extinction spectra. (b) Electric field distribution of gold metal nanoparticle of radius 50 nm embedded in silica matrix.

under the SPR, maximum sun light can be harvested to produce electricity. The electric field distribution near the metal surface has also been done at SPR wavelength 625 nm as shown in **Figure 5**b. The magnitude of normalized field is indicated in scale bar. In nutshell, optical properties of two different types of metal such as silver and gold are studied in silica environment.

#### **5. Conclusions**

of spherical-shaped metal nanoparticle [16]. We have used the Lumerical-based finite-difference time-domain technique to study the optical properties of noble metals. The metals are silver and gold whose optical constants are taken from the literature [8, 9]. These metals are surrounded by silica environment having constant dielectric constant. The objective of the work is to analyze the distribution of electric field near the metal surface in a resonance condition.

**Figure 3.** Electric field distribution of (a) silver and (b) gold nanosphere of radius 7 nm surrounded by silica matrix

We have plotted the scattering cross section of silver nanosphere of radius 50 nm surrounded by silica matrix as shown in **Figure 4**. In the previous study, we have chosen the smaller-sized nanoparticle whose optical properties have been studied in quasi-static domain. In quasi-static domain, we have chosen the static behavior of charge instead of oscillating behavior because the particle size is much smaller than the wavelength of light. When the particle size is smaller than the wavelength of light, in such a case, the particle feels the oscillating field because the electric field is no more static throughout the particle volume. Therefore, we have used the FDTD technique to study the plasmonic signature of larger-sized silver metal nanosphere. This shows the surface plasmon resonance at wavelength 564nm, as shown in **Figure 4**a. We have also plotted the near-field distribution of 50 nm silver nanosphere at its SPR wavelength as shown in **Figure 4**b.

**4. Scattering cross section of noble metal nanosphere: FDTD** 

The computed electric field gives the normalized field intensity magnitude 70 unit.

Further, we have also studied the optical properties of larger-sized gold nanoparticle embedded in silica matrix as shown in **Figure 5**. The scattering cross section of 50 nm gold nanosphere has been plotted using FDTD technique. Here, we have solved Maxwell's equation to obtain the cross-sectional profile, which has the dimension of area. The scattering is the reradiation of electromagnetic field which is absorbed by the surrounding media. The higher the scattering from the nanoparticle, the higher the photon absorption into the active medium. For 50 nm gold nanosphere, SPR wavelength was observed at 625 nm (**Figure 5**a), and we believe that

**technique**

having N = 1.54.

158 Emerging Solar Energy Materials

Here, we have analyzed the optical properties of noble metal nanoparticle in different regime electromagnetic spectra. The special emphasis has been given on the semi-analytical as well as numerical model. Two different types of numerical techniques such as FDTD and COMSOL Multiphysics are used to study the plasmonic resonances which cover a broader range of applications. The computed electric field magnitude at SPR wavelengths corresponding to smaller- and larger-sized metal nanoparticle would clearly suggest experimentalist to fabricate various sizes of nanoparticle whose SPRs are preknown.

[5] Bellido EP, Zhang Y, Manjavacas A, Nordlander P, Botton GA. Plasmonic coupling of multipolar edge modes and the formation of gap modes. ACS Photonics. 2017;**4**:1558-

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