**6. SPR fabrication**

This section and all the fabrication and results have been achieved previously by MQW Group at UCF [56–59, 64]. In this work, a sensor head of optical surface plasmon resonance (SPR) has illustrated in this work. It depends on an inverted-rib dielectric waveguide. The changes happen at the gold metaldielectric interface, in which the resonance wavelength of the surface plasmon is excited. These changes are in relationship with the environment changes that occur at the top metal surface. The sensor head of the SPR with the inverted-rib dielectric waveguide composed of SU-8 polymer layer with 1.5 refractive index, whereas the cladding lower layer contains silicon oxynitride (SiOxNy) with 1.526 refractive index. The top layer is painted with a 50 nm gold thick layer. The design of sensor head of the SPR permits controlling the media of analyte with 1.44 to 1.502 refractive index. By using reference liquids collection that represent the analyte medium, an analyzer of optical spectrum and a broadband light source were utilized to measure the SPR sensor sensitivity. It was realized that when a liquid contacts the gold metal with 1.442 refractive index, the transmission spectrum has a sharp resonance dip at 1525 nm and with using a liquid of 1.502, its position was shifted to 1537 nm. Therefore, based on these measurements, the sensor devices sensitivity was specified to be S = 232 nm.RIU-1. In this section, we demonstrate that the device can be integrated completely with a photodetection unit, a wavelength tunable light source and a liquid delivery system through microfluidic channels to make it an extremely compact unit [56–59, 64].

### **7. SPR simulations and design**

Surface Plasmon is the Propagation of transverse magnetic (TM) surface electromagnetic waves at the dielectric interface of a gold metal. Below is the dispersion relation Eq. (1) which can be used to calculate the propagation constant.

$$k\left(\phi\right) = \frac{\phi}{c} \sqrt{\frac{\epsilon\_M \epsilon\_D}{\epsilon\_{M\*}\epsilon\_D}}\tag{1}$$

The design of the reversed rib waveguide was to solely support the essential TM directed mode. The waveguide's dimensions were chosen depending on waveguide dispersion relationship in Eq. (2).

$$t\_{\vec{k}} = \frac{\text{atan}\left(\sqrt{\frac{n\_{\vec{x}^{\prime}} - n\_{\vec{x}^{\prime}}}{n\_{\vec{x}^{\prime}} - n\_{\vec{x}^{\prime}}}\right) + \pi}}{\sqrt[k]{n\_{\vec{x}^{\prime}} - n\_{\vec{x}^{\prime}}}} k\_0 = \frac{2\pi}{\lambda} \text{ is the free-space propagation constant} \tag{2}$$

Moreover, a particular surface plasmon resonance wavelength will appear from the refractive index of the analyte material that interacts with the gold-metal. To determine theoretical dependence, matching condition criterion for the surface plasmon propagation constant (Eq. (3)) can be used.

$$\beta = \beta' + i\beta'' \approx \frac{\alpha}{c} \sqrt{\frac{\dot{\varepsilon'\_m} \mathcal{E}\_d}{\varepsilon'\_m + \varepsilon\_d}} + i \frac{\varepsilon'''\_m}{2\left(\varepsilon'\_m\right)^2} \frac{\alpha}{c} \left(\frac{\varepsilon'\_m \mathcal{E}\_d}{\varepsilon'\_m + \varepsilon\_d}\right)^{\frac{1}{2}} \tag{3}$$

#### where : , : . ε ε*m d Dieletric constant of metal Dieletric contant of cover material*

After all the equation have been calculated, The SPR sensor with the propagation of the waveguide has been design and simulation as shown in **Figure 9**.

In order to define the wave vectors of the directed mode, the exact values of the refractive indices of the directing and cladding layers are important and therefore satisfy the matching condition for the SP mode to be launched. Hence, to design the top of the SPR sensor, the refractive indices for both films need to be classified carefully. To make the directing layer of the top of the SPR sensor; a SU-8 polymer with a fixed refractive index of 1.568 at 1550 nm, is used. Although the silicon oxynitride (SiOxNy) cladding layer film, generated using plasma enhanced chemical vapor deposition (PECVD), has a refractive index as shown in **Figure 10**, it can be changed by adjusting the relative nitrogen to oxygen composition of the SiOxNy film [56–59, 64].

Eq. (3) calculated the theoretical dependence as appears in **Table 2**.

The beam propagation in the SPR sensor head is shown in **Figure 11** as simulated using a RSoft beam package. It is noted here that the maximum size of the waveguide that can only support the basic TM mode are 4 μm and 500 nm respectively. The input light was given by the enhanced spontaneous emission of an erbium doped fiber transformer.

To guarantee that only the TM mode is launched to the SPR sensor waveguide by A 40× microscope objective lens, a polarizer was used. In **Figure 12**, the transmitted light at the output of the device was focused into an optical fiber. To monitor the transmission spectrum the optical fiber is connected to the Optical Spectrum Analyzer (OSA).

**27**

**Figure 11.**

*Optoelectronics and Optical Bio-Sensors DOI: http://dx.doi.org/10.5772/intechopen.96183*

*Optical waveguide based surface plasmon excitation configuration and schematic of the SPR sensor head.*

*Refractive index (n) and K=kelvin of SU-8 film as function of wavelength measures using ellipsometer.*

1.44 1.463 1539.5 1.47 1.484 1533.8 1.49 1.504 1530 1.5 1.515 1528.1 1.518 1.533 1524.68 1.51 1.5255 1526.2

*(a) Simulation of SPR sensor head performed by RSoft. (b) Fundamental mode for the simulation parameter* 

**Surface plasmon refractive index**

**Theoretical wavelength (nm)**

**Figure 9.**

**Figure 10.**

**index**

**Table 2.**

**Analyte medium refractive** 

*Calculated wavelength vs. the surface plasmon refractive index.*

*from (a). (c) Real fundamental mode after fabrication and testing.*

### *Optoelectronics and Optical Bio-Sensors DOI: http://dx.doi.org/10.5772/intechopen.96183*

#### **Figure 9.**

*Optoelectronics*

**7. SPR simulations and design**

dispersion relationship in Eq. (2).

*n n n n t k n n*

2 2 2

2 2 <sup>0</sup> <sup>0</sup>

ββ

*<sup>g</sup> <sup>k</sup> g s*

atan

ε

film [56–59, 64].

Analyzer (OSA).

doped fiber transformer.

*w s c g s*

π

<sup>−</sup> <sup>+</sup> <sup>−</sup> <sup>=</sup> <sup>=</sup> <sup>−</sup> <sup>−</sup>

plasmon propagation constant (Eq. (3)) can be used.

 β

′ ′

Surface Plasmon is the Propagation of transverse magnetic (TM) surface electromagnetic waves at the dielectric interface of a gold metal. Below is the dispersion

( ) *M D*

<sup>=</sup>

The design of the reversed rib waveguide was to solely support the essential TM directed mode. The waveguide's dimensions were chosen depending on waveguide

Moreover, a particular surface plasmon resonance wavelength will appear from the refractive index of the analyte material that interacts with the gold-metal. To determine theoretical dependence, matching condition criterion for the surface

*c c*

=+ ≈ + <sup>+</sup> ′ ′ + ′

where : , : .

In order to define the wave vectors of the directed mode, the exact values of the refractive indices of the directing and cladding layers are important and therefore satisfy the matching condition for the SP mode to be launched. Hence, to design the top of the SPR sensor, the refractive indices for both films need to be classified carefully. To make the directing layer of the top of the SPR sensor; a SU-8 polymer with a fixed refractive index of 1.568 at 1550 nm, is used. Although the silicon oxynitride (SiOxNy) cladding layer film, generated using plasma enhanced chemical vapor deposition (PECVD), has a refractive index as shown in **Figure 10**, it can be changed by adjusting the relative nitrogen to oxygen composition of the SiOxNy

The beam propagation in the SPR sensor head is shown in **Figure 11** as simulated

To guarantee that only the TM mode is launched to the SPR sensor waveguide by A 40× microscope objective lens, a polarizer was used. In **Figure 12**, the transmitted light at the output of the device was focused into an optical fiber. To monitor the transmission spectrum the optical fiber is connected to the Optical Spectrum

 ε *m d Dieletric constant of metal Dieletric contant of cover material* After all the equation have been calculated, The SPR sensor with the propagation

( ) *m d m m d m d m m d*

ε

 ε

2

 ω

2 . .

 ε ε

′′ ′

ε

 ε 3 2

(3)

*c* ω

*M D*

(1)

<sup>2</sup> is the free space propagation constant (2)

+

relation Eq. (1) which can be used to calculate the propagation constant.

ω

π

λ

*i i*

ε ε

of the waveguide has been design and simulation as shown in **Figure 9**.

Eq. (3) calculated the theoretical dependence as appears in **Table 2**.

using a RSoft beam package. It is noted here that the maximum size of the waveguide that can only support the basic TM mode are 4 μm and 500 nm respectively. The input light was given by the enhanced spontaneous emission of an erbium

εε

′ ′

ω

*k*

**26**

*Optical waveguide based surface plasmon excitation configuration and schematic of the SPR sensor head.*

#### **Figure 10.**

*Refractive index (n) and K=kelvin of SU-8 film as function of wavelength measures using ellipsometer.*


#### **Table 2.**

*Calculated wavelength vs. the surface plasmon refractive index.*

#### **Figure 11.**

*(a) Simulation of SPR sensor head performed by RSoft. (b) Fundamental mode for the simulation parameter from (a). (c) Real fundamental mode after fabrication and testing.*

**Figure 13.** *Emissions spectrum after placing the different sample liquids.*

It is probable that a resonant transfer of power from the waveguide can occur at the specific wavelength. The waveguide mode and the surface plasmon mode match the perfect pairing condition between them. In order for that to happen a wide spectrum of light needs to be launched into the system. For that reason, the spectrum of the transmitted light is almost the spectrum of the input light dip at the wavelength of SPR.

One after another, a set of analyte media with calibrated refractive indices (sample liquids) above the Top of the SPR sensor were implemented. To measure

**29**

**Author details**

Sundos Alabdulkarim3

Thamer Tabbakh1,3, Noha Alotaibi2,3\*, Zahrah A. Almusaylim3

1 Materials Science Research Institute, King Abdulaziz City for Science and

the transmission spectrum OSA was used to decide the wavelength of SPR. The transmission spectra for analyte media of refractive indices 1.462, 1.496, and 1.502 correspondingly. As shown in **Figure 13**, the sharp dip in the transmission spectrum moved to a shorter wavelength while lowering the sample liquid refractive

OB detection technology offers a timely, effective and inexpensive tool to measure analytes in samples. It facilitates the detection in different areas, such as; biomedical, environmental and foods. The development and demand of using such technology will continue to grow within the current and upcoming decades, which will result in introducing new generations of OBs to the analytical and diagnostic

2 Biology and Environment Research Institute, King Abdulaziz City for Science and

4 School of Computer Science and Engineering (SCE), Taylor's University, Malaysia

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

3 General Administration For R&D Labs, King Abdulaziz City for Science and

5 National Center for Desalination and Water Treatment Technology, King Abdulaziz City for Science and Technology (KACST), Riyadh, Saudi Arabia

, N.Z. Jhanjhi4

Technology, Riyadh, Kingdom of Saudi Arabia

Technology, Riyadh, Kingdom of Saudi Arabia

Technology, Riyadh, Kingdom of Saudi Arabia

provided the original work is properly cited.

\*Address all correspondence to: naalotaibi@kacst.edu.sa

,

and Nawaf Bin Darwish<sup>5</sup>

*Optoelectronics and Optical Bio-Sensors DOI: http://dx.doi.org/10.5772/intechopen.96183*

index [54, 56–59].

**8. Conclusion**

markets worldwide.

### *Optoelectronics and Optical Bio-Sensors DOI: http://dx.doi.org/10.5772/intechopen.96183*

the transmission spectrum OSA was used to decide the wavelength of SPR. The transmission spectra for analyte media of refractive indices 1.462, 1.496, and 1.502 correspondingly. As shown in **Figure 13**, the sharp dip in the transmission spectrum moved to a shorter wavelength while lowering the sample liquid refractive index [54, 56–59].
