**5.3 Backscattering optical interferometric**

Backscattering interferometry (BI) sensor is another category of optical biosensors. The detector can measure the uncalculated reflected intensity of a small sensing area by using a single wavelength laser light. Based on the sub wavelength formation on the top sensing area, the detector results in an interference pattern [46].

The improvement of Backscattering as a label-free detection technique appeared in field and applications as following: (a) applied to what is called lab-on-a-disc, (b) Silicon Sensor Surfaces SSS (bio reactions) application (c) Measuring minor refractive index transformations in capillaries of fused silica, and (d) Bio molecular interaction control in microfluidic channels [47].

Backscattering applications started with measuring bio molecular interactions on porous silicon based optical systems. In the pores, the surface is adjusted using elements of bio molecular recognition. Fabry-Perot fringes result in an interference pattern of impinging white light above and below the optical interference layer [48].

#### **Figure 4.**

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**Figure 6.**

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

the detection limit obtained was 0.112 μg.

**5.5 Surface-enhanced Raman scattering**

**5.4 Reflectometric interference spectroscopy (RIfS)**

In order to investigate molecular interaction, a physical technique known as reflectometric interference spectroscopy is used. This technique depends on white light being interfered at thin films as shown in **Figure 6**. In Reflectometric Interference Spectroscopy (RIfS), biomolecular reactions happen on the sensing component. The sensing component is a glass slide adjusted with a thin layer of translucent dielectric material (e.g., SiO2, SiO2–Ta2O5). When the white light strikes the reverse side of the glass, an intervention occurs from the partial beams, reflected at each interface. This intervention alternates maximum and minimum reflectance range [50], which corresponds to the constructive and destructive reflected radiation interference. Biomolecular reactions cause build-up of an adlayer on top of the dielectric, which increases the optical path length. This results in a reflectance spectrum change [51]. This change can be associated with the intensity of the reacting biomolecules and is equivalent to the increase in thickness. Information about the viscosity and refractive index of the adsorbed protein layer is given by alterations in the polarized light phase and amplitude. For the identification and quantification of diclofenac in bovine milk, this approach was used, and

Surface Enhanced Raman scattering (SERS) spectroscopy method are used for the extremely sensitive biological analytes. With rapid growth during the last four decades, surface-enhanced Raman scattering has become one of the most reliable spectroscopic method. Applications for (SERS) detection are expanding quickly in various fields such as materials science, chemistry, biochemistry, and life sciences. Remarkable growth has resulted in biological and biomedical sensing applications from advances in the creation and production of SERS-based biosensors particularly. Electromagnetic improvement leads primarily to SERS improvement, and the configurations of the hotspot are essential to the success of responsive and reproducible detection [52]. Biosensors that are SERS-based can be generated according to the sensing requirements through direct and indirect methods. To define SERS, it is an extremely sensitive optical detection method using lasers in molecules adsorbed on the top of a metal nanoparticle in order to excite vibrational transitions. The Raman cross-section for a molecule on a surface is enhanced by factors of 10 caused by large optical fields. Because of molecular vibrational events, Raman scattering depends mainly on the loss (Stokes) or gain (anti-Stokes) of energy; from inflexible scattered photons and represents the information on the molecular structure, allowing in situ and real-time detection [53, 54]. SERS is a subclass of

*Schematic illustration of (a) the RIfS principle and (b) the RIfS measurement system [49].*

*(a) Extrinsic types of fiber optic sensors, and (b) intrinsic types of fiber optic sensors [43].*

*Optoelectronics*

iarity of end-user [45].

interference pattern [46].

layer [48].

**Figure 4.**

**5.3 Backscattering optical interferometric**

interaction control in microfluidic channels [47].

chemical corrosion, high temperature, high voltage, and pressure. 2) Low power, very small size, and passive. 3) Exceptional performance such as wide bandwidth and high sensitivity. 4) Processing of long range. 5) They applied distributed or multiplexed measurements to cope with their main flaw of high cost and unfamil-

Backscattering interferometry (BI) sensor is another category of optical biosensors. The detector can measure the uncalculated reflected intensity of a small sensing area by using a single wavelength laser light. Based on the sub wavelength formation on the top sensing area, the detector results in an

The improvement of Backscattering as a label-free detection technique appeared in field and applications as following: (a) applied to what is called lab-on-a-disc, (b) Silicon Sensor Surfaces SSS (bio reactions) application (c) Measuring minor refractive index transformations in capillaries of fused silica, and (d) Bio molecular

Backscattering applications started with measuring bio molecular interactions on porous silicon based optical systems. In the pores, the surface is adjusted using elements of bio molecular recognition. Fabry-Perot fringes result in an interference pattern of impinging white light above and below the optical interference

*Evanescent wave fluorescence biosensors working method and the separation of molecules in the surface.*

*(a) Extrinsic types of fiber optic sensors, and (b) intrinsic types of fiber optic sensors [43].*

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**Figure 5.**
