## 3 Results and Discussion
### Sensor MgF\({}_{2}\)-Al  
The operational angle is 61\({}^{\circ}\) because it is where there is more distance among the reflectance curves and each concentration is better distinguished. The thickness of the MgF\({}_{2}\) is 110 nm and the aluminum is 10 nm. We have chosen the compound MgF\({}_{2}\) and  
Figure 4: Reflectance curve vs. concentration of sucrose. Figure 3: Reflectance curve vs. refractive index of the sucrose solution. the elements Ag because they had refractive indices that made the curves in Figure 5 more widely spaced, in this way, they could better distinguish between concentrations by increasing the sensitivity with respect to the other substances. Figure 5 shows the reflectance curves. In this configuration, the range of refractive indexes is less than the sensor with the silver layer. The reflectance curve vs. refractive index of the concentration of sucrose is shown in Figure 6.  
Figure 5: Reflectance curves as a function of the angle of incidence of the light in the prism for the range of refractive index values. Figure 6: Reflectance curve vs. refractive index of the sucrose solution. The increase in reflectance with the refractive index is a monotonically increasing function as in the sensor with aluminum although this one is a little more linear than the previous one. In the aluminum sensor, the sensitivity values are between 2.5 RIU\({}^{-1}\) and 5.7 RIU\({}^{-1}\), and the resolution is between 3.5 \(\times\) 10\({}^{-4}\) RIU and 7.9 \(\times\) 10\({}^{-4}\) RIU. This sensitivity decreases when the concentration of sucrose decreases or increases. In the case of the aluminum sensor, the maximum sensitivity and resolution are reached in the region of high values of sucrose concentration, whilst in the case of the silver sensor formed the maximum sensitivity is in the region of low values of sucrose concentration. [PERSON] [25] proposed a biosensor with optical fiber-based on nanoparticles of silver and modulated in intensity. The sensitivity of this sensor is 1.6 RIU\({}^{-1}\) and the resolution 4.68 \(\times\) 10\({}^{-3}\) RIU with a resolution of 0.75% of the photodetector. In our sensor, the resolution of our photodetector is 0.2%. Considering 0.2% in [PERSON]'s sensor, 1.2 \(\times\) 10\({}^{-3}\) RIU would be obtained, thus, comparing our sensor with [PERSON]'s sensor, the resolution of our aluminum sensor is better, and the silver sensor is the same in the zone of worst resolution and better in the other zones. We can compare our sensor with others based on absorbance, interrogation in angle, and interrogation in wavelength. [PERSON] et al. [8] proposed a plasmonic sensor based on absorbance. They obtained a resolution of 8.7 \(\times\) 10\({}^{-5}\) RIU, better than ours, due to the resolution of their spectrometer (0.0002), but not due to the sensor. Compared with sensors based on interrogation in wavelength or angular, we have better sensitivity and resolution than those based on wavelengths but worse than those based on the interrogation of angle [26]. The advantage, in our case, is that we use a simple photodetector for measuring instead of a spectrometer and we do not have to take a sample, we measure continuously. Comparing ranges, we can measure concentrations of up to 78% sucrose solution, a very long range compared with others which are considered to have a wide range [26] such as a range of 60%. Although the sensor designed by [PERSON] et al. [27] is not specifically for sucrose, when it works in amplitude interrogation, it has a maximum sensitivity of 93 RIU\({}^{-1}\) when the refractive indices are in the range 1.42-1.43, which are in the same order of magnitude as our maximum sensitivity. When compared with the glucose concentration measurement sensor from [PERSON] et al. [28] its maximum sensitivity is 14,847.03 RIU\({}^{-1}\) with analyte with a refractive index of 1.333 and 7351.82 RIU\({}^{-1}\) with analyte with a refractive index of 1.331,  
Figure 7: Reflectance curve vs. the concentration of sucrose.