LAUSR

In this paper, an optical absorber based is exploited on self-similar cylindrical for material detection in the infrared spectrum as a refractive index sensor. Two models are suggested and the effect of the gaps is discussed. Actually, the gaps can be used for intensifying the absorption and improving the figure of merit (FOM). The absorber is modified for 300 THz (1000 nm) with reflection value of − 45 dB (0.004) which is made this absorber as a good choice for optical refractive sensing. This study shows the importance of the parasitic elements and gaps for improving the sensing quality and FOM value. In fact, the reflection of the Nanoabsorber is increased extremely without using the parasitic element up to − 14 dB. As shown in this paper, the FOM of the prototype absorber is enhanced more than 10 times for some refractive indexes by implementing of gaps. The maximum value of the FOM is 400 RIU −1 for the final model with gap and the maximum sensitivity is 204 nm/RIU obtained for the structure without the gap. In brief, these gaps can be considered for increasing the FOM more than the basic model.