## 1 Introduction  
The configurations first proposed by [PERSON] [1] and [PERSON] [2] to couple incidence light to surface plasmon modes at a metal-air interface renewed the challenges and emerging direction in the area of sensors. Thus, in the 1980s, the successful achievement of both gas detection and biomolecular sensing based on surface plasmons in a Kretchmann configuration was reported [3]. At present, surface plasmon resonance (SPR) based sensors are an important part of different domains such as analytical chemistry, biology, and diagnostics due to their high sensitivity which eliminates the labeling process and could alter the properties of the molecules and also the possibility of real-time monitoring of the interactions involved in kinetic studies. The increased detection performance derives from the extremely sensitive reflectivity of the thin metal film with optical variations (refractive index changes) of the medium placed on one side of it. However, as the high sensing performance drastically degrades when low mass analytes are used [4], the simple SPR sensor configuration has been continually adjusted to allow single molecule detection [5], prenatal diagnostics [6], food safety [7] and temperature sensing [8]. It has been shown that by adding a thin semiconductor layer on top of the metal, the overall performance of a sensor can be improved [9]. Moreover, this film acts as a protective coating when silver is used as plasmonic metal, improving its chemical stability [10]. However, although the sensitivity is enhanced, in comparison to a classic structure, the response becomes broader as a result of the thickness of the dielectric and its inherent absorption [11]. This problem has been overcome using graphene monolayers with improved light absorption [12] that also increases the biological compatibility [13]. However, the semiconductor's thickness and the number of graphene monolayers have to be carefully chosen to attain a good performance. Newly emerging graphene 2D materials which are made up of transition metal dichalcogenide monolayers (TMDC), such as MoS\({}_{2}\), WS\({}_{2}\), etc., have also been utilized in SPR sensor design to improve their performance [11; 14; 15]. Similar to graphene monolayers, MoS\({}_{2}\) and WS\({}_{2}\) provide a high affinity for a wide range of target molecules due to their hydrophobic nature [16; 17]. The biocompatibility of the 2D materials (Graphene, MoS\({}_{2}\) and WS\({}_{2}\)) used here has been extensively studied in the literature [18; 19; 20]. Various biosensors and immunosensors with a great performance based on these 2D materials have been proposed such as: dopamine, ascorbic acid and uric acid detection sensors [21]; single strand DNA (ssDNA) interaction sensors [22]; and sensors used in the detection of prostate-specific antigens [23]. Furthermore, the main drawback of graphene coated sensors is that the increased overall absorption with the number of monolayers added, could be overcome by using these new materials as they show a high absorption for only one monolayer [24; 25; 26]. Recently, more complex configurations based on metal-semiconductor/2D material-metal-2D material [27] and even semiconductor-metal-dielectric-2D material contacts [28] have been developed. For these architectures, the conventional method of varying each layer's thickness has become almost impossible due to the size of the design space (i.e., thickness of the metallic layer, number of monolayers). Design optimization studies have been performed with promising results using algorithms that are inspired by nature, such as particle swarm optimization [29; 30] or genetic algorithms [31]. Whereas genetic algorithms mimic natural evolution, the particle swarm optimization process is ispired by bird flock movements, and have been employed to further improve the graphene [31] or TMDC based SPR sensor's performance [32] or to discover new configurations regarding the plasmonic platform material [31].