Architectures. This section describes how a set of elements can be structured in order to model a CPS, its parts, and its surroundings. Similar to e.g. [29, 34], such a structure will be referred to as an architecture, which, in this paper, will be denoted with the symbol A . In contrast to other contract theories, e.g. [6–8], the present paper focuses more on the structuring of elements and on the sharing of port variables. A well-defined structure of how ports are shared is needed in order to define scoping constraints for environment-centric contracts in Sec. 3.2. Prior to presenting the formal definition of an architecture, the concept is introduced informally by describing an architecture ALM−sys of a ”Level Meter system” (LM-system) ELM−sys, as shown in Fig. 2a where an element is repre- sented as a rectangle filled with gray with boxes on its edges that symbolize its port variables and in Fig. 2b where the hierarchical structure of the LM-system is shown as a tree. As shown in Fig. 2a, the LM-system ELM−sys consists of a tank Etank and an electric-system EE−sys. The electric-system EE−sys consists of the potentiometer Epot as described in Sec. 2.2, a battery Ebat and a level meter ElMeter. The slider h is connected to a ”floater”, trailing the level f in the tank. In this way, the potentiometer Epot is used as a level sensor to estimate the level in the tank. The estimated level is presented by the level meter ElMeter where l denotes the presented level.
Architectures. Concerning the optoplasmonic chip assembling, as defined in the specifications of D1.1, two main strategies are considered: M1 “Semitransparent Drain” and M2 “Reflective encapsulation”. According to strategy M1, the light generated by the OLET should reach the above-positioned nanoplasmonic grating, then modulated and back directed to the OPD, which is placed onto the OLET source electrode. A semi-transparent drain is therefore required for the OLET. In this regard, top-emitting devices have been developed. As preliminary approach, the protocol followed at CNR consisted in keeping constant the device structure while using a drain electrode as thin as possible. Option #3 (766-nm emitting structure) was selected as benchmark OLET and different silver thicknesses of the drain electrode have been investigated. The use of a 14 nm-thick Ag electrode resulted in OLETs with similar characteristics to those already reported in Figure 7, with µh 10-1 cm2V-1s-1, Vth - 40 V and ION/IOFF 105. Despite the use of a thin silver layer as drain electrode, the OLET optical power resulted relatively low, with values of 150 nW from the OLET top side and 800 nW from the bottom side. In sight of this, the Ag thickness has been tuned and the optimized-drain layer, in terms of optoelectronic FOMs of the OLETs, resulted 20 nm-thick. Indeed, as shown in Figure 8b, electrical characteristics and optical power (measured from the bottom side of the OLETs) were similar to those of reference devices. In addition, the OLET optical power measured from the top side (Figure 8a) resulted only one order of magnitude lower than the corresponding optical power measured from the bottom side (at VDS = -100V, VGS = -100 V, optical power 500 nW and 5 µW when measured from the top and bottom OLET side, respectively) and three-times- higher than the optical power (measured from the top side) using 14 nm of Ag-drain. Despite top-emitting OLETs can be further improved in terms of optical power, these preliminary tests highlight that both M1 and M2 strategies can be pursued if needed in view of the optoplasmonic chip assembling.
