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A new metal-semiconductor-metal photodetector (MSM-PD) based on a hybrid plasmonic and extra ordinary transmission (EOT) phenomenon is proposed. In the designed structure, we demonstrate that light transmission is improved by means of a new shape of surface nanograting and by optimizing the physical parameters of the metal. In this work the optical transfer parameters are strongly interrelated and all the parameters are optimized and the light transmission is enhanced by 55 times compared to the reference structure. Furthermore, the output port of the subwavelength slit in the presented MSM-PD has a dual horn shape and improves absorption light in the active layer of the structure. Also, by filling this port with the same type of material as that of the active layer, the absorption becomes greater than before. Moreover, the confinement region of the light in the active layer is reduced by using the hybrid plasmonic effect and therefore, the probability of the photon absorption is 101 times greater than that of the reference structure. Thus, the transmission and absorption enhancement improves the quantum efficiency and the electrical response of the presented MSM-PD. A high performance new photodetector is identified as an ultra-fast MSM-PD and because of its thin film active layer can be used as a low-noise one.

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We investigate the influence of non-Hermiticity on the adiabatic elimination in coupled waveguides. We show that adiabatic elimination is not affected when the system is in parity-time symmetric phase. However, in the broken phase the eliminated waveguide loses its darkness namely its amplitude starts increasing, which means adiabatic elimination does not hold in the broken phase. Our results can advance the control of the dynamics in coupled laser cavities, and help the design of controllable absorbers. [14][15][16]. Among the non-Hermitian systems, Parity and Time reversal (PT) symmetric systems are specifically important because of showing phase transition from the exact phase with real spectrum to the broken phase with complex spectrum [17]. The transition point is known as exceptional point or PT symmetry breaking point. At the exceptional point two or more eigenvectors of the system in a pairwise manner coalesce and their associated eigenvalues become degenerate. In each phase, many interesting features have been discovered and experimentally demonstrated. Among them are unidirectional invisibility [18,19], parity anomaly [20], loss induced lasing [21], protected bound state [22,23], and non-Hermiticity induced flat band [8].

In this work, we propose and evaluate a novel non-planar design of a doublestage phononic crystal (PnC) consisting of a Si substrate, a bottom layer of ZnO, Si pillars and another ZnO layer on top of the pillars. The proposed double-stage PnC exhibits interesting properties such as routing of incoming elastic wave based on source polarization and frequency. In addition, the elastic energy profile of the surface coupled modes are distributed between surface layers including two ZnO layers and pillars dividing the incoming elastic wave between top and bottom ZnO layers. Therefore, the proposed doublestage PnC can be considered as a building block in the design of a super-sensitive structure. The top ZnO layer's conductivity is modulated based on acoustoelectric effect when exposed to an external excitation like UV light illumination and environmental gases such as hydrogen. The proposed super-sensitive device, benefits from higher coupling between local resonators and therefore, the higher phase change between two branches of the elastic Mach-Zehnder which leads to a sensitivity and transmission as high as 23 and -8 dB at 8.6 GHz. Moreover, the proposed elastic Mach-Zehnder has the advantage of avoiding the non-sensing parts such as bottom ZnO layer as the reference branch, pillars and substrate to be affected by the external excitation due to the vertical configuration.