Abstract-Improving Unbiased Terahertz Photoconductive Antenna Based on Dissimilar Schottky Barriers Using Plasmonic Mode Excitation

Saman Ghorbani, Mohammad Bashipour, Mohammadreza Kolahdouz,



https://www.sciencedirect.com/science/article/pii/S0030402619308526

A new design for an unbiased antennaless terahertz (THz) photoconductive antenna (PCA) using an array of bimetallic nanostructures located underneath the low temperature gallium arsenide (LT-GaAs) layer is designed and proposed which is highly under focus for THz imaging applications. Each element of array consists an asymmetric metal-semiconductor-metal (MSM) structure with dissimilar Schottky barriers. Simulation results demonstrated that by irradiating this structure using 800 nm femtosecond laser, THz field as high as a conventional biased PCA can be generated. Finite element method was used to optimize the PCA’s geometrical parameters through solving the Maxwell’s equation in combination with drift-diffusion/Poisson’s equations. According to the simulation results, by optimizing the array’s periodicity, width and height of the proposed bimetallic nanostructures, plasmonic resonant cavity mode between two adjacent nanostructures enhances the optical absorption and so, the transient photocurrent. Transient photocurrent of 45 µA was obtained that is 29% higher than the one from the conventional biased PCA.

Abstract-Thin Film Tandem Nanoplasmonic Photoconductive Antenna for High Performance Terahertz Detection

Saman Ghorbani, 

Mohammad Bashirpour, 

Jafar Poursafar, 

Mohammadreza Kolahdouz, 

Mohammad Neshat, 

Amirali Valinejad

https://www.sciencedirect.com/science/article/pii/S0749603618309352
Photoconductive antennas (PCA) have attracted lots of attention for terahertz application, due to their room temperature operation and compact design. On the other hand, their main problem is acquiring low output power. Lately, plasmonic structures of different geometries have been proposed to overcome the mentioned issue. Here, we have proposed and simulated a PCA on a silicon-on-sapphire substrate and a layout of a plasmonic nanostructure in which the effect of geometrical parameters of the nanostructure on PCA’s output was investigated and optimized. According to the results for one layer plasmonic nanostructure, two different geometries showed more than 700% improvement in the device photocurrent which are related to different types of surface plasmons. By combining these layouts and benefiting from both simultaneously, a final proposed nanostructure was constructed. After optimizing the new structure’s parameters, a significant increase of 15400% in photocurrent enhancement was achieved by comparing to the conventional THz PCAs on similar substrate.