Abstract-Microfabrication of terahertz frequency-selective surface by short- and ultrashort laser ablation

Esakkimuthu Manikandan, Balakrishnapillai S. Sreeja, Sankararajan Radha, Muthukannan Duraiselvam, Abhishek Gupta, Shriganesh Prabhu,

https://www.spiedigitallibrary.org/journals/Optical-Engineering/volume-58/issue-1/011007/Microfabrication-of-terahertz-frequency-selective-surface-by-short--and/10.1117/1.OE.58.1.011007.short?SSO=1

This paper presents the method of fabricating a frequency-selective surface (FSS) filter for terahertz frequency by short- and ultrashort laser ablation process. The FSS consists of a capacitive screen made up of the copper metallic structure supported by a Teflon dielectric substrate. The dielectric properties of the Teflon substrate at terahertz frequencies were evaluated using THz-time-domain spectroscopy technique. The numerical simulation of the designed structure was performed using Computer Simulation Technology microwave studio software with unit cell configurations and the resonance was observed at 0.135 THz. The desired metallic microstructure was created in copper using an 8-ns solid-state Nd: YAG and 150 fs Ti:sapphire laser operating at the second harmonic wavelength of 532 and 800 nm, respectively. The proposed structure provides polarization-independent operation. The experimental verification of the fabricated FSS using femtosecond ablation process was done using THz-TDS technique, and it is observed that the measured data well match with the simulated result.

© 2018 Society of Photo-Optical Instrumentation Engineers (SPIE) 

Abstract-Enhanced optical-to-THz conversion efficiency of photoconductive antenna using dielectric nano-layer encapsulation

Abhishek Gupta, Goutam Rana, Arkabrata Bhattacharya, Abhishek Singh, Ravikumar Jain, Rudheer D. Bapat, S. P. Duttagupta,   S. S. Prabhu,

https://aip.scitation.org/doi/abs/10.1063/1.5021023


Photoconductive antennas (PCAs) are among the most conventional devices used for emission as well as detection of terahertz (THz) radiation. However, due to their low optical-to-THz conversion efficiencies, applications of these devices in out-of-laboratory conditions are limited. In this paper, we report several factors of enhancement in THz emission efficiency from conventional PCAs by coating a nano-layer of dielectric (TiO2) on the active area between the electrodes of a semi-insulating GaAs-based device. Extensive experiments were done to show the effect of thicknesses of the TiO2 layer on the THz power enhancement with different applied optical power and bias voltages. Multiphysics simulations were performed to elucidate the underlying physics behind the enhancement of efficiency of the PCA. Additionally, this layer increases the robustness of the electrode gaps of the PCAs with high electrical insulation as well as protect it from external dust particles.