Performance Enhancement of Photoconductive Antenna Using Saw-Toothed Plasmonic Contact Electrodes

Xingyun Zhang,Fangyuan Zhan,Wenlong He,Xianlong Wei,Cunjun Ruan

doi:10.3390/electronics10212693

Xingyun Zhang, Fangyuan Zhan + Show 3 more

Open Access

https://doi.org/10.3390/electronics10212693

Copy DOI

Abstract

A photoconductive logarithmic spiral antenna with saw-toothed plasmonic contact electrodes is proposed to provide a higher terahertz radiation compared with the conventional photoconductive antenna (PCA). The use of saw-toothed plasmonic contact electrodes creates a strong electric field between the anode and cathode, which generates a larger photocurrent and thereby effectively increases the terahertz radiation. The proposed PCA was fabricated and measured in response to an 80 fs optical pump from a fiber-based femtosecond laser with a wavelength of 780 nm. When the proposed antenna is loaded with an optical pump power of 20 mW and a bias voltage of 40 V, a broadband pulsed terahertz radiation in the frequency range of 0.1–2 THz was observed. Compared to the conventional PCA, the THz power measured by terahertz time domain spectroscopy (THz-TDS) increased by an average of 10.45 times.

Highlights

The terahertz (THz) band lies in the frequency range between the millimeter wave and far infrared, describing the electromagnetic spectrum ranges from 100 GHz (3 mm) to 10THz (30 μm) [1,2]
By using the saw-toothed plasmonic contact electrodes, a strong electric field can be formed between the anode and cathode of the proposed antenna, contributing to a larger terahertz radiation generated from the proposed photoconductive antenna (PCA)
A photoconductive terahertz emitter consists of an external optical pump, an antenna located on a photoconductor, and a bias voltage

Summary

Introduction

The terahertz (THz) band lies in the frequency range between the millimeter wave and far infrared, describing the electromagnetic spectrum ranges from 100 GHz (3 mm) to 10. Large-area photoconductive emitters based on plasmonic contact electrodes have been proposed to achieve high terahertz power levels [17]. The proposed LT-GaAs thin-film configuration was used to increase the number of photo-generated carriers, which contributed to a high optical-to-terahertz conversion efficiency. The plasmonic contact electrodes were introduced to generate high terahertz radiation power from a photoconductive terahertz emitter based on a bow-tie antenna [27] and logarithmic spiral antenna [28]. A broadband photoconductive logarithmic spiral antenna with sawtoothed plasmonic contact electrodes for THz generation enhancement is proposed. By using the saw-toothed plasmonic contact electrodes, a strong electric field can be formed between the anode and cathode of the proposed antenna, contributing to a larger terahertz radiation generated from the proposed PCA. The experimental results verify the broadband and enhanced THz radiation characteristics of the proposed antenna

Materials and Methods

3.3.Experiments

Photograph

Conclusions

5.18 V peak-to-peak