Efficiency of Photoconductive Terahertz Generation in Nitrogen-Doped Diamonds

Vitali V Kononenko,Pavel A Chizhov,Maxim S Komlenok,Andrey P Bolshakov,Vitaly I Konov,Andrey A Khomich,Sergey V Garnov,Vladislava V Bulgakova,Vladimir V Bukin

doi:10.3390/photonics9010018

Abstract

The efficiency of the generation of terahertz radiation from nitrogen-doped (∼0.1–100 ppm) diamonds was investigated. The synthetic polycrystalline and monocrystalline diamond substrates were pumped by a 400 nm femtosecond laser and tested for the photoconductive emitter operation. The dependency of the emitted THz power on the intensity of the optical excitation was measured. The nitrogen concentrations of the diamonds involved were measured from the optical absorbance, which was found to crucially depend on the synthesis technique. The observed correlation between the doping level and the level of the performance of diamond-based antennas demonstrates the prospects of doped diamond as a material for highly efficient large-aperture photoconductive antennas.

Highlights

Various techniques are used to generate THz radiation, including the acceleration of photoexcited carriers in photoconductive antennas (PCAs) [1], second-order nonlinear phenomena in electro-optical crystals [2] and laser-breakdown plasmas [3]
The observed correlation between the doping level and the level of the performance of diamond-based antennas demonstrates the prospects of doped diamond as a material for highly efficient large-aperture photoconductive antennas
This work investigated terahertz generation in PCAs based on nitrogendoped diamonds and pumped by the second harmonic of a Ti:sapphire laser

Summary

Introduction

Various techniques are used to generate THz radiation, including the acceleration of photoexcited carriers in photoconductive antennas (PCAs) [1], second-order nonlinear phenomena in electro-optical crystals (optical rectification) [2] and laser-breakdown plasmas [3]. PCAs pumped by femtosecond laser radiation are one of the most commonly used pulsed THz radiation sources [4,5]. The main features of the radiation generated by large-aperture PCAs are the low-frequency peak in the emission spectrum and the quasi-half-cycle pulse of the emitted radiation [6,7]. The study of promising substrate materials suitable for different pump lasers is of great interest for high-power large-aperture PCA devices [8,9,10,11,12,13]. Diamond has the highest dielectric strength out of all the THz-emitting substrates: its breakdown electric field was demonstrated to achieve 10 MV/cm [14]. The first diamond PCA was pumped by an excimer laser operated at 248 nm [8]. Femtosecond UV lasers are complex systems and can hardly be used to build table-top THz sources

Methods

Results

Conclusion