Efficiency of Photoconductive Terahertz Generation in Nitrogen-Doped Diamonds

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.

CVD Encapsulation of Laser-Graphitized Electrodes in Diamond Electro-Optical Devices

“…Diamond is a unique material with a number of record-breaking properties. Its electrical breakdown threshold is up to 2-10 MV/cm [1][2][3], making it attractive for highvoltage applications, such as field electron transistors [4][5][6][7][8], switching diodes [9][10][11][12][13], highenergy particle trapping [14][15][16][17][18], photoconductive antennas [19][20][21][22] and others. The thermal conductivity of diamond (24 W/cm•K) [23] is even higher than that of copper, which allows it to effectively dissipate heat [24][25][26][27][28].…”

“…Recently, this field has received a new impetus. Diamond doping allowed the use of commercially available IR fs-laser sources for the optical pumping of PCAs [21,22] instead of the complex UV fs-lasers that would have to be used to generate the photocarriers in pure diamond. However, the demonstrated power of the generated THz radiation is still far from the maximum available.…”

“…They grew the polycrystalline film covering the Pt-patterned diamond surface. Polycrystalline wafers were found to be ineffective in terms of THz generation [21]. Therefore, in this work, we studied the possibility of epitaxially growing single-crystal diamond above the conductive structures.…”

A Diamond Terahertz Large Aperture Photoconductive Antenna Biased by a Longitudinal Field

“…The doping introduces optical defects into the crystals and results in the appearance of ∼2.2 eV electron transitions from the defect levels to the conduction bands [23]. Thus, doped diamond PCAs have been adapted to operate with the second harmonic of commercial Ti:sapphire lasers and have demonstrated an emitted energy of 0.2-0.3 nJ at a bias field of 25 kV/cm [24].…”

Cleavage-Driven Laser Writing in Monocrystalline Diamond

“…The unique properties of this crystal make it one of the most promising materials for radiation detectors [2], heat sinks [3], photonic mediums [4,5], Raman lasers [6], information storage [7], etc. Quite recently, nitrogen-doped diamonds were shown to operate effectively as photoconductive antennas (PCA) emitting terahertz (THz) pulses under 400 nm femtosecond pumping [8,9]. In light of the record dielectric strength and thermal conductivity, diamond seems a prospective candidate for high-power and high-intensity THz emitters.…”