Intense sub-terahertz radiation from wide-bandgap semiconductor based large-aperture photoconductive antennas pumped by UV lasers

Abstract

The characteristics of terahertz (THz) radiation generated from large-aperture photoconductive antennas (LAPCAs) were investigated. The antennas were fabricated using different wide-bandgap semiconductor crystals (ZnSe, GaN, 6H-SiC, 4H-SiC and β-Ga 2 O 3 ) as the substrate. We used an amplified sub-picosecond KrF excimer laser for illumination of the LAPCAs. THz emission scaling was studied as a function of the bias field and the pump laser energy. It was found that the radiated THz energy scales quadratically as a function of the bias field and sub-linearly as a function of the optical fluence for most of the substrates. Further, we demonstrate that SiC, and especially 4H-SiC LAPCAs offer the best THz generation performances. In order to generate intense THz radiation, we fabricated both 6H-and 4H-SiC LAPCAs with an interdigitated structure. From the field autocorrelation trace, it was found that the spectra lie in the sub-THz regime, extending up to 400 GHz, with a peak frequency at 50 GHz, making the bridge between the microwaves band and the THz band. The maximum generated THz energy was 11 μJ, which is to date the highest THz energy measured from LAPCA sources, with a corresponding peak electric field of 115 kV cm −1 and a corresponding ponderomotive potential of 60 eV. Nonlinear THz experiments were performed using these energetic THz pulses, and open aperture Z-scan experiments in an n-doped InGaAs layer revealed a transmission enhancement of 1.7. It was also shown that in order to have efficient THz generation, the energy contrast of the laser must be kept high.

1.4‐mJ High Energy Terahertz Radiation from Lithium Niobates

“…These data are referenced from previous record results of THz sources based on solid plasma, [ 14 ] liquid plasma, [ 18 ] gas plasma, [ 12 ] optical rectification from ZnTe, [ 68 ] and organic crystals, [ 52 ] different frequency generation in PPLNs, [ 16 ] accelerators, [ 69 ] and photoconductive antennas. [ 70 ]…”

Hybrid Perovskite Terahertz Photoconductive Antenna

“…Under 800 nm excitation, THz pulses with similar waveforms and spectra were also obtained from an MAPbI 3 -based LAPCA. The obtained waveforms are typical for photoconductive antennas with a large interelectrode distance [ 19 ]. It is important to note that in such geometry of emitter, the temporal profile of the THz pulse is determined by the interelectrode distance rather than by the lifetime of the carriers in the photoconductive substrate.…”

“…Photoconductive antennas are promising sources of THz radiation due to their compactness, relatively high power, and narrow directivity of the output radiation [ 19 ]. Moreover, LAPCAs are unique sources of quasi half-cycle (unipolar) THz pulses covering the lower part of the THz spectrum ranging from 0.1 to 1 THz suitable for experiments on the acceleration of charged particles and electrons [ 20 , 21 ].…”

Efficiency of Photoconductive Terahertz Generation in Nitrogen-Doped Diamonds

“…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]. Currently, 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].…”