Terahertz pulse generation and detection with LT-GaAs photoconductive antenna (original) (raw)
Related papers
Broadband THz Generation from Photoconductive Antenna
Since the observation of radiation in the Terahertz (THz) frequency range from photoconductive antennas exited by femtosecond (fs) laser pulses, considerable efforts have been made to understand the mechanism responsible for THz generation, and to develop applications in THz Time-Domain Spectroscopy (THz-TDS). In this paper, the calculation of THz radiation from biased photoconductive antenna is reported, given some amelioration of the calculation model and classical Drude-Lorentz theory. Some simulation results based on the new calculation model are shown.
KnE Energy, 2018
The design and technological conditions for manufacturing photoconductive antennas based on low-temperature-grown gallium arsenide (LT-GaAs) have been developed. An optimized photoconductive THz antenna based on LT-GaAs with flag geometry of the contacts was fabricated. LT-GaAs samples were obtained by molecular-beamepitaxy at temperatures of 230 ∘ C on GaAs (100) substrates. On an optical setup with a femtosecond titanium-sapphire laser, a volt (watt)-ampere characteristics and photocurrent efficiency of the photo-conductive antenna measured by the pyroelectric sensor. The optimum annealing temperature of LT-GaAs was determined for generation of intense THz radiation. PCA have been tested in the terahertz radiation generation. The substantial effect of water vapor in the air and the environment of transparent objects is THz. The useful terahertz bandwidth extends from 0.1 to 2.7 THz and the source of terahertz wave is the most commonly used nonlinear crystal ZnTe in the biomedicine applications. However, in comparison PCA on LT-GaAs with ZnTe have better results in the intensity and the power of the THz response. Therefore, it will be possible to detect a lower concentration of biological objects.
ETRI Journal, 2014
In this letter, we present low-temperature grown GaAs (LTG-GaAs)-based photoconductive antennas for the generation and detection of terahertz (THz) waves. The growth of LTG-GaAs and the annealing temperatures are systematically discussed based on the material characteristics and the properties of THz emission and detection. The optimum annealing temperature depends on the growth temperature, which turns out to be 540°C to 580°C for the initial excess arsenic density of 2×10 19 /cm 3 to 8×10 19 /cm 3 .
Materials Research Bulletin, 2019
This work reports on an advanced approach to the design of THz photoconductive. antenna (PCA). The LT-GaAs thin films used for the PCA fabrication were synthesized by MBE method on GaAs (100) substrate by adjusting the As pressure, As/Ga fluxes ratio, growth/annealing temperatures and annealing time. These parameters crucially affect electro-optical properties of the PCA samples as evidenced by the THz radiation power and timedomain spectroscopy measurements. The annealing temperature of 670°C was found to be optimal for constructing a PCA possessing high amplitude of the THz radiation over the spectral range up to 1 THz at the resonance of 0.1 THz. The comparison of this PCA with the reference ZnTe crystal reveals a 2-fold increase in THz power. Furthermore, this antenna attains a 1.5-, 3-, and 2-fold increase in THz power, photocurrent efficiency, and actuating dc BV, as compared with the commercial ZOMEGA antenna. These results pave the way towards the creation of highly efficient LT-GaAs-based PCAs.
Vertical versus planar pulsed photoconductive antennas that emit in the terahertz regime
Optik, 2018
The design process of a photoconductive antenna (PCA), which emits efficiently in the electromagnetic terahertz range, demands some considerations that are discussed through this work. In this work, several essential characteristics of a photoconductive antenna made with LT-GaAS are studied by means of well established commercial software (COMSOL 5.3 [1]). An approach to the efficiency is also made through the study of geometry, the laser illumination position, the substrate doping distribution, the direction of the bias applied to the semiconductor, the matching impedance at the laser operating frequency and, finally, the plasmonics effects or penetration laser enhancement due to the use of nano antennas. We study and compare two kinds of structures, one which is quasi-bidimensional or planar and the other which is vertical. Additionally, the photoconductive antennas are also modeled by using a simplified equivalent circuit which helps to understand the antennas' performance. Therefore some fundamental parameters, like the transient capacitance between the metal contacts are also studied. Furthermore, we introduce an optimized vertical design which achieves the best results.
Pulsed photoconductive antenna terahertz sources made on ion-implanted GaAs substrates
In this work we show that improved performances of terahertz emitters can be obtained using an ion implantation process. Our photoconductive materials consist of high-resistivity GaAs substrates. Terahertz pulses are generated by exciting our devices with ultrashort near-infrared laser pulses. The ion implantation introduces non-radiative centres, which reduce the carrier lifetime in GaAs. The presence of the charged defects also induces a redistribution of the electric field between the antenna electrodes. This effect has a huge influence on the amplitude of the radiated terahertz field. Results obtained as a function of the laser excitation power are discussed and a comparison of the performance of these devices with a conventional antenna-type emitter is given.
Optics Letters, 2007
The generation of terahertz (THz) transients in photoconductive emitters has been studied by varying the spatial extent and density of the optically excited photocarriers in asymmetrically excited, biased lowtemperature-grown GaAs antenna structures. We find a pronounced dependence of the THz pulse intensity and broadband ͑Ͼ6.0 THz͒ spectral distribution on the pump excitation density and simulate this with a three-dimensional carrier dynamics model. We attribute the observed variation in THz emission to changes in the strength of the screening field.
Journal of Infrared, Millimeter, and Terahertz Waves, 2017
We investigate the influence of the surface properties of a low-temperature-grown GaAs photoconductive antenna on the terahertz (THz) emission strength, using a specially designed THz time-domain spectroscopy system. The system allows us to excite six different positions along the 10 μm gap of a coplanar stripline antenna with a length of 10 mm without changing the alignment of the optical or THz beam path. A comparison to the surface roughness and the grain size which are extracted from an atomic force and a scanning electron microscope is given.
Generation and detection of terahertz pulses from biased semiconductor antennas
Journal of the Optical Society of America B, 1996
We propose a simple model based on the Drude-Lorentz theory of carrier transport to account for the details of the ultrashort terahertz pulses radiated from small photoconductive semiconductor antennas. The dynamics of the bias field under the influence of the space-charge field from the accelerated carriers is included in the model. We consider in detail the optical system used to image the terahertz radiation onto the terahertz detector, and we calculate the frequency-dependent response of the detector. The proposed model is compared with several different experiments, each focusing on different parameters of the model. Agreement between experiment and model is found in all cases, supporting the validity of this simple and appropriate model.