Abstract-High power T-ray generation using a new array of photoconductive antennas

Hamid Reza Zangeneh,  Farzad Moradiannejad


https://www.sciencedirect.com/science/article/pii/S1434841118334046

In this work, a new array of photoconductive antennas is proposed as a high power T-ray source. The array was modeled and simulated by the finite difference time domain method. The structure and characteristics of the T-ray source were studied. The potential advantages of the proposed array include enhanced efficiency of the broadband THz radiation and confined radiated THz pulse. Also, an asymmetry in the design of the array allows optimizing high optical-to-terahertz conversion efficiencies. These potential advantages of the proposed array can be exploited in satellite telecommunications such as geostationary terahertz satellite links. Moreover, the array is capable of employing radiation-band shaping technique for generation of tunable and narrow-band THz radiation.

Abstract-Nanostructure‐Enhanced Photoconductive Terahertz Emission and Detection

Nezih Tolga Yardimci,  Mona Jarrahi, 

https://onlinelibrary.wiley.com/doi/abs/10.1002/smll.201802437

Photoconductive antennas are commonly used for terahertz wave generation and detection. However, their relatively low radiation power and detection sensitivity often place limitations on the signal‐to‐noise ratio and operation bandwidth of terahertz imaging and spectroscopy systems. Several different techniques are attempted to address these limitations. The most promising ones take advantage of the unique tools provided by nanotechnology. In this review, the recent nanotechnology‐enabled advances in photoconductive antennas, which use nanostructures, such as optical nanoantennas, plasmonic structures, and optical nanocavities, to increase the interaction of the optical pump beam with the photoconductive semiconductor, are discussed. All of these techniques are experimentally demonstrated to be efficient tools for enhancing the performance of photoconductive antennas for terahertz wave generation and detection.

Abstract-Photoconductive antennas based on epitaxial films In0.5Ga0.5As on GaAs (1 1 1)A and (1 0 0) substrates with a metamorphic buffer

K A Kuznetsov, G B Galiev, G Kh Kitaeva, V V Kornienko, E A Klimov, A N Klochkov, A A Leontyev, S S Pushkarev, P P Maltsev

http://iopscience.iop.org/article/10.1088/1555-6611/aabd5a/pdf

The terahertz (THz) wave generation by the spiral photoconductive antennas fabricated on the low-temperature and high-temperature grown undoped and Si-doped In0.5Ga0.5As films is studied by the terahertz time-domain spectroscopy method. The In0.5Ga0.5As layers were grown by molecular beam epitaxy on GaAs substrates with (1 0 0) and (1 1 1)A crystallographic orientations utilizing step-graded In x Ga1−x As metamorphic buffer. The antennas are excited by radiation of Er3+-fiber laser at 1.56 μm wavelength in two regimes: with pulse durations of 2.5 ps or 100 fs. It is found that the THz wave generation is 3–4 times more effective in the case of InGaAs-based antennas on (1 1 1)A GaAs substrates as compared to the (1 0 0) substrates. Power-voltage characteristic of the LT-InGaAs antenna up to and beyond threshold breakdown voltage are reported.

Abstract-Enhanced optical-to-THz conversion efficiency of photoconductive antenna using dielectric nano-layer encapsulation

Abhishek Gupta, Goutam Rana, Arkabrata Bhattacharya, Abhishek Singh, Ravikumar Jain, Rudheer D. Bapat, S. P. Duttagupta,   S. S. Prabhu,

https://aip.scitation.org/doi/abs/10.1063/1.5021023


Photoconductive antennas (PCAs) are among the most conventional devices used for emission as well as detection of terahertz (THz) radiation. However, due to their low optical-to-THz conversion efficiencies, applications of these devices in out-of-laboratory conditions are limited. In this paper, we report several factors of enhancement in THz emission efficiency from conventional PCAs by coating a nano-layer of dielectric (TiO2) on the active area between the electrodes of a semi-insulating GaAs-based device. Extensive experiments were done to show the effect of thicknesses of the TiO2 layer on the THz power enhancement with different applied optical power and bias voltages. Multiphysics simulations were performed to elucidate the underlying physics behind the enhancement of efficiency of the PCA. Additionally, this layer increases the robustness of the electrode gaps of the PCAs with high electrical insulation as well as protect it from external dust particles.

Abstract-Magnetic Field-Assisted Radiation Enhancement From a Large Aperture Photoconductive Antenna

Jitendra Prajapati,  Mrinmoy Bharadwaj,  Amitabh Chatterjee,  Ratnajit Bhattacharjee

http://ieeexplore.ieee.org/document/8244250/

The generation of terahertz radiation using photoconductive antennas is becoming very popular. Several experimental and simulation studies have been performed to study the characteristics of the photoconductive antenna (PCA). Although various methods have been proposed to increase the radiated power from it, the radiated power remains very low. In this paper, we present an analytical study of improving the radiated power from a large aperture PCA using an external magnetic field source. The transit time behavior of the carriers is computed using the basic semiconductor carrier dynamics model, including the transient mobilities with the dependencies on the electric field and carrier’s concentration. Analytical studies show that substantial enhancement in the radiated field can be achieved when such external magnetic field is applied. Furthermore, the polarity of the radiated field depends on the orientation of the applied magnetic field. The results obtained from analytical calculations exhibit similar behavior as reported in some experimental results.

Abstract- Photoconductivity of an InAs/GaAs self-assembled quantum dot photoconductive THz antenna

Amit Yadav,  Andrei Gorodetsky,  Eugene Avrutin, Ksenia A. Fedorova,  Edik U. Rafailov

http://ieeexplore.ieee.org/document/8086621/


A broadband terahertz (THz) source is desirable for applications such as imaging, spectroscopy and security. Towards this, an InAs/GaAs quantum dot (QD) based photoconductive antenna (PCA) is a promising and compact solution for THz generation. Coherent THz radiation in the pulsed and the CW regime has been generated with a QD PCA under a resonant and off-resonant pumps [1, 2]. While photoconductivity of QD materials in mid- and far-IR at lower temperatures has been studied for cryogenic sensors and attributed to interlevel transitions, near-IE interband photoconductivity needs further investigation [3, 4]. In this work, we report on the photoconductive properties of an InAs/GaAs QD PCA pumped by a broadly-tunable InAs/GaAs QD external-cavity diode laser.

Abstract-CBRN Defense Using THz Pulse Trains from Semiconductor Disk Lasers

Esa J. Saarinen, Jari Lyytikäinen, Sanna Ranta

https://link.springer.com/chapter/10.1007/978-94-024-1093-8_19

We propose THz generation from a photoconductive antenna illuminated by a train of optical pulses with a pulse repetition rate that corresponds to the desired THz frequency. This new method of THz generation can be seen as a hybrid between the conventional optical THz generation methods, where the optical source is either a heterodyne signal from two continuous wave lasers or a single short pulse. Therefore, the method holds promise for generating both coherent broadband and narrow-linewidth continuous wave THz radiation. The high-repetition rate optical pulse train is obtained from a semiconductor disk laser harmonically mode-locked by a semiconductor saturable absorber mirror and an intracavity etalon. Optical pulse trains with pulse repetition rates from 190 GHz to 580 GHz are demonstrated at an average optical output power of 1 W. This power level is enough for driving full arrays of photoconductive antennas. The approach may provide a compact and powerful THz source for CBRN defense.

Abstract-Plasmon-enhanced LT-GaAs/AlAs heterostructure photoconductive antennas for sub-bandgap terahertz generation

Afshin Jooshesh, Faezeh Fesharaki, Vahid Bahrami-Yekta, Mahsa Mahtab, Thomas Tiedje, Thomas E. Darcie, and Reuven Gordon

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-18-22140

Photocurrent generation in low-temperature-grown GaAs (LT-GaAs) has been significantly improved by growing a thin AlAs isolation layer between the LT-GaAs layer and semi-insulating (SI)-GaAs substrate. The AlAs layer allows greater arsenic incorporation into the LT-GaAs layer, prevents current diffusion into the GaAs substrate, and provides optical back-reflection that enhances below bandgap terahertz generation. Our plasmon-enhanced LT-GaAs/AlAs photoconductive antennas provide 4.5 THz bandwidth and 75 dB signal-to-noise ratio (SNR) under 50 mW of 1570 nm excitation, whereas the structure without the AlAs layer gives 3 THz bandwidth, 65 dB SNR for the same conditions.

© 2017 Optical Society of America

Abstract-Enhanced Terahertz Radiation Generation of Photoconductive Antennas Based on Manganese Ferrite Nanoparticles

• Weien Lai
• , Oday Mazin Abdulmunem
• , Pablo del Pino
• , Beatriz Pelaz
• , Wolfgang J. Parak
• , Qian Zhang
•  & Huaiwu Zhang
• • 
    
  • http://www.nature.com/articles/srep46261

This paper presents a significant effect of manganese ferrite nanoparticles (MnFe2O4 NPs) on the increase of the surface photoconductivity of semiconductors. Herein, the optical characterization of photo-excited carriers of silicon coated with MnFe2O4 NPs was studied by using THz time-domain spectroscopy (THz-TDs). We observed that silicon coated with MnFe2O4 NPs provided a significantly enhanced attenuation of THz radiation in comparison with bare silicon substrates under laser irradiation. The experimental results were assessed in the context of a surface band structure model of semiconductors. In addition, photoconductive antennas coated with MnFe2O4 NPs significantly improved the efficiency of THz radiation generation and signal to noise ratio of the THz signal. This work demonstrates that coating with MnFe2O4 NPs could improve the overall performance of THz systems, and MnFe2O4 NPs could be further used for the implementation of novel optical devices.