Magnetic Field-Assisted Radiation Enhancement From a Large Aperture Photoconductive Antenna
TL;DR: In this paper, the authors presented an analytical study of improving the radiated power from a large aperture PCA using an external magnetic field source, including the transient mobilities with the dependencies on the electric field and carrier concentration.
Abstract: 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.
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TL;DR: In this article, the saturation properties and power scaling of large-aperture planar photoconducting antennas with different semiconductor materials have been discussed, and the amplitude of the radiated electric field saturates at a value comparable to the bias field in agreement with a simple model of the radiation.
Abstract: We describe the saturation properties and power scaling of large-aperture planar photoconducting antennas. These antennas have been used to emit and detect electromagnetic pulses with terahertz bandwidth. At high optical fluences, the amplitude of the radiated electric field saturates, at a value comparable to the bias field in agreement with a simple model of the radiation. We also discuss the saturation properties of the large-aperture photoconducting antennas with different semiconductor materials.
228 citations
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TL;DR: In this article, the authors review the past and recent works on generating intense terahertz (THz) pulses from photoconductive antennas (PCAs) and focus on two types of LAPCA that can generate high-intensity THz pulses: those with large-aperture dipoles and those with interdigitated electrodes.
Abstract: In this paper, we review the past and recent works on generating intense terahertz (THz) pulses from photoconductive antennas (PCAs). We will focus on two types of large-aperture photoconductive antenna (LAPCA) that can generate high-intensity THz pulses (a) those with large-aperture dipoles and (b) those with interdigitated electrodes. We will first describe the principles of THz generation from PCAs. The critical parameters for improving the peak intensity of THz radiation from LAPCAs are summarized. We will then describe the saturation and limitation process of LAPCAs along with the advantages and disadvantages of working with wide-bandgap semiconductor substrates. Then, we will explain the evolution of LAPCA with interdigitated electrodes, which allows one to reduce the photoconductive gap size, and thus obtain higher bias fields while applying lower voltages. We will also describe recent achievements in intense THz pulses generated by interdigitated LAPCAs based on wide-bandgap semiconductors driven by amplified lasers. Finally, we will discuss the future perspectives of THz pulse generation using LAPCAs.
3 citations
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TL;DR: In this article, a plasmonic resonator antenna is designed to operate at the lower terahertz (THz) frequency band of 0.5-5 GHz.
Abstract: A plasmonic resonator antenna is designed to operate at the lower terahertz (THz) frequency band of 0.5–5 THz. A very thin layer of graphene film about 0.34 nm is employed as the radiating patch. The resonant frequency of the antenna is controlled by tuning the chemical potential of the graphene layer. As the chemical potential of the antenna is varied from 0 eV to 2 eV, we achieve additional resonant modes leading to triple band operation. At a fixed chemical potential of 2 eV, quad band operation is realized for a substrate thickness of 45 μm. It is inferred that, the operating frequency of the antenna can be varied based on the requirement, by tuning the chemical potential of the graphene layer and by modifying the substrate thickness. For the single band antenna operation, a maximum gain of 2.58 dB and directivity of 2.89 dBi is obtained at 2.58 THz. In the case of triple band operation, a maximum gain of 1.22 dB and directivity of 3.66 dBi is obtained at 4.41 THz. Further, quad band operation is achieved at 1.73 THz, 2.6 THz, 4.01 THz and 4.72 THz, with a maximum gain of 1.61 dB and a directivity of 7.17dBi at 4.72 THz. Further, the effect of chemical potential on the main lobe direction of the radiation pattern, leading to beam steering, is also investigated for the first time.
3 citations
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2 citations
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TL;DR: A procedure for simulating the antenna on commercial EM solvers and several strategies to modulate the output of antennae, which is crucial for them to be suitable for wireless communications, are introduced.
Abstract: Interdigitated photomixing antennas (PMA), are amongst the most common sources for future terahertz wireless communication systems. In this contribution, a novel and interesting design of a PMA employing graphene as its electrode material has been proposed. The use of graphene provides several potential advantages over conventional metallic electrodes. Variation of the PMA output as a function of various parameters have been discussed and a novel scheme for producing modulation in the PMA output, using an additional signal source, has been introduced. The multiphysical scenario in the functioning of the PMA has been elegantly analyzed with a generalized and simple model. Expressions for the radiated fields from the antenna have been derived using the proposed model and have been validated with full-wave simulations. This paper introduces a procedure for simulating the antenna on commercial EM solvers. Several strategies to modulate the output of antennae, which is crucial for them to be suitable for wireless communications, have also been proposed and discussed with several key findings. The role of some of the antenna parameters have also been investigated. The uniqueness of this analysis lies in its simplicity and generalization along with its capability to combine the multi-physical scenario in the operation of the PMA.
2 citations
References
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01 Dec 1967
TL;DR: In this article, the experimental dependence of carrier mobilities on doping density and field strength in silicon has been investigated and the curve-fitting procedures are described, which fit the experimental data.
Abstract: Equations are presented which fit the experimental dependence of carrier mobilities on doping density and field strength in silicon. The curve-fitting procedures are described.
1,445 citations
"Magnetic Field-Assisted Radiation E..." refers methods in this paper
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TL;DR: In this article, stand-off interferometric imaging and sensing for the detection of explosives, weapons and drugs is emphasized, and future prospects of terahertz technology are discussed.
Abstract: Over the past 5 years, there has been a significant interest in employing terahertz (THz) technology, spectroscopy and imaging for security applications. There are three prime motivations for this interest: (a) THz radiation can detect concealed weapons since many non-metallic, non-polar materials are transparent to THz radiation; (b) target compounds such as explosives and illicit drugs have characteristic THz spectra that can be used to identify these compounds and (c) THz radiation poses no health risk for scanning of people. In this paper, stand-off interferometric imaging and sensing for the detection of explosives, weapons and drugs is emphasized. Future prospects of THz technology are discussed.
1,410 citations
"Magnetic Field-Assisted Radiation E..." refers background in this paper
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TL;DR: In this article, the change in refractive index Delta n produced by injection of free carriers in InP, GaAs, and InGaAsP was theoretically estimated and the results were in reasonably good agreement with the limited experimental data available.
Abstract: The change in refractive index Delta n produced by injection of free carriers in InP, GaAs, and InGaAsP is theoretically estimated. Bandfilling (Burstein-Moss effect), bandgap shrinkage, and free-carrier absorption (plasma effect) are included. Carrier concentrations of 10/sup 16//cm/sup 3/ to 10/sup 19//cm/sup 3/ and photon energies of 0.8 to 2.0 eV are considered. Predictions for Delta n are in reasonably good agreement with the limited experimental data available. Refractive index changes as large as 10/sup -2/ are predicted for carrier concentrations of 10/sup 8//cm/sup 3/ suggested that low-loss optical phase modulators and switches using carrier injection are feasible in these materials. >
926 citations
"Magnetic Field-Assisted Radiation E..." refers background or methods in this paper
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TL;DR: A comprehensive review of the various techniques used for terahertz image formation can be found in this paper, as well as numerous examples which illustrate the many exciting potential uses for these emerging technologies.
Abstract: Within the last several years, the field of terahertz science and technology has changed dramatically. Many new advances in the technology for generation, manipulation, and detection of terahertz radiation have revolutionized the field. Much of this interest has been inspired by the promise of valuable new applications for terahertz imaging and sensing. Among a long list of proposed uses, one finds compelling needs such as security screening and quality control, as well as whimsical notions such as counting the almonds in a bar of chocolate. This list has grown in parallel with the development of new technologies and new paradigms for imaging and sensing. Many of these proposed applications exploit the unique capabilities of terahertz radiation to penetrate common packaging materials and provide spectroscopic information about the materials within. Several of the techniques used for terahertz imaging have been borrowed from other, more well established fields such as x-ray computed tomography and synthetic aperture radar. Others have been developed exclusively for the terahertz field, and have no analogies in other portions of the spectrum. This review provides a comprehensive description of the various techniques which have been employed for terahertz image formation, as well as discussing numerous examples which illustrate the many exciting potential uses for these emerging technologies.
890 citations
"Magnetic Field-Assisted Radiation E..." refers background in this paper
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TL;DR: In this paper, an analytical expression for the electron and hole mobility in silicon based on both experimental data and modified Brooks-Herring theory of mobility was derived, which allows one to obtain electron and holes mobility as a function of concentration up to \sim 10^{20} cm-3 in an extended and continuous temperature range (250-500 K) within ± 13 percent of the reported experimental values.
Abstract: An analytical expression has been derived for the electron and hole mobility in silicon based on both experimental data and modified Brooks-Herring theory of mobility. The resulting expression allows one to obtain electron and hole mobility as a function of concentration up to \sim 10^{20} cm-3in an extended and continuous temperature range (250-500 K) within ± 13 percent of the reported experimental values.
824 citations
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