Effect of near fields on radiation from photoconductive antenna
01 May 2017-pp 140-142
TL;DR: In this paper, a theoretical analysis of the effect of the near fields on the radiated terahertz (THz) radiation from a large aperture photoconductive antennas (PCA) is presented.
Abstract: Photoconductive antennas (PCA) are becoming very popular sources for the generation of Terahertz (THz) radiation. Various studies have been reported in the literature to understand the different physics involved in the operation of PCA. However, the effect of the near fields on the radiated THz from PCA is not analyzed adequately. In this work, a theoretical calculation of the radiated near fields and their effect on the radiated fields from a large aperture PCA have been investigated. The carrier dynamics presented in this work include the effect of the near fields, interaction between electrons and holes and time-dependent development of polarization due to space charge.
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Proceedings Article•
12 May 1991TL;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
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.
9 citations
Cites background or methods from "Effect of near fields on radiation ..."
...Recently, the effect of the radiated near-zone fields on the radiated far-zone electric field from a large aperture PCA has been reported in [18]....
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...The values of the different parameters used in the calculations are based on [8], [18], [30], [34], [36], and [37] and given in Table I....
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...In this paper, with some modifications, the same carrier dynamics model as presented in [18] is used to calculate the behavior of different parameters....
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...The mobility and mass of the electrons and the holes have been inherited from [18]....
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...In [18], it has been shown that the radiated near-zone field exerts a negative effect on the net electric field at the electrodes gap, which reflects in the form of reduced current density in the PCA....
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References
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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.
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TL;DR: In this article, a simple model based on the Drude-Lorentz theory of carrier transport was proposed to account for the details of the ultrashort terahertz pulses radiated from small photoconductive semiconductor antennas.
Abstract: 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.
540 citations
TL;DR: In this article, the authors reviewed the most recent results in terahertz fields and focused on the physical principles of tera-hertz generators and receivers, underlining the link between terahethertz devices and modern technologies such as micromachining and nanotechnology.
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TL;DR: In this paper, an overview of the range of available terahertz sources, emphasizing recent developments, is given, and the focus then narrows to the sources that rely on surface phenomena.
Abstract: Bibliometric data set the scene by illustrating the growth of terahertz work and the present interest in terahertz science and technology. After locating terahertz sources within the broader context of terahertz systems, an overview is given of the range of available sources, emphasizing recent developments. The focus then narrows to terahertz sources that rely on surface phenomena. Three are highlighted. Optical rectification, usually thought of as a bulk process, may in addition exhibit a surface contribution, which, in some cases, predominates. Transient surface currents, for convenience often separated into drift and diffusion currents, are well understood according to Monte Carlo modelling. Finally, terahertz surface emission by mechanical means—in the absence of photoexcitation—is described.
352 citations