Mrinmoy Bharadwaj

Time dependent capacitance in Photoconductive Antenna

Photoconductive Antenna(PCA) is considered to be very simple and compact Terahertz (THz) generation source based on opto-electrical conversion method. In recent years, several experimental and simulation studies have been performed to analyze a PCA behavior. However, an accurate equivalent electrical circuit model is needed for theoretical analysis of a PCA. As the electrode gap region of PCA can be modeled as a charged capacitor, this work deals with the calculation of time dependent capacitance of a pulsed PCA system. The analysis of time dependent capacitance provides a better understanding of carrier dynamics in PCA and also helps in creating an accurate equivalent electrical circuit of PCA.

Effect of near fields on radiation from photoconductive antenna

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.

Equivalent electrical circuit model of Terahertz photoconductive antenna receiver in a pulsed system

Photoconductive antenna (PCA), due to its simple and compact structure, is emerging in recent times as a popular device for generation of Terahertz (THz) frequencies. The working of PCA is based on the optical-to-electrical power conversion technique. The main advantage of the PCA is that it can be used both as a source as well as a detector with little changes in the operating mechanism. In literature, several experimental, simulation and theoretical studied are available for PCA operating as a source. However, very few experimental and simulation studies are available to analyze the performance of PCA as a receiver. In this communication, an effort has been made to analyze the performance of a PCA as a receiver by modeling an equivalent electrical circuit of it, which is based on the physics involved in its operation.

Switched beam antenna system design at millimeter wave band employing graphene

In the present work we propose a novel 2-element RF level switched beam antenna array system realized through the application of Graphene. The proposed antenna system is designed to operate at 30 GHz. In this design, using Graphene, we try to realize an enhanced Butler matrix based switch beam antenna where the beam switching can be controlled through applied DC voltages. The various issues related to design of such antennas are investigated. The proposed antenna system may find applications in emerging 5G millimeter wave communication and also in wireless sensor networks.

Design of novel beam-switching semicircular microstrip antenna and transmission line with Graphene at Terahertz frequencies

A novel beam-switching printed semicircular antenna design has been proposed to operate at the Terahertz (THz) frequency band. The distinctive feature of the design lies in the use of Graphene to control the radiation characteristics of the antenna. Further, we extend the same idea to explore the applicability of Graphene for isolation of electromagnetic energy with the help of a simple design of a microstrip transmission line with Graphene. The proposed antenna and microstrip line designs have been carried out with an objective of realizing voltage controlled antennas and transmission lines which have lot of potential in various emerging and next generation wireless communication systems such as phased arrays, MIMO systems, sensor networks, etc.

A parametric study of photo carrier generation in Photoconductive Antenna

Photoconductive Antenna (PCA) is considered to be simple and compact source for the terahertz (THz) generation. PCA is a common device to generate THz signals. It uses optical-to-electrical conversion to generate the THz radiation. However, the major problem with PCA is the lower efficiency, which is below 1%. The efficiency of PCA systems depends on the current pulse generated by the photo-carriers through the ultrashort laser pulse excitation. In PCA, high efficiency can be achieved by generating a high amplitude current pulse. In this communication a 2D simulation study of current pulse formation is analyzed in the PCA. Also, the effect of different parameters such as input laser power, applied DC bias voltage, antenna and semiconductor material on current pulse generation has been studied to understand the behavior of PCA. The aim of this communication is to analyze the effect of different parameters at low laser power where the screening effect can be neglected. This work is expected to provide better understanding of the mechanism of THz generation and in deciding optimum parameters for maximizing Optical-to-THz conversion efficiency of PCA.