Terahertz Frequency Multiplier Research Articles

On‐Demand Generation and Control of Giant Terahertz Nonlinearity with Metasurfaces

AbstractSimultaneous control of the optical linearity and nonlinearity of the materials plays key roles in next‐generation electronics and optics as it offers the potential of manipulating the fundamental properties while generating new frequencies of light. Such control is exceedingly challenging at the technologically important terahertz (THz) frequencies due to the severe scarcity of high‐performance nonlinear materials. Here, a unique method is introduced for achieving THz second‐order nonlinearity through Lorentz force‐driven anharmonic oscillations of free electrons in metasurfaces. It does not depend on natural nonlinear materials and provides ultrahigh design freedom. Using this approach, efficient THz second harmonic generation (SHG) is experimentally demonstrated with remarkably large values of the effective nonlinear susceptibility at room temperature. By engineering the geometry of the metasurfaces, the generation and suppression of the second harmonics can be controlled and customize their polarization states at will. This efficient, configurable, room‐temperature, and ultra‐compact platform for THz SHG provides new perspectives for developing high‐performance THz sources, frequency multipliers, and other nonlinear devices.

Thermal Analysis of THz Schottky Diode Chips with Single and Double-Row Anode Arrangement.

GaN Schottky diodes show great potential in high-power terahertz frequency multipliers. The thermal characteristics of GaN Schottky diodes with single and double-row anode arrangements are described in this paper. The temperature distribution inside the Schottky diode is discussed in detail under the coupling condition of Joule heat and solid heat transfer. The effects of different substrates and substrate geometric parameters on the thermal characteristics of the Schottky diode chips with single and double-row anode arrangements are systematically analyzed. Compared with that of the chip with single-row anode arrangement, the maximum temperature of the chip with double-row anode arrangement can be reduced by 40 K at the same conditions. For chips with different substrates, chips with diamond substrates can withstand greater power dissipation when reaching the same temperature. The simulation results are instructive for the design and optimization of Schottky diodes in the terahertz field.

The Development of Frequency Multipliers for Terahertz Remote Sensing System

This paper summarizes the development of novel Schottky-diode-based terahertz frequency multipliers. The basic structure and manufacturing process of planar Schottky barrier diodes (SBDs) are reviewed, along with other diode structures that have been proposed in the literature. A numerical modeling method for the novel diodes in the context of terahertz frequency multipliers is presented, which includes 3D electromagnetic (EM) modeling, electro-thermal modeling and modeling of physical non-ideal effects. Furthermore, a general design methodology for developing terahertz frequency multipliers is introduced, involving a sub-division design method (SDM), a global design method (GDM) and a half-sub-division and half-global design method (HS-HGDM). These methods are summarized and compared for 110 GHz and 220 GHz frequency multipliers in the context of communication and imaging applications. Laboratory measurements of these multipliers show good agreement with numerical simulations. Finally, several classic terahertz remote sensing systems are reviewed, and a 220 GHz remote sensing system established using novel frequency multipliers for security inspection purposes is presented along with associated imaging results.

Theoretical Analysis of Terahertz Frequency Multiplier Based on Semiconductor Superlattices.

We propose a terahertz frequency multiplier based on high order harmonic generation in a GaAs-based miniband superlattice driven by an electric field. The performance of the frequency multiplier is analyzed using the balance equation approach, which incorporates momentum and energy relaxation processes at different lattice temperatures. It is found that the generated high-order harmonic power is sensitive to temperature changes. The peak power appears around resonance between driving terahertz frequency and intrinsic Bloch frequency. In the presence of the magnetic field, the peak power shifts towards a stronger static electric field region. The simulated results about the dependence of the second and third harmonic powers on a DC electric field are in qualitative consistence with the experiments. The proposed terahertz frequency multiplier based on semiconductor superlattice, being compact and efficient, is provided as a good candidate for terahertz wave generation.

A new approach to the development of perspective compact frequency multipliers of the subterahertz and terahertz bands for on-board electronic equipment

Currently, the increasing interest of researchers is attracted by the theoretical and practical problems of mastering the sub-terahertz and terahertz frequency range. Electronic devices operating in these ranges find effective applications in various fields of science and technology: aerospace equipment, security systems, spectroscopy, medicine, biology and many others. The purpose of this work is to focus on a frequency multiplication device that allows using basic sources of relatively low frequency generation to enter the terahertz frequency range. The results of recent years obtained both on the basis of solid-state effects and with the help of vacuum electronics, in particular, magnetron-type devices, which are characterized by compactness, high resistance to radiation loads, mechanical influences, which is important for on-board equipment, are considered. It is known that at high frequencies, vacuum devices require super-precision manufacturing of decelerating systems. This is essentially the main difficulty. The article proposes a new approach based on the hypothesis of P.L. Kapitsa, which allows to significantly simplify the anode structure of a magnetron multiplier with an acceptable level of output parameters. The achievements of recent years in the field of creating sub-terahertz and terahertz frequency multipliers, mainly for on-board equipment of mobile platforms, taking into account the requirements of aerospace systems, first of all, are noted.

Development of 340-GHz Transceiver Front End Based on GaAs Monolithic Integration Technology for THz Active Imaging Array

Frequency multipliers and mixers based on Schottky barrier diodes (SBDs) are widely used in terahertz (THz) imaging applications. However, they still face obstacles, such as poor performance consistency caused by discrete flip-chip diodes, as well as low efficiency and large receiving noise temperature. It is very hard to meet the requirement of multiple channels in THz imaging array. In order to solve this problem, 12-μm-thick gallium arsenide (GaAs) monolithic integrated technology was adopted. In the process, the diode chip shared the same GaAs substrate with the transmission line, and the diode’s pads were seamlessly connected to the transmission line without using silver glue. A three-dimensional (3D) electromagnetic (EM) model of the diode chip was established in Ansys High Frequency Structure Simulator (HFSS) to accurately characterize the parasitic parameters. Based on the model, by quantitatively analyzing the influence of the surface channel width and the diode anode junction area on the best efficiency, the final parameters and dimensions of the diode were further optimized and determined. Finally, three 0.34 THz triplers and subharmonic mixers (SHMs) were manufactured, assembled, and measured for demonstration, all of which comprised a waveguide housing, a GaAs circuit integrated with diodes, and other external connectors. Experimental results show that all the triplers and SHMs had great performance consistency. Typically, when the input power was 100 mW, the output power of the THz tripler was greater than 1 mW in the frequency range of 324 GHz to 352 GHz, and a peak efficiency of 6.8% was achieved at 338 GHz. The THz SHM exhibited quite a low double sideband (DSB) noise temperature of 900~1500 K and a DSB conversion loss of 6.9~9 dB over the frequency range of 325~352 GHz. It is indicated that the GaAs monolithic integrated process, diodes modeling, and circuits simulation method in this paper provide an effective way to design THz frequency multiplier and mixer circuits.

Self-Consistent Electro-Thermal Approach for Terahertz Frequency Multiplier Design

Solid-state sources consisting of cascaded Schottky diode-based frequency multipliers are commonly used to generate power at millimeter and submillimeter wave bands. In order to achieve increasing power at those frequencies, first-stage frequency multipliers have to handle a large amount of input power and generate enough output power to drive higher frequency multiplication stages. To that end, an appropriate electro-thermal design of multiplier circuits can result in improvement of power-handling capabilities without degradation of conversion efficiency. This work proposes an approach for the design of frequency multipliers where both electrical and thermal considerations are self-consistently taken into account along the optimization of the Schottky diode structure and the circuit layout. The proposed methodology is validated with the design and test of a split-block waveguide single-chip tripler circuit with output frequency in the 225–325-GHz band. Good agreement between predicted performance and measured results is obtained for a wide input power range and different ambient temperatures.

A 600 GHz varactor frequency multiplier using 65-nm CMOS technology

A terahertz frequency multiplier is fabricated using a 65-nm CMOS technology. A modified model for an n-type thin-oxide varactor is also created from measured S-parameter data sets around 300 and 600 GHz. The multiplier circuit produces −20.9 dB m of probe-measured output power at 595 GHz, and its performance is in a close agreement with the simulated data proving the accuracy of the modified varactor model.

THz Diode Technology: Status, Prospects, and Applications

Found in many terahertz (THz) and submillimeter-wave systems, GaAs Schottky diodes continue to be one of the most useful THz devices. As a low-parasitic device that operates well into the THz range, Schottky diodes provide useful detection and power generation for a number of practical applications. Mixers and multipliers, working as high as ~3 THz, have already been demonstrated. This paper reviews the current status of diode technology, detailing some of the different ways for fabricating THz chips. An overview regarding the current state of technology and performance for THz frequency multipliers and mixers is presented, along with applications enabled by these diodes.

A 220 GHz frequency tripler based on 3D electromagnetic model of the schottky diode and the field-circuit co-simulation method

In this article, a 220 GHz frequency tripler using three-dimensional (3D) electromagnetic simulation is designed. Due to the characteristics of extremely short working wavelength and ultra-small circuit size of terahertz frequency multipliers, complicated parasitic effect cannot be ignored, which leads to a limited optimization space for circuit matching in the design of terahertz components. In this article, a precise 3D electromagnetic (EM) model of the planar Schottky barrier diode (SBD) is established and the field-circuit co-simulation method is proposed for the design of the 220 GHz tripler. Compared with the varistor diode, the frequency multiplier based on the varactor diode will produce higher output power due to its lossless mechanism. The measured results show that the output power is higher than 5 mW in the frequency range 220∼228 GHz, with the maximum output power of 6.34 mW. Typical conversion loss is 15 dB in the frequency range 216∼232 GHz. The frequency tripler has the characteristics of compact size, low loss, and high output power. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1647–1651, 2016

Schottky diode-based terahertz frequency multipliers and mixers

Abstract This article presents some aspects of the technology of terahertz heterodyne receiver front-ends dedicated to astrophysics, planetary and atmospheric sciences. It focuses on frequency multipliers and on Schottky mixers. Novel architectures of power-combined frequency multipliers at submillimeter-wavelengths, THz planar fundamental mixers, and integrated receivers will be discussed, as well as the fabrication of submillimeter-wave planar Schottky diodes in France.