In this study, we designed and fabricated GaAs AP-SBDs for a 300 GHz subharmonic mixer. To enhance the reliability of electromagnetic simulations, we measured and calculated the optical parameters of the material in the terahertz range and designed a component with minimal impedance variation across the frequency range of 140-300 GHz. GaAs AP-SBDs were fabricated using MOCVD and an i-line stepper, followed by electrical characterization. Finally, a subharmonic mixer was constructed using WR3.4/WR6.5 waveguides, achieving an single side band conversion loss of 9.72 dB and a 3 dB bandwidth of 40 GHz.
In this paper, we will demonstrate a photonics-based 300 GHz THz wireless communication with our new-type dual-mode laser(DML) beating light source which is directly modulated at a rate of more than10 Gbps. Also, we verified that using of the DML is superior in terms of stability and linewidth than other technique of photomixing using a two distributed-feedback(DFB) LDs.
The properties of terahertz (THz) radiation make it possible to inspect a variety of non-conductive materials, such as paper, plastic, cloth, etc., without causing damage to the human body. THz wave characteristics have been used in numerous studies on application systems for non-destructive and manufacturing process monitoring as a result.
In this presentation, we introduce how to set up a contactless thickness monitoring system with long-term signal stabilization of CW THz signals to achieve signal stabilization within 1% for 12 hours insensitive to changes in ambient temperature.
This conference presentation, “Waveguide packaged UTC-PD module for terahertz applications” was presented at the Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications XV conference at SPIE Photonics West 2022.
In this work, we reported the 1.55 ㎛ ridge-type dual mode laser(R-DML) as a THz communication beating source. It have many advantages of cost effects, compactness and simplification of fabrication by introducing the ridge-type waveguides. We have demonstrated 10Gbps THz wireless communications with 10-3 BER (bit-error-rate) without digital signal processing.
In this study, we report GaAs SBD-based subharmonic mixer for THz communication in the 220-330 GHz band. n GaAs:Si and n++ GaAs:Si were grown on semi-insulating GaAs substrate by using metal-organic chemical vapor deposition. Antiparallel(AP)-SBD was fabricated using the i-line stepper. The schottky junction, defined to be less than 1 um, has been composed of Ti/Pt/Au. The I-V and C-V characteristics of the fabricated AP-SBD were measured for the ideal factor, series resistance, current parameter, junction capacitance and parasitic capacitance. RF matching and LO and IF filters were designed with HFSS capable of 3D electromagnetic wave computational simulation. We also simulated the GaAs subharmonic mixer circuit using the nonlinear analysis of ADS. The conversion loss of the mixer module was measured and compared with the computational simulation results. Finally, we demonstrate the THz communication with 50 Gbps QPSK signal in the 300 GHz band.
In developing terahertz (THz) technologies that are more suitable for industrial applications, we have focused on research on continuous-wave (CW) THz technologies to develop small, low-cost, and multifunctional THz devices and systems. In the course of this research, we have developed several key devices such as widely tunable compact beating sources in the form of dual mode lasers, THz emitters, including nano-electrode-photomixers and uni-traveling carrier photodiode photomixers, and highly sensitive THz detectors, such as Schottky barrier diodes (SBDs). In this study, along with our recently obtained results that demonstrate the enhanced performance of these devices, we also present an example of a practical industrial application of our CW THz system: a nondestructive evaluation (NDE) system. The system described can be applied in the car manufacturing factory as an NDE technique to find process errors. Although further improvements to photonics-based THz technologies are necessary, we believe that efforts in this field will begin an era of THz technologies as a widely-used industrial technique.
Recently, a wide interest has been gathered in using terahertz (THz) waves as the carrier waves for the next generation of broadband wireless communications. Upon this objective, the photonics technologies are very attractive for their usefulness in signal generations, modulations and detections with enhanced bandwidth and data rates, and the readiness in combining to the existing fiber-optic or wireless networks. In this paper, as a preliminary step toward the THz wireless communications, a THz wireless interconnection system with a broadband antenna-integrated uni-traveling-carrier photodiode (UTC-PD) and a Shottky-barrier diode (SBD) module will be presented. In our system, optical beating signals are generated and digitally modulated by the optical intensity modulator driven by a pulse pattern generator (PPG). As the receiver a SBD and an IF filter followed by a low-noise preamplifier and a limiting amplifier was used. With a 6-mA photocurrent of the UTC-PD which corresponds to the transmitter output power of about 30 μW at 280 GHz, an error-free (BER<10-9) transmission has been achieved at 2.5 Gbit/s which is limited by a limiting amplifier. With this system, a 1.485-Gbit/s video signal with a high-definition serial digital interface format was successfully transmitted over a wireless link.
Terahertz (THz) waves have been actively studied for the applications of astronomy, communications, analytical science and bio-technologies due to their low energy and high frequency. For example, THz systems can carry more information with faster rates than GHz systems. Besides, THz waves can be applied to imaging, sensing, and spectroscopy. Furthermore, THz waves can be used for non-destructive and non-harmful tomography of living objects. In this reasons, Schottky barrier diodes (SBD) have been widely used as a THz detector for their ultrafast carrier transport, high responsivity, high sensitivity, and excellent noise equivalent power. Furthermore, SBD detectors envisage developing THz applications at low cost, excellent capability, and high yield. Since the major concerns in the THz detectors for THz imaging systems are the realizations of the real-time image acquisitions via a reduced acquisition time, rather than the conventional raster scans that obtains an image by pixel-by-pixel acquisitions, a line-scan based systems utilizes an array detector with an 1 × n SBD array is preferable.
In this study, we fabricated the InGaAs based SBD array detectors with broadband antennas of log-spiral and square-spiral patterns. To optimize leakage current and ideality factor, the dependence to the doping levels of ohmic and Schottky layers have been investigated. In addition, the dependence to the capacitance and resistance to anode size are also examined as well. As a consequence, the real-time THz imaging with our InGaAs SBD array detector have been successfully obtained.
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