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 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.

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.

We present an efficient and compact laser pulse-pumped terahertz (THz) source suitable for on-chip applications. The THz emitter itself consists of a W(1.8 nm)/Fe(2 nm)/Pt(1.8 nm) metallic trilayer deposited via DC magnetron sputtering. Waveguides and a horn antenna are 3D-printed via 3D lithography and integrated with the emitter, resulting in a 19.6 dB increase in the measured THz power emitted at the design frequency of 1.5 THz.

We investigate the effect of surface oxide contamination on the terahertz (THz) emission via the inverse spin Hall effect from spintronic Fe/Pt bilayers pumped using femtosecond laser pulses. The metallic films were grown on Si and quartz substrates, both with and without a 300 nm Al2O3 spacer layer. The presence of the Al2O3 layer between the substrate and the metallic films results in a 350% increase in the measured THz electric field in the case of Si substrates, while an increase of 10% is observed when using quartz substrates. X-ray photoelectron spectroscopy (XPS) is used to gain insight into the elemental composition of the emitters, and the presence and intensity of iron oxide peaks explains the difference in the emitted THz signals.

In Beyond 5G wireless communication, the radio-over-fiber (RoF) technology that transmits signal waveforms of terahertz waves (0.1-10 THz) using optical fibers will be important. To realize such technology, it is required to develop a device that converts a terahertz signal into an optical signal. Organic electro-optic (EO) polymers can have large EO coefficients (> ~100 pm/V) and realize ultra-high-speed optical modulation of several hundred GHz or more. In this research, we prototyped 150-GHz-band antenna-coupled optical modulators with EO polymer waveguides and patch antenna arrays using a transfer and bonding method of a poled EO polymer film.

Patient motion during medical imaging can create significant degradation of images acquired in a clinical setting. Even breathing induced patient motion often leads to blurred imagery compromising its resolution and diagnostic utility. External motion tracking (EMT) technologies are one current method of tracking patient motion, but the current EMTs use radiation that is reflected off clothing or fixed markers, thus tracking only the patient’s garments. Researchers at U. Mass Worcester’s Chan Medical School and U. Mass Lowell’s Biomedical Terahertz Technology Center are seeking novel EMTs that use a part of the electromagnetic spectrum where clothing is transparent, designated as the millimeter wavelength region. For this purpose, the U. Mass. Team has developed a 75 GHz continuous-wave stepped frequency radar with 8 GHz bandwidth to investigate the system as a source-receiver tracking technology.

This conference presentation, “A method based on complementary transmission and reflection measurements for extracting the optical properties of a thin film” was presented at the Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications XV conference at SPIE Photonics West 2022.

This conference presentation, “Plasmonic nanocavities for enhanced terahertz emission and detection” was presented at the Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications XV conference at SPIE Photonics West 2022.

Terahertz layer thickness measurements is one of the most promising fields of applications for terahertz technology. Measuring subwavelength layers in multilayer systems is most commonly achieved by applying retrieval algorithms. These algorithms are computational demanding, which makes it hard for the evaluation to keep up with the increasing speed of modern terahertz systems. ECOPS-based systems now achieve measurement rates above 1 kHz. By applying a highly efficient algorithm based on desktop-grade CPU, we achieve multilayer imaging at 1.6 kHz measurement rate. A three-layer system on a metal disk of 300 mm diameter is measured in 2.5 minutes with 240000 pixels.

PILOT (Polarized Instrument for Long wavelength Observations of the Tenuous interstellar medium) is a balloon-borne telescope designed to study the polarized emission of dust in the diffuse interstellar medium in our Galaxy. The PILOT experiment allows observations at 1.2 THz (240 µm) with an angular resolution of about two arc-minutes. Pilot optics is composed an off axis Gregorian type telescope and a refractive re-imager system. All optical elements are in a cryostat cooled to 2K except the primary mirror, which is at ambient temperature (the room temperature during the end-to-end ground test or the temperature at ceiling altitude of about 40 km in flight). All optics system is aligned at room temperature and we have developed a dedicated procedure in order to keep the tight requirements on the focus position and ensure the instrument performances in the different environments. We combined the optical, 3D dimensional measurement methods and thermo-eslastic modeling to perform the optical alignment.

We demonstrated frequency controlled terahertz wave generation based on parametric wavelength conversion in a nonlinear MgO:LiNbO3 crystal. The pumping beam is generated using a PPLN-OPG seeded by a stabilized laser beam as traceable to the national standard. The generated pulses are amplified by a KTA-OPA pumped by a SLM Nd:YAG MOPA system. The seeding beam is monitored and controlled by a “spectral drill” cavity. The frequency of seeding beam is observed as intensity error signal. We expect that these methods will open up new fields.