We demonstrated simple terahertz applications using a coherent homodyne continuous-wave (CW) terahertz (THz) system. The system was developed based on a compact semiconductor dual-mode laser diode (DML). The DML was used for an optical beat source to generate a THz CW. The two lasing modes from the DML are well correlated and generate a high-purity THz CW signal. The system was applied to measu...

Near-field imaging with terahertz (THz) waves is emerging as a powerful technique for fundamental research in photonics and across physical and life sciences. Spatial resolution beyond the diffraction limit can be achieved by collecting THz waves from an object through a small aperture placed in the near-field. However, light transmission through a sub-wavelength size aperture is fundamentally ...

The transient absorption bleaching and velocity overshoot of photoexcited carriers in GaAs and Si have been observed by the intense few-circle terahertz (THz) probe pulse in the optical pump-terahertz probe (OPTP) configuration. The free-carrier THz nonlinearity is attributed to the transient electron redistribution in conduction band induced by the strong THz electric field component.

Planar metasurface based quarter-wave plates offer various advantages over conventional waveplates in terms of compactness, flexibility and simple fabrication; however they offer very narrow bandwidth of operation. Here, we demonstrate a planar terahertz (THz) metasurface capable of linear to circular polarization conversion and vice versa in a wide frequency range. The proposed metasurface is ...

We numerically investigate terahertz (THz) pulse generation by linearly-polarized, two-color femtosecond laser pulses in highly-ionized argon. Major processes consist of tunneling photoionization and ponderomotive forces associated with transverse and longitudinal field excitations. By means of two-dimensional particle-in-cell (PIC) simulations, we reveal the importance of photocurrent mechanis...

Recently, there has been increasing interest in object imaging and detection behind obscuring layers because of applications in detection of improvised explosive devices (IEDs) and suspicious materials. Millimeter (MMW) and terahertz waves show promise in detecting and imaging objects through clothing or packaging materials. In this paper, we discuss an electromagnetic model based on a multi-la...

The birefringence of LiInS2 (LIS) crystals in the THz frequency region is investigated by THz time-domain spectroscopy (THz-TDS). The experimental results indicate that LIS has large birefringence and low absorption in the THz frequency region. The optical properties of LIS are quantitatively determined. A sharp absorption caused by a TO-phonon resonance is observed at around 1.70 THz when the ...

In order for the promise of terahertz (THz) wireless communications to become a reality, many new devices need to be developed, such as those for routing THz waves. We demonstrate a power splitting router based on a parallel-plate waveguide (PPWG) T-junction excited by the TE1 waveguide mode. By integrating a small triangular septum into the waveguide plate, we are able to direct the THz light ...

Terahertz (THz) radiation, often referred to the frequency range from 0.1 to 10 THz, is the focus of an active and fast growing research community. However, this frequency range located in the electromagnetic spectrum between the microwave band and infrared band, was known as the “THz-gap” until the late 1980's. A lack of available coherent sources and detectors rendered this frequency range in...

Emission of terahertz (THz) electromagnetic (EM) waves from a high critical temperature (Tc) superconductor intrinsic Josephson junction (IJJ) is a new and promising candidate for practical applications of superconducting devices. From the engineering viewpoint, the IJJ THz source is competitive against the present semiconducting THz sources such as quantum cascade lasers (QCLs) and resonance t...