Terahertz quantum cascade laser sources based on intra-cavity frequency mixing are currently the only monolithic electrically pumped semiconductor devices that can operate in the 1–6 THz spectral range at room temperature. The introduction of the Cherenkov waveguide scheme in these devices grown on semi-insulating InP substrates enabled generation of tens of microwatts of average terahertz powe...

We review recent progress in the field of terahertz “T-ray” imaging. This relatively new imaging technique, based on terahertz time-domain spectroscopy, has the potential to be the first portable far-infrared imaging spectrometer. We give several examples which illustrate the possible applications of this technology, using both the amplitude and phase information contained in the THz waveforms....

A plasmon-induced polarization conversion (PIPC) structure based on periodically patterned graphene was demonstrated in the THz regime. By varying the Fermi level of two connected T-shape graphene strips through the electrostatic gating, the peak frequency and the group index in the transparency window can be tuned, which is good agreement with the coupled Lorentz oscillator model. Due to inter...

We demonstrate efficient terahertz (THz) modulation by coupling graphene strongly with a broadband THz metasurface device. This THz metasurface, made of periodic gold slit arrays, shows near unity broadband transmission, which arises from coherent radiation of the enhanced local-field in the slits. Utilizing graphene as an active load with tunable conductivity, we can significantly modify the l...

THz wave has been increasingly applied in engineering practice. One of its outstanding advantages is the penetrability through certain optically opaque materials, whose interior properties could be therefore obtained. In this report, we develop an experimental method to determine the plane stress state of optically opaque materials based on the stress-optical law using terahertz time-domain spe...

We investigate high-power terahertz (THz) generation in two-color laser filamentation using terawatt (TW) lasers including a 0.5 TW, 1 kHz system, as well as 2 and 30 TW systems both operating at 10Hz. With these lasers, we study the macroscopic effect in filamentation that governs THz output energy yields and radiation profiles in the far field. We also characterize the radiation spectra at a ...

As short range, ground based, surveillance systems operating at terahertz frequencies continue to evolve, increasing attention is being directed towards the behavior of dielectric materials at terahertz frequencies as well as the behavior of optical components used to control terahertz radiation. This work provides an overview of several terahertz optical components such as frequency selective ...

A system for coupling teraherz (THz) radiation to a coaxial waveguide comprises an antenna that generates THz radiation having a mode that matches the mode of the waveguide. The antenna may comprise a pair of concentric electrodes, at least one of which may be affixed to or formed by one end of the waveguide. The radiation may have wavelengths between approximately 30 μm and 3 mm. The waveguide...

A compact, high power, room temperature continuous wave terahertz source emitting in a wide frequency range (ν~1-5 THz) is of great importance to terahertz system development for applications in spectroscopy, communication, sensing, and imaging. Here, we present a strong-coupled strain-balanced quantum cascade laser design for efficient THz generation based on intracavity difference frequency g...

Measurements of optical constants at terahertz—or T-ray—frequencies have been performed extensively using terahertz time-domain spectroscopy (THz-TDS). Spectrometers, together with physical models explaining the interaction between a sample and T-ray radiation, are progressively being developed. Nevertheless, measurement errors in the optical constants, so far, have not been systematically anal...