we propose a new generation of unbiased (bias-free) antenna-less cw thz photomixer emitters array made of asymmetric msm gratings with subwavelength pitch, operating in optical near-field regime. we take advantage of the size effects in near-field optics and electrostatics to demonstrate the possibility of enhancing the thz power by four orders of magnitude, as compared with a similar array of ...

Intense terahertz em itters are one of the most important components of terahertz (THz) time-domain spectroscopy systems. In this presented report, the development of THz emitters over the last two decades is reviewed, and an outlook for future THz emitters is given. The physical principle behind the THz generation process is discussed for two types of emitters: state-of-the-art large-area phot...

The saturation properties of terahertz emission from biased, large-aperture photoconductors excited by trains of amplified femtosecond optical pulses are presented. A direct comparison is made of the multiple-pulse saturation properties of terahertz emission from semi-insulating GaAs and low-temperature-grown GaAs emitters with different carrier lifetimes. When the carrier lifetime is less than...

We present a comprehensive analysis of terahertz radiation from large area plasmonic photoconductive emitters in relation with characteristics of device substrate. Specifically, we investigate the radiation properties of large area plasmonic photoconductive emitters fabricated on GaAs substrates that exhibit short carrier lifetimes through low-temperature substrate growth and through epitaxiall...

| It is shown that unipolar quantum well systems have potential as sources of terahertz radiation. It is demonstrated that the electronic interactions within these systems must be manipulated in order to favour radiative emission rather than non-radiative loss. Designs are advanced for tunable emitters and optically excited terahertz lasers.

Illuminated by ultrashort optical pulses, large area multiplex terahertz semiconductor emitters that work on photoDember currents and Schottky potentials radiate a directional electromagnetic terahertz pulse which is controlled by the angular spectrum of the incident optical beam. Using the lens that focuses the incident near infra-red pulse, we have demonstrated THz emission focusing in free s...

Even though the terahertz spectrum is well suited for chemical identification, material characterization, biological sensing and medical imaging, practical development of these applications has been hindered by attributes of existing terahertz optoelectronics. Here we demonstrate that the use of plasmonic contact electrodes can significantly mitigate the low-quantum efficiency performance of ph...

We report on the surprisingly strong, broadband emission of coherent terahertz pulses from ultrathin layers of semiconductors such as amorphous silicon, germanium and polycrystalline cuprous oxide deposited on gold, upon illumination with femtosecond laser pulses. The strength of the emission is surprising because the materials are considered to be bad (amorphous silicon and polycrystalline cup...

We present a polarization-insensitive plasmonic photoconductive terahertz emitter that uses a two-dimensional array of nanoscale cross-shaped apertures as the plasmonic contact electrodes. The geometry of the cross-shaped apertures is set to maximize optical pump absorption in close proximity to the contact electrodes. The two-dimensional symmetry of the cross-shaped apertures offers a polariza...

Photoconductive (PC) terahertz (THz) emitters are often limited by ohmic loss and Joule heating-as these effects can lead to thermal runaway and premature device breakdown. To address this, the proposed work introduces PC THz emitters based on textured InP materials. The enhanced surface recombination and decreased charge-carrier lifetimes of the textured InP materials reduce residual photocurr...