Plasmonics enhanced photomixing for generating quasi-continuous-wave frequency-tunable terahertz radiation

Abstract

We experimentally demonstrate an order of magnitude enhancement in the quasi-continuous-wave radiated power from a photomixer with plasmonic contact electrodes in comparison with an analogous conventional photomixer without plasmonic contact electrodes in the 0.25-2.5 THz frequency range when pumped at an optical wavelength of 1550 nm. The significant efficiency enhancement results from the unique capability of the plasmonic contact electrodes to reduce the average transport path of photocarriers to the device contact electrodes, increasing the ultrafast photocurrent that drives the terahertz antenna.

Enhancement of terahertz photoconductive antenna operation by optical nanoantennas

“…(a) shows the simplest layout for submillimetre waves generation in semiconductor (LT‐GaAs) based photoconductive antennas. Fs‐laser (usually Ti:Sapphire or much cheaper fiber‐based laser systems such as second or fundamental harmonic of Er‐doped fiber lasers) serves as a source of ultrashort light pulses with a duration of several tens or hundreds of femtoseconds. The shape of the optical pulse envelope is very important as it induces the nonlinear polarization of the same form (optical rectification), which is capable of increasing the output power of THz radiation .…”

Growth and properties of rare-earth arsenide InGaAs nanocomposites for terahertz generation

“…Development of fast photoconductive materials with smaller bandgaps, such as In 0.53 Ga 0.47 As, would benefit greatly from the mature telecommunication component infrastructure available at 1550 nm. 21 Unfortunately, previous investigations of devices with small bandgap materials, such as InP-based nipnip 22,23 and unitraveling carrier 24,25 diodes, plasmonic enhancements, 26,27 and mixers with promising materials such as LTG-InGaAs 28 and LTG-InGaAs/AlGaAs multilayer heterostructures, 29 have also yielded output powers that remain in the microwatt range at THz frequencies. InGaAs nanocomposite materials based on ErAs nanoparticle superlattice 30,31 and codeposited 32 structures, as well as TbAs codeposited structures, 33 have also been investigated, but currently possess prohibitively low dark resistivities.…”

Compact terahertz radiation source using a bimodal laser and plasmonic photomixer

“…1 We used a plasmonic photomixer to convert the optical beam from the two-section D-DFB laser to terahertz radiation. 5,6 The photomixer comprises an ultrafast photoconductor, with plasmonic contact electrode gratings, integrated with a logarithmic spiral antenna on an erbium arsenide:indium gallium arsenide substrate, as shown in Figure 2(a). When the optical beam from the two-section D-DFB laser is incident on the anode plasmonic contact electrodes, a large fraction of the photogenerated carriers is generated in close proximity to the contact electrodes (as a result of the excitation of surface plasmon waves).…”

“…By concentrating a major portion of the incident optical beam near the plasmonic contact electrodes, a large number of the photogenerated electrons drift to the anode plasmonic contact electrodes on a sub-picosecond timescale to efficiently contribute to terahertz radiation. [5][6][7][8][9][10][11] We then feed the induced photocurrent to the logarithmic spiral antenna to generate terahertz radiation at the beating frequency of the two main spectral peaks of the two-section D-DFB laser. We use a fiber amplifier with a 2% duty cycle to amplify the laser output before coupling it to the plasmonic photomixer.…”