In this paper, we present our experimental results on the electrically pumped optoelectronic mixing effect exhibited
in a niobium nitride (NbN) superconducting nanowire. The experimental setup in order to test the mixer
has been reported in detail. This superconductive nanowire optoelectronic mixer demonstrates photodetection
and mixing in an integrated manner. We have explored both effects under a great variety of external conditions,
such as temperature and bias current, in order to seek potential ways toward quantum optoelectronic detection
and mixing by such nanowire device.
This paper studies the role of plasmonic modes for guided-wave propagation of THz/far infrared in metalclad
planar waveguides, including metal-dielectric interfaces, dielectric-loaded metal slabs and parallel plate
waveguides. The dispersion of modal characteristics of the plasmonic guided waves, such as the effective index,
attenuation constant and the field confinement, as a function of geometrical features for different consisting
materials and wavelengths are examined. Moreover, comparison is made between the THz plasmonic modes to
their optical counterparts at visible/near infrared within the similar physical structures. Peculiar features of
each structure are highlighted and regimes of interest are distinguished.
This paper investigates the use of plasmonic optical waveguides in superconductive traveling-wave photodetectors
(STWPDs) as a promising technique to efficiently couple the input optical field into the superconducting detecting
structures. Field analysis is employed to study the propagation of the light through the integrated device and
the coupling of optical power from the plasmonic waveguide to the superconducting film as a function of physical
dimensions of the guide. A sample plasmonic waveguide, based on the LaAlO3-YBCO-Au multilayer, will be
discussed in detail and important design rules are addressed.
The ultrafast and sensitive detection of an optical beat signal generated from an optical heterodyne system in
an integrated traveling-wave photoconductive detector with high-temperature superconducting (HTS) coplanar
electrode lines has been introduced for generating THz signals.While the optical beat signal has been absorbed
by photoconductive substrate and an HTS center strip, the THz signal is gradually bulit up on the HTS coplanar
waveguide (CPW). The kinetic inductive photoresponse of the HTS strip contributes excessively in the generation
of multi-THz signal while the response of the photoconductor substrate decreases with increasing THz frequency.
A rigorous optical analysis of a multilayer waveguide in conjunction of optical-to-THz signal conversion analysis
have been carried out to find the external conversion effciency of such a photodetector. Our simulation shows
that the GaAs-based structure with YBCO electrode at1.5 μm exhibits more output THz power than its Si
counterpart in 850 nm wavelength.
The concept of a traveling-wave photodector based on the integration of semiconductor substrate with high-temperature superconducting (HTS) slabs is proposed for the first time. The photoconductivity effect in semiconducting substrate and the kinetic inductive photoresponse in HTS slabs has been used to obtain a sensitive and broadband optical detection with a large responsivity over a very wide range of electrical frequency spectrum. The analysis of optical wave propagation down the photodetector waveguide is presented in detail by introducing a transcendental equation for optical propagation constant. The photomixing technique is used to excite the photodetector waveguide and the output photo-induced electrical signal is analyzed by means of transmission line theory in frequency domain. The presented analytical and numerical studies of such a photodetector waveguide reveals many interesting device characteristics including high responsivity for high beat electrical frequencies and the possibility of high-power mm-wave signal generation in such a structure.
Continues-wave photomixing phenomenon in ultra-fast photoconductors
and high-temperature superconductors (HTS) is studied and photomixing efficiencies of these materials are investigated.
Photocurrent distributions in both photoconductor and superconductor
based photomixers are calculated and their common characteristics
are compared in detail.
A new CW photoconductive integrated photomixer/antenna THz source is presented. A THz signal is generated in the DC-biased photoconductive strip by employing optical heterodyne photomixing, and at the same time the size of the photoconductive strip on the grounded dielectric substrate is designed to have an efficient broadside radiation. Analytical expressions for the photo-induced current as well as the radiation power are calculated in detail, which make it possible to evaluate the performance of the structure made by different photoconductive materials. The typical μW output power can be obtained by mW laser pump power for frequencies up to 1 THz.
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