Shihab Al-Daffaie

Eindhoven University of Technology | TUE · Terahertz Nanophotonics and Integration Technology (TNIT)

This work proposes a new type of continuous-wave (CW) terahertz (THz) generation based on vertically integrated LTG-GaAs photomixer and Nanogrid-based transparent top bias-electrode. The THz output power can be increased by higher available photocurrents and smaller device capacitances. A suitable resonant antenna design is proposed.

New types of continuous-wave (CW) terahertz (THz) photomixers were fabricated using 1-D and 2-D nanocontacts on low-temperature-grown (LTG) GaAs as well as nitrogenion-implanted (N+i) GaAs. The 1D and 2-D nanocontacts were formed by silver nanowires and graphene sheets, respectively. A silver nanowire (Ag-NW) with a physical diameter of 60 nm and 1...

The specific nature of terahertz radiation creates a broad and important range of applications using this regime in the fields of astrophysics, plasma technology, material science, biomedical engineering, environmental science, information processing, spectroscopy, and imaging technology. Among many available terahertz sources, the photomixer is pr...

Some 50 years ago discussions of plasmonics in semiconductors lead to many new concepts such as travelling domain structures with applications leading even to logic systems. Now plasmonics of submicron wires of Ag and graphene bring new device concepts for the fabrication of compact THz sources and optical focusing of the beat signal into the activ...

A new integrated lens-antenna is designed and implemented for a nanocontact based terahertz (THz) photomixer. The new design replaces the standard conventional bulky silicon lens, which normally no THz photomixer can avoid. The Fresnel Zone Plate is used to design the new lens-antenna and is simulated by the MIT open-source tool called Meep. The fi...

Symmetry‐protected bound states in the continuum (BICs), emerging at the Γ0$\left(\Gamma\right)_{0}$ point in the Brillouin zone of periodic lattices of scatters, are robust optical modes under modifications in the lattice if the C2 symmetry (two fold rotational symmetry) is preserved. In this study, the manipulation of these symmetry‐protected BIC...

Designing terahertz sensors for highly sensitive detection of nanoscale thin films and a few biomolecules poses a substantial challenge but is crucial for unlocking their full potential in scientific research and advanced applications. This work presents a strategy for optimizing metamaterial sensors in detecting small quantities of dielectric mate...

Graphene has recently been shown to exhibit ultrafast conductivity modulation due to periodic carrier heating by either terahertz (THz) waves, leading to self-induced harmonic generation, or the intensity beat-note of two-color optical radiation. We exploit the latter to realize an optoelectronic photomixer for coherent, continuous-wave THz detecti...

Antenna-coupled photomixers, serving as emitters and receivers of terahertz (THz) radiation, are the central active components of coherent optoelectronic THz systems. Here, we focus on the continuous-wave modality, which finds ample use for spectroscopy, sensing, and ranging and plays a major role in upcoming ultrahigh-frequency telecommunication a...

Continuous-wave terahertz emitters based on photomixers with hybrid nanoelectrodes are investigated. The nanoelectrodes consist of a nitrogen-doped single layer of graphene and silver nanowires, placed on low-temperature-grown (LTG) GaAs as photoconductive material. Due to the high transparency of graphene and the low fill factor of nanowire nanoel...

Surface plasmon polaritons on (silver) nanowires are promising components for future photonic technologies. Here, we study near-field patterns on silver nanowires with a scattering-type scanning near-field optical microscope that enables the direct mapping of surface waves. We analyze the spatial pattern of the plasmon signatures for different exci...

ACS Omega 2019, 4, 26, 21962-21966 https://doi.org/10.1021/acsomega.9b03036 Surface plasmon polaritons on (silver) nanowires are promising components for future photonic technologies. Here, we study near-field patterns on silver nanowires with a scattering-type scanning near-field optical microscope that enables the direct mapping of surface wave...

A new type photomixer for continuous wave (CW) terahertz (THz) generation was fabricated using 6-8 layer graphene. The multilayer graphene (MLG) sheets were used as six-finger interdigital nanoelectrodes on a low-temperature-grown (LTG) GaAs photoconductor. The MLG nanoelectrode shows unique properties with high short-circuit current capabilities a...

In the past decade the InGaN/GaN-based light-emitting diodes (LEDs) have attracted attention of most researchers as a promising candidate to replace conventional lamps in lighting applications, including general illuminations, LCD display backlighting, and automobile lighting. However, the efficiency of LEDs is significantly reduced at high current...

We report on a new design of room-temperature terahertz quantum cascade lasers (THz QCLs) based on ZnMgSe/ZnSe material systems employing two-well design schemes with alternating quantum barrier heights and n-type delta-doping of the injector well. Our calculations show that this new THz QCLs achieves high optical gain at the emission frequency of...

A new type of continuous-wave (CW) terahertz (THz) photomixer was fabricated using a nitrogen-doped single layer graphene (N+SLG) powder and silver nanowire (Ag-NW of Ø 300 nm) on low-temperature-grown (LTG) GaAs. The new hybrid (N+SLG/Ag-NW) structure provides simple fabrication steps and better performance in terms of high current handling togeth...

II-VI compounds are promising materials for the fabrication of room-temperature terahertz devices due to their beneficial properties like as type-I conduction band alignment, high breakdown field strength (~331 kV/cm for ZnSe vs. ~80 kV/cm for GaAs), and higher values of the conduction band offset (1.5 eV for BeSe/ZnSe vs. 0.7 eV for AlAs/GaAs). In...

II-VI compounds are promising materials for the fabrication of room-temperature terahertz devices due to their beneficial properties like as type-I conduction band alignment, high breakdown field strength (~331 kV/cm for ZnSe vs. ~80 kV/cm for GaAs), and higher values of the conduction band offset (1.5 eV for BeSe/ZnSe vs. 0.7 eV for AlAs/GaAs). In...

Blue InGaN/GaN light-emitting diodes with undoped, heavily Si-doped, Si delta-doped, heavily Mg-doped, Mg delta-doped, and Mg–Si pin-doped GaN barrier are investigated numerically. The simulation results demonstrate that the Mg–Si pin-doping in the GaN barrier effectively reduces the polarization-induced electric field between the InGaN well and th...

Continuous-wave (CW) terahertz (THz) photomixers are fabricated using 1-D nanocontacts on low-temperaturegrown (LTG) GaAs and InGaAs, for operation wavelengths of 850nm and 1550 nm, respectively. Silver (Ag) nanowire (NW) is used as the nanocontact which is aligned between the antennas patterned onto these photomixers by dielectrophoresis (DEP) tec...

We present new kind of terahertz (THz) Schottky detectors based on high-doped GaAs and AlGaAs/GaAs high electron mobility transistor (HEMT) structure using silver (Ag) metallic nanowires (NWs) with different diameters as air-bridge contact between the antenna and Schottky anode. The dielectrophoresis allows a simple alignment of the NWs and fabrica...

In the past decade the AlInGaN-based light-emitting diodes (LEDs) have attracted attentions of most researchers as promising candidates to replace conventional lamps in lighting applications, including general illuminations, LCD display backlighting, and automobile lighting. However, the efficiency of LEDs is significantly reduced at higher current...

First various graphene realizations of electronic circuitry examples are described. These represent application examples for the new material graphene. Then compact THz sources are presented involving optical laser mixing, where resonant plasmonic structures at THz and optical frequencies are used to locally enhance the electromag-netic fields. Of...

A new type of a fully integrated vertical nanocontact THz photomixer was fabricated on LTG-GaAs / n+GaAs / SI-GaAs wafer with a single silver nanowire of Ø 60 nm. The new vertical structure provides simple fabrication steps and better performance in terms of stability and antenna integration. The THz output power itself can be increased due to high...

A photocathode based on n-doped graphene emitters in series to a GaAs photoswitch was fabricated and used for pulsed field electron emission. The n-doped graphene array emits at low turn-on fields (< 3 V/µm). A fast photomodulation of the emission current with high on/off ratio ~200 was achieved with a semi-insulating (s.i.) GaAs photoswitch in a d...

NEW device concepts and materials for the fabrication of compact THz sources are of particular interest. Compact THz sources involve optical laser mixing, including resonant plasmonic structures at THz and optical frequencies to locally enhance the electromagnetic fields. Of particular interest is the usage here of Graphene, which is optically tran...

Graphene possesses intrinsic plasmons that are tunable and adjustable and the combination of graphene with semiconductors promises a variety of exciting applications. The versatility of graphene means that graphene-based plasmonics may enable the manufacture of novel THz devices. Plasmons are collective density oscillations of an electron cloud and...

Turkish Journal of Physics h t t p : / / j o u r n a l s . t u b i t a k . g o v . t r / p h y s i c s / Abstract: New device concepts and materials for the fabrication of compact high-frequency vacuum sources and micro-nano-integrated X-ray sources are of particular interest for broadband communication, security screening of packages and chemical...

A new type of continuous-wave (CW) terahertz (THz) photomixer was fabricated using a single nanowire (Ø 120 nm) on low-temperature-grown (LTG) GaAs. The small diameter of the nanowire reduces the device capacitance by a factor of more than 10 compared to photomixers with conventional interdigital fingers. Furthermore, the single nanowire can handle...

A simple photocathode based on graphene nanoplatelets glued on semi-insulating (s.i.) GaAs was fabricated and used for field electron emission in a diode configuration. The graphene nanoplatelets act as field emitter array with low turn­ on field. The photomodulation was achieved with a GaAs photoswitch in series to the bottom of the graphene nanop...

A new photomixer and electrode configuration, especially useful in connection with photomixing devices and processes is suggested, which shows much lower capacitance C between the top contact, photoconductive material and bottom contact.

A new type of continuous-wave (CW) terahertz (THz) emitter was fabricated using multilayer graphene (MLG) electrodes on LTG-GaAs photomixer instead of metal electrodes. Unique graphene properties allow high optical power illumination for high photocurrent generation and show the potential for reliable CW THz emission.

A FEBIP-(Focused Electron Beam Induced Processing) - System is used to develop a novel miniaturized tunable, portable THz source for 0.1 to 6 THz. The control voltage with the high frequency is generated using a miniaturized Dynatron oscillator. An oscillator is connected to the anode of the Dynatron triode which modulates the anode voltage due to...

A high-frequency photocathode based on carbon nanotube (CNT) blocks on semiisolating GaAs or low-temperature grown GaAs was fabricated and used for electron emission in a diode configuration. The CNT blocks can achieve high currents and current densities of I=0.5 mA and J=28 mA/cm2 at E=2.1 V/μm, respectively. The photomodulation was achieved with...