Proceedings, IEEE Tenth International Conference on Terahertz Electronics
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Self-consistent rate equation modelling of a Terahertz GaAs/AlGaAs quantum-cascade laser
In this work, electron transport in GaAs/AlGaAs quantum cascade lasers operating
at far-infrared wavelengths is calculated self-consistently using an
intersubband scattering model. Subband populations and carrier transition rates
are calculated and all relevant electron-electron and electron-LO phonon
scatterings between the injector/collector and active region levels (13-levels
in total) are incl...
#Equations #Gallium arsenide #Laser modes #Quantum cascade lasers #Particle scattering #Electrons #Phonons #Laser transitions #Temperature distribution #Threshold current
Efficient THz-emitters for low-temperature-grown GaAs photomixers
Different design techniques have been applied to low-temperature grown (LT-)
GaAs photomixers and the respective antennas to increase the efficiency and
output power of these devices. High DC-photocurrents have been achieved with
interdigitated structures and transmission lines have been used to improve
matching between antenna and photomixer. The input impedances of antenna
structures on GaAs sub...
#Gallium arsenide #Impedance #Fingers #Photoconductivity #Substrates #Conductivity #Voltage #Power transmission lines #Biomembranes #Molecular beam epitaxial growth
Far-infrared spectroscopy of hydrogen bonding in nucleobases, nucleosides, and nucleotides
The far-infrared dielectric properties of organic acids and bases in the
condensed phase are dominated by hydrogen bonding between the individual
molecules. We have investigated the dielectric properties of nucleobases,
nucleosides, and nucleotides. We find that at cold temperatures distinct
vibrational modes are present in the frequency range 0.1-4 THz. These modes
originate from ordered hydrogen...
#Spectroscopy #Hydrogen #Bonding #DNA #Electromagnetic wave absorption #Pulse shaping methods #Dielectrics #Temperature distribution #Frequency #Molecular biophysics
Enhancement of THz emission from semiconductor surfaces
We have studied the generation of coherent pulses of terahertz (THz) radiation
from semiconductor surfaces both experimentally and using a Monte-Carlo carrier
dynamics simulation. Collimated THz beams are observed from surface-field THz
emitters and three methods of improving the efficiency of these emitters are
demonstrated: (i) by applying a magnetic field, (ii) by reducing the effective
refract...
#Surface emitting lasers #Semiconductor lasers #Optical pulses #Quantum cascade lasers #Optical pulse generation #Photonic band gap #Charge carrier processes #Gas lasers #Power lasers #Laser excitation
THz 2002. 2002 IEEE Tenth International Conference on Terahertz Electronics Proceedings (Cat. No.02EX621)
- 2002
Presents the front cover of the proceedings record.
An ultra-wide bandwidth photomixer with down conversion at terahertz frequency
We report on the development of an-ultra-broad band photoconductive detector,
based on low-temperature-grown GaAs, vertically-integrated with terahertz spiral
antennas. Velocity overshoot was expected in the photo-response facing the
dramatic decrease in conversion efficiency due to a very short carrier lifetime.
Photomixing experiments with two optical 0.8 /spl mu/m laser beating shows a
3-dB ban...
#Bandwidth #Frequency conversion #Optical pumping #Optical frequency conversion #Photoconductivity #Detectors #Gallium arsenide #Spirals #Charge carrier lifetime #Laser modes
Novel concept for THz-photomixer based on periodically doped heterostructures and quasi ballistic transport
Reports on a new concept for THz photomixers, which are not (as usually)
frequency limited by the carrier lifetime in low-temperature-grown GaAs. The
concept is based on ballistic electron transport in a periodically doped
heterostructure (p-i-n-p-i-n-superlattice) and allows for impedance matching to
the attached antenna.
#Gallium arsenide #Charge carrier processes #Spontaneous emission #Ballistic transport #Frequency #Charge carrier lifetime #Electron mobility #Space charge #Power lasers #Impedance matching
Coherent and incoherent intersubband dynamics
Presents time-resolved measurements of photoinduced intersubband absorption in
an undoped GaAs/AlGaAs coupled quantum well excited by an ultrashort interband
optical pulse. An interband pump pulse injects electrons into the first and
second subband of an undoped asymmetric double quantum well (ADQW) with a level
spacing smaller than the LO phonon energy. The time evolution of the electron
populati...
#Quantum cascade lasers #Optical pulses #Pulse measurements #Probes #Gallium arsenide #Optical pulse generation #Substrates #Zinc compounds #Laser beams #Absorption
What constitutes a useful and meaningful terahertz image?
This contribution attempts to answer the questions of how THz images are best
processed, analyzed, presented, classified and interpreted, especially within a
clinical setting. The solutions to these problems are reviewed within the
context of recent imaging work on tumours and dental tissue, largely conducted
by the Teravision group. It is concluded that compound images, especially those
involving...
#Mie scattering #Rayleigh scattering #Biomedical materials #Particle scattering #Frequency #Water #Biological materials #Filters #Biomedical imaging #Physics
Continuous wave terahertz quantum cascade laser
Reports continuous wave operation of a 4.4 THz unipolar injection quantum
cascade laser grown in the AlGaAs/GaAs materials system by molecular beam
epitaxy. The device operates at 4 K with a threshold current of 160 mA, and an
output power of /spl sim/25 /spl mu/W. In pulsed mode the maximum operating
temperature is 52 K with a threshold current of 108 mA at 4 K.
#Quantum cascade lasers #Temperature #Laser modes #Semiconductor lasers #Solid lasers #Gallium arsenide #Molecular beam epitaxial growth #Threshold current #Frequency #Optical materials