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Filling the terahertz gap
Towards a new generation of sources, detectors and sensors
in the “no man’s land” between photonics and electronics
Gaetano Scamarcio1,2, Miriam Serena Vitiello3,4, Vincenzo Spagnolo1,2
1
Dipartimento Interateneo di Fisica, Università degli Studi di Bari “Aldo Moro” e Politecnico di Bari, Bari, Italy
Consiglio Nazionale delle Ricerche, Istituto di Fotonica e Nanotecnologie, UOS Bari, Italy
3
Consiglio Nazionale delle Ricerche, Istituto di Nanoscienze and Laboratorio NEST, Pisa, Italy
4
Scuola Normale Superiore, Pisa, Italy
2
Recent breakthroughs in nanotechnologies are pushing up the efficiency of compact semiconductor laser sources
and detectors of radiation in the terahertz (THz) range of the electromagnetic spectrum. At these frequencies, many
molecules have their spectroscopic fingerprints due to rotational and vibrational transitions. Hence, long-dreamed
killer applications of THz photonics such as sensing, imaging, diagnostics, coherent spectroscopy in strategic fields
like medicine, microelectronics, petrochemical industry, forensic science, cultural heritage are coming true.
1 Introduction
The terahertz region of the
electromagnetic spectrum
conventionally identifies radiation with
frequencies in the range 100 GHz–
10 THz, or equivalently, wavelengths in
the range 3 mm–30 µm, energies in the
range 0.4–40 meV. From a fundamental
point of view, both generation
and detection of THz radiation in
semiconductor heterostructures rely
on the interaction with either bound or
free electrons, in the realms of optics or
electronics, respectively. The efficiencies
of electronic devices based on the
interaction with free electrons depends
on the strength of oscillatory currents
excited by the electric field of the
optical waves, and dramatically drops
beyond the microwaves region due
to saturation of the electron velocity.
In addition, the strength of photon
absorption or emission associated
with transitions between subbands
created by quantum confinements in
quantum well structures is governed
by the strength of polarization currents,
which drops with decreasing frequency
in the infrared. Hence, due to inherent
technical difficulties related with the
lack of practical and efficient sources
and detectors the THz electromagnetic
range is still underdeveloped, a fact
usually referred to as the existence of a
so-called “THz gap”. On the other hand,
while microwave technologies encroach
the lower-frequency side, optical
technologies have made tremendous
advances in the last decade in the
higher-frequency side.
In this article, we will review recent
milestones to fill the THz gap. We
will present the state-of-the-art of
quantum cascade lasers (QCLs), which
are considered the most promising
compact sources of THz wave [1]. The
discovery that high-mobility graphene
or low-dimensional semiconductor
channels in field effect transistors
(FETs) can act as plasma waves cavities
to detect THz radiation [2] marks an
outstanding progress in the field
of long-wavelength photonics. The
quest for smaller, faster and sensitive
optoelectronics devices is a strong
driving force behind developments
in nanoscale science and technology.
Remarkable progress has been recently
achieved with the development of onedimensional [3] and two-dimensional
[4] FETs in which high-mobility
semiconductors can act as cavities for
plasma waves to detect THz radiation
via nonlinear rectification of the ac
current induced by the oscillating
radiation field.
The recent innovation in the
performance of photonic sources
and detectors is now enabling
THz technologies to be employed
in an increasingly wide variety of
applications, such as information
and communications technologies,
medical and biological sciences, global
environmental monitoring, homeland
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security, industrial quality and process controls. Most of the
above applications exploits the THz spectroscopic features
of materials. In fact, explosives, narcotics, and toxic gases
have distinct spectral “fingerprints” and strong absorption
bands associated with rotational and vibrational transitions
across the THz range. Also, THz radiation is weakly absorbed
by non-metallic and non-polarizing materials (e.g. textiles,
paper, ceramics, plastics, undoped semiconductors), which
makes these materials transparent while they are opaque at
visible frequencies. Being non-ionizing, THz beams are safe
for biological and medical imaging applications, unlike X-rays.
All these properties makes THz technologies ideal for imaging
and sensing applications. Among sensing techniques, quartz
enhanced photoacoustic spectroscopy (QEPAS) based
on QCLs has demonstrated its competitive advantages
with respect to other spectroscopies [5]. Its recent first
demonstration in the THz range will be reviewed [6].
2 Quantum cascade lasers
It is commonly accepted that the quantum cascade laser
([1] and refs. therein) is the most striking demonstration
of bandgap engineering. In fact, in these devices all
relevant physical parameters can be controlled by spatial
confinement in semiconductor heterostructures thanks
to the extreme precision achievable in the design via the
quantum engineering of electronic wave functions on a
nanometer scale and the state-of-the-art epitaxial material
growth. QCLs are unipolar device that exploits inter-subband
transitions between quantum confined electronic states
of the conduction band. While the idea of using intersubband transitions for electromagnetic amplification was
theoretically proposed long before their realization, it was
the development of molecular beam epitaxy (MBE) or
metalorganic vapor phase epitaxy (MOCVD) that provide
unprecedented control of layer thickness down to a single
atomic monolayer, necessary to put in practice the QCL
concept. Indeed, a key feature of QCLs is the ability to create
sharp discontinuities in the conduction band edges, thereby
controlling the size quantization effects on charge carriers at
nanometer scale, the related tuning of the electronic energy,
the electron localization, the transport as well as the optical
transition processes.
The main feature of the QCL is the possibility to tune
its emission frequency over a wide range by tailoring
the thickness of quantum wells and barriers, while
keeping the same semiconductor material system. This is
markedly different with respect to conventional interband
semiconductor lasers, in which the emission wavelength
depends on the material bandgap and the gain is strongly
temperature-dependent. Remarkably, the cascaded structure
makes possible that each electron injected above threshold
may generate a number of photons larger than one and even
equal to the number of active region stages.
For subband separations larger than longitudinal optical
(LO) phonon energy ELO (32–36 meV in III-V semiconductors),
Fig. 1 Best reported performance of quantum cascade lasers. Plot of the maximum
reported operating temperatures as a function of the emission wavelength (or frequency,
top axis). Reproduced with permission from ref [1], ©2015, OSA.
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g. scamarcio et al.: Filling the terahertz gap
energy relaxation processes in QCLs are controlled by
emission of LO phonons. The LO-mediated scattering is
the dominant inter-subband scattering mechanism, with
scattering times approximately 1 ps or less. For intersubband transitions in which the separation is less than
ELO , emission of LO-phonons is energetically forbidden at
low temperatures. Non-radiative relaxation is therefore
dominated by the combination of electron-electron (e-e)
scattering, electron-impurity scattering, and LO-phonon
scattering of the high-energy tail of the subband electron
distribution. However, even when devices are operated at
low temperature, a non-equilibrium electron distribution
may exist [7–11]. Intrasubband LO-phonon scattering is an
important process in cooling the subband electron gas while
the effect of intrasubband e-e scattering is to thermalize the
electron distribution inside a particular subband.
Although QCLs may be realized using almost any
semiconductor material system, the best performance has
been obtained by using either GaInAs/AlInAs grown on InP
substrates in the mid-IR, or GaAs/AlGaAs grown on GaAs
substrates in the THz. After two decades from their invention,
QCLs operating in the mid-IR have reached impressive
performance levels. Spectral coverage has been achieved at
wavelengths in the range 3 μm–25 μm with the potential for
large tunability [12]. In 2002, operation range of QCLs was
extended to the THz region [13], although still at cryogenic
temperatures. Figure 1 schematically shows the present state
of available frequencies as a function of the temperature
performances of QCLs. Room temperature, CW operation of
mid-IR QCLs was achieved more than 10 years ago and the
last decade has witnessed a dramatic improvement that has
made it possible to reach emitted powers on the order of
several watts. The wall-plug efficiency, i.e. the ratio between
injected and emitted power, has reached values as high as
27% in pulsed mode and 21% in CW mode [14] with more
than 5 W of CW output power at room temperature.
These impressive performances are due to a combination
of refined quantum engineering of the laser active region,
together with a refined material growth, advanced processing
solutions like buried heterostructures and epi-down
mounting providing efficient management of dissipated heat.
3 Terahertz quantum cascade lasers
Quantum cascade lasers offer a very promising route to
cover the upper frequency range of the THz gap. At present,
THz QCLs have been demonstrated to work in the frequency
range 1.2–4.9 THz. Power levels of a few milliwatts are typical,
and large area devices have recently demonstrated even
watt-level output powers [15]. However, in spite of a decade
of effort, THz QCLs are still limited to cryogenic operation. The
highest reported temperatures in pulsed mode operations
is 200 K [16], while in continuous-wave operation the upper
bound is 129 K [17]. These performances have been achieved
using the so-called resonant-phonon active region design,
([18] and refs. therein) schematically shown in fig. 2.
Fig. 2 Terahertz quantum cascade laser. Scheme of the so-called resonant-phonon active region showing two modules of the calculated
conduction band diagram (black line) obtained by the alternate growth of GaAs quantum wells and AlGaAs quantum barriers by molecular beam
epitaxy. The colored lines show the square moduli of the wave functions obtained solving the Schrödinger equation in the envelope function
approximation. The applied electric field correspond to the band alignment for lasing. Electrons are injected by tunneling into level 2. Laser action
(wavy arrow) occurs between levels 2 and 1. Efficient depletion of level 1 is obtained by designing the energy difference between level 1 and the
injector states (inj) equal to an LO-phonon energy (~ 36 meV). Reproduced with permission from ref. [18], ©2007, Nature Publishing group.
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Looking for an explanation and possibly finding a correction
for the poorer thermal performance of THz QCLs with respect
to mid-IR ones, has been the subject of extensive investigation.
On one side, THz QCLs are qualitatively different from the
mid-IR ones for two reasons: the photon energy is smaller than
the LO-phonon one; losses by free carrier scattering cannot
be neglected, since they scale as λ2 and even lightly doped
semiconductor layers can contribute significantly. This poses
important constraints on the laser design. The calculations of
active regions have to include the injection and depopulation
of carriers with high precision into the closely spaced energy
levels. In addition, the laser waveguides must be designed to
minimize the overlap with doped regions.
There is a general consensus on the major impediment
to room temperature operation of THz QCLs. It is ascribed
to the reduction of the optical gain at higher temperatures
due to thermally activated energy relaxation paths allowing
transitions between the upper and lower radiative states
via optical-phonon emission [18, 19]. At low electronic
temperatures this scattering path is suppressed, since
ℏωTHz < ELO , (ELO = 36 meV in GaAs). However, at high
temperatures electrons in the upper radiative subband gain
sufficient in-plane kinetic energy to emit an LO-phonon and
relax to the lower subband. This process, sketched in fig. 3,
causes the upper-state lifetime to decrease exponentially with
increasing electronic temperature. This in turn reduces the
gain and eventually leads to laser shutoff.
The most straightforward approach to improve the
operating temperature is to explore novel active region
designs within the GaAs/AlGaAs material system. Several
designs have been demonstrated using an “indirect injection”
scheme, where electrons are injected into the upper radiative
state not by resonant tunneling, but by LO-phonon scattering
from a higher-energy state [20]. This scheme, similar to the
one successfully demonstrated also for mid-IR QCLs, [8, 21]
adds flexibility to design and can in principle help to suppress
sub-threshold parasitic leakage currents which plague THz
QCLs. Good results have been obtained with this approach
at lower frequencies and it seems likely that this scheme will
be most useful for lasers emitting < 2.5 THz where parasitic
currents are the most problematic.
The lack of success in reaching room temperature
operation using GaAs/AlGaAs-based QCLs is motivating
the exploration of other III-V material systems. So far, none
of these materials has matched the performance of GaAs/
AlGaAs designs. In principle, the use of III-nitride quantum
wells is promising since GaN has an LO-phonon energy of
92 meV and hence thermally activated LO-phonon scattering
should be dramatically suppressed at room temperature. Still,
nitride quantum wells have proven to be very challenging to
grow for vertical transport applications.
Other more radical approaches are also actively explored.
For example, implementing a cascade laser in quantum
dots instead of quantum wells would allow to suppress
non-radiative scattering by exploiting the so-called “phononbottleneck” mechanism to eliminate electronic states at the
LO-phonon resonance energy, thereby suppressing both
relaxation and dephasing scattering. So far, efforts to use selfassembled quantum dots embedded in quantum wells have
not been successful at demonstrating lasing but has led to
renewed interest in the “top-down” etching of semiconductor
nanowires.
Fig. 3 Scheme of the main process responsible for thermal quenching of lasing
in THz QCLs. Calculated dispersion of the upper (2) and lower (1) laser subands.
At high temperature, electrons in the subband 2 may acquire enough energy
to scatter to subband 1 by non-radiative LO-phonon emission.
2
1
hot electron
E
ELO
k
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g. scamarcio et al.: Filling the terahertz gap
Because of these difficulties in achieving room temperature
operation, there has been considerable effort to leverage
the advances in high-power two-color mid-IR QC-lasers
for intracavity THz difference frequency generation (DFG)
at room-temperature. Indeed, the remarkable power
performance of mid-IR QCLs has already allowed the
development of room temperature, mid-IR–based THz
sources relying on intra-cavity DFG [22, 23]. The highest
reported output powers to date are 1.4 mW in pulsed mode
and 3 μW in CW mode [23]. The challenges reside primarily in
the conversion and overall wall-plug efficiency, which is ~10–5
or less, and the efficient extraction of the THz radiation, since
free-carrier losses make the mid-IR laser cavity quite lossy for
THz.
Optical frequency combs [24] have revolutionized the fields
of high-precision spectroscopy and metrology as certified
by the attribution of the 2005 Nobel prize in physics to Ted
Hänsch and John Hall. The extension of the comb concept
to all the electromagnetic spectrum is currently involving a
number of technologies, including QCLs. Mid-IR frequency
combs have been already realized starting from pulsed
sources by means of non-linear optics and frequency downconversion. In the last three years, a number of milestones
have been achieved, starting with the first demonstration of
comb operation of a broadband mid-IR QCL [25]. QCL comb
operation has been recently extended also to the THz range,
where the role of dispersion is much stronger than in mid-IR:
the careful compensation of this effect has led to QCL combs
at 3.5 THz [26], thereby opening the way to a very promising
field of applications of high-resolution THz spectroscopy.
4 Terahertz detectors
Conventional detectors of THz radiation are based on
thermal sensing elements, that are typically very slow, e.g.,
Golay cells or pyroelectric elements that can be modulated
up to 10–400 Hz. In addition, to keep low values of noise
equivalent power they need deep cryogenic cooling at
liquid He temperatures. Even those exploiting fast non-linear
electronics (e.g., Schottky diodes) show a dramatic drop of
their performance at frequencies larger than 1 THz.
Recently, by exploiting the gate-modulation of the
conductance channel induced by the incoming radiation, the
possibility of using high-electron-mobility transistors, field
effect transistor (FETs) and metal-oxide-semiconductor FETs
as THz detectors has been demonstrated. Either single-pixel
or even multi-pixel focal-plane array configurations have
been realized in different material systems including Si, GaAs/
AlGaAs, InGaP/InGaAs/GaAs, and GaN/AlGaN.
The recent progress in atomic-to-nanometer scale control
of materials morphology, size, and composition allowed the
fabrication of 2D-FETs based on graphene or 1D-FET based
on semiconductor nanowires (NW), which are ideal building
block for implementing detectors that could be well operated
into the THz range also thanks to their typically ultra-small
capacitance of the order of attofarad.
A very promising scheme is based on the possibility to
engineer the channel of a FET as a resonator for plasma
waves, whose frequency can be properly tailored across
the THz. In this way, gated regions hundreds-nm wide can
support the propagation of collective density oscillations
(plasma waves) at THz frequencies. Under these conditions,
an ac-modulated THz wave funneled into the channel of a
FET can give rise to a rectification effect and be detected
as continuous (dc) source-drain voltage, which can be
maximized by varying the gate bias VG . Rectification is due to
the nonlinear response of the electron gas in the FET channel
and is unrelated to extrinsic rectification mechanisms due
to Schottky barriers at contacts or other circuital elements
that respond in a non-ohmic manner. The induced plasma
oscillations can propagate in the channel or be damped. In
the first case, a strong resonant photo-response is achieved
and channel materials having plasma damping rates lower
than both the frequency of the incoming radiation and the
inverse of the wave transit time in the channel are usually
needed. This condition requires channel material mobility (μ)
of at least several thousand cm2/Vs at frequencies > 1 THz.
In the case of over-damping, the decay occurs on a distance
shorter than the channel length. Eventually, a broadband
THz detection is expected. In any case, in order to induce
a non-zero drain-source voltage it is mandatory to have
some asymmetry between source and drain. This is usually
obtained using an asymmetric THz feeding configuration,
which can be achieved either by using a special antenna
or by an asymmetric design of S and D contacts or even
engineering an anti-symmetric channel, as schematically
shown in fig. 4.
Using semiconductor NWs is a viable approach to develop
THz plasma-wave detectors [27, 28]. This technology
promises a rapid impact on spectroscopy and imaging
applications. The versatility offered by the growth
procedure and the possibility to lithographically “design”
the required asymmetry, mandatory for the rectification
of plasma waves in the transistor channel, make these
devices highly appealing for the development of a compact
multi-pixel detection system. As per the S-D asymmetry, it
can be obtained by modifying the material morphology,
composition, and doping or by properly shaping lowimpedance antennas. The latter system promises to show,
even in a simple two-terminal configuration, high quantum
efficiencies across the THz range. Furthermore, the inherent
attofarad order capacitance of a NW and the related 10 THz
cutoff frequency is ideal to push the devices at very high
speeds (up to nanosecond scales).
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5 Terahertz optoacoustic trace gas sensors
Recent breakthroughs in THz photonics and
nanotechnology are enabling THz frequency research to
be applied in a widespread range of sensing applications.
Optical techniques are competitive with respect to
conventional analytical ones and the THz region offers
additional advantages in terms of selectivity, because gas
molecules have clear absorption spectral “fingerprints”,
arising from rotational quantum transitions. These spectra
allow unambiguous, more efficient and accurate detection
compared to the characteristic vibrational complex
structures in the mid-IR. Consequently, the inherent high gas
specificity together with the short response times (typically
< 1 s) make THz optical sensors suitable for real-time in situ
measurements. A number of THz optical systems based on
quantum cascade lasers (QCLs) have been recently proposed
for gas sensing or spectroscopy. In particular, for highresolution gas spectroscopy, they fully exploit the availability
of distributed feedback or comb-assisted QCLs.
Among trace-gas optical detection techniques, quartzenhanced photoacoustic spectroscopy (QEPAS) is very
attractive since it is capable of record sensitivities using a
compact and relatively low-cost acoustic detection module.
Figure 5 schematically shows the principle of operation. In
the photoacoustic effect, the absorption of light by molecules
produces localized heating and increase of the gas pressure.
Modulating the incident light intensity creates a pressure
wave (sound) at the same frequency of the modulation. The
resulting photoacoustic signal can be amplified by tuning
the modulation frequency to one of the acoustic resonances
of the system [29]. The key advantage of this technique
is that no optical detector is required. In addition, QEPAS
exploits the enhancement of acoustic signal by a sharply
resonant high-quality factor quartz tuning fork (QTF) acting
as piezoelectric acoustic transducer [5].
Efficient QEPAS sensors have been demonstrated for
trace gas detection of several chemical species with a
detection limit of a few parts per trillion in volume [30, 31].
The performance of different types of QEPAS sensors can
be conveniently compared in terms of the normalized
noise equivalent absorption (NNEA), taking into account
the available optical laser power, the selected absorption
line strength and the integration time. Significantly, the
smallest NNEA values are expected in the THz region. In fact,
THz absorption is dominated by rotational levels and their
relaxation rates are up to three orders of magnitude faster
than vibrational ones in the mid-IR. QEPAS signal strongly
depends on the energy relaxation rates of the absorption
gas species and the possibility to work with fast relaxing
transition levels allows operating at low pressure, so taking
advantage of the typically very high QTF Q-factors and
enhancing the selectivity of the QEPAS sensor systems.
In summary, QEPAS in the THz range promises unambiguous,
more efficient and accurate detection compared to the
mid-IR.
Since the sensitivity of QEPAS technique is ultimately
Fig. 4 (a) Image of InAs nanowires taken by a scanning electron microscope. The wire height is typically 1–2 µm;
reproduced with permission from ref. [27], ©2012, ACS. (b) Schematics of a set-up to detect THz radiation emitted
by a quantum cascade laser by a nanowire terahertz detector coupled with a patterned bow-tie antenna.
(c) Antenna-coupled terahertz detector consisting in a log-periodic circular-toothed antenna patterned between
the source and gate of a FET transistor. The drain is a metal line running to the bonding pad; reproduced with
permission from ref. [3], ©2012, AIP Publishing LLC.
48 < il nuovo saggiatore
g. scamarcio et al.: Filling the terahertz gap
limited by the available optical power, QCLs represent the
most promising THz light sources for QEPAS applications.
Recently, by exploiting suitably designed custom QTFs and
THz QCLs, we have reported the first demonstration of QEPAS
sensor operating in the THz range [5, 32] using methanol
as gas target and obtained a record NNEA levels as low as
2×10–10 cm–1 W/Hz1/2. In a subsequent report [33], we have
clearly demonstrated the advantage of THz spectroscopy.
We have selected hydrogen sulfide (H2S) which is a toxic gas
present in oil, natural gas, volcanoes, hot springs, well water
and food. H2S is also a threat to human health and exposure
to high concentration levels will cause unconsciousness and
even death. One of the most important potential applications
of THz QEPAS sensors is H2S detection in natural gas. These
types of measurements cannot be performed using near or
mid-IR optical sensors, due to the ambiguity related to the
dense absorption spectra of the buffer natural gas mixture
(ethane, methane, propane and other hydrocarbons). The
THz range offers a spectral region of simplified absorption
features and hence leads to a potential solution for sensitive
H2S detection in natural gas.
The realized H2S THz QEPAS sensor has shown a value of
the NNEA several times lower than the best result obtained
for H2S in the mid and near-IR [33, 34]. The sensor minimum
detection limit can be further improved by employing QCLs
with higher emission power and with emission frequencies
in resonance with stronger H2S absorption lines, potentially
achieving a detectivity of a few tens of parts per billion.
6 Conclusion
The terahertz range of the electromagnetic spectrum,
where light-matter interaction phenomena based on charge
transport and optical transitions merge, is offering exciting
opportunities to explore a variety of physical effects as well
as countless applications. The roadmap for the development
of THz technologies include, among the others, applications
in the fields of outdoor and indoor communications, security,
drug detection, biometrics, food quality control, agriculture,
medicine, semiconductors, air pollution. The realization of such
applications demands high-power compact THz sources, more
sensitive detectors, and more functional integrated THz systems.
Recent breakthroughs in the fields of quantum cascade lasers,
innovative nanowire-based FET detectors and optoacoustic
spectroscopic systems are significantly contributing in filling the
“THz gap” and bringing this so far underdeveloped region to a
bright future of real life applications.
Acknowledgments
The described researches have been partially supported by
the Italian Ministry for University and Research through the
Italian national Projects Nos. PON02_00675, PON02_00576,
PON 03 “SISTEMA”, and by the European Union through the
MPNS COST Action “MP1204 TERA-MIR Radiation: Materials,
Generation, Detection and Applications”. MSV acknowledges
the program FIRB - Futuro in Ricerca 2010 RBFR10LULP
“Fundamental research on Terahertz photonic devices”.
Fig. 5 Pictorial view of terahertz quartz-enhanced photoacoustic sensor. The gas target absorption of the
modulated terahertz beam emitted by a quantum cascade laser generates pressure waves, which in turn
induces periodic deformations in the quartz tuning fork. Owing to the piezoelectric nature of quartz, the
tuning fork behaves as a transducer and generates a current proportional to the concentration of molecules.
Reproduced with permission from ref. [6], ©2013, AIP Publishing LLC.
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Gaetano Scamarcio
Gaetano Scamarcio received his PhD in physics
from the University of Bari in 1989. Since 2002,
he is full professor of experimental physics at
the University of Bari. He published over 220
research articles on high-impact international
journals and 7 patents. His research interests
include the development and applications
of mid-infrared and terahertz quantum
cascade lasers the study of optical, vibrational
and transport properties of semiconductor
structures at the nanoscale, the development
of spectroscopic techniques for real-time
monitoring of optoelectronic devices. He has
been the recipient of an Award of the Italian
Physical Society in 1989.
50 < il nuovo saggiatore
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Miriam Serena Vitiello
Miriam Serena Vitiello received her PhD in
physics from the University of Bari in 2006. Since
2010 she is a staff research scientist at the
Nanoscience Institute of the National Research
Council and Scuola Normale Superiore in Pisa.
She published over 150 articles on high-impact
international journals. Her research interest
includes the development of THz QCLs, highfrequency nano-detectors, graphene and
2D materials photonics and optoelectronics,
semiconductor nanowire quantum devices,
THz optical waveguides, THz metrology and
high-resolution spectroscopy. She has been
the recipient of the Panizza Award of the Italian
Physical Society in 2012.
Vincenzo Spagnolo
Vincenzo Spagnolo obtained his PhD in physics
from the University of Bari in 1994. From 1997
to 1999, he worked as researcher of the National
Institute of the Physics of Matter (INFM). Since
2004, he is assistant Professor of Physics at
the Politecnico di Bari. His research activity is
documented by more than 130 publications
and 2 patents and include the following
topics: quantum cascade lasers, spectroscopic
techniques for real-time device monitoring,
optoacoustic gas sensors.