scholarly journals Population difference gratings created on vibrational transitions by nonoverlapping subcycle THz pulses

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Rostislav Arkhipov ◽  
Anton Pakhomov ◽  
Mikhail Arkhipov ◽  
Ihar Babushkin ◽  
Ayhan Demircan ◽  
...  
Keyword(s):  
Strong Field ◽  
Modulation Depth ◽  
Resonant Medium ◽  
Thz Spectroscopy ◽  
Thz Radiation ◽  
Population Difference ◽  
Frequency Multiplication ◽  
Perturbative Regime ◽  
Multi Level ◽  
Thz Range

AbstractWe study theoretically a possibility of creation and ultrafast control (erasing, spatial frequency multiplication) of population density gratings in a multi-level resonant medium having a resonance transition frequency in the THz range. These gratings are produced by subcycle THz pulses coherently interacting with a nonlinear medium, without any need for pulses to overlap, thereby utilizing an indirect pulse interaction via an induced coherent polarization grating. High values of dipole moments of the transitions in the THz range facilitate low field strength of the needed THz excitation. Our results clearly show this possibility in multi-level resonant media. Our theoretical approach is based on an approximate analytical solution of time-dependent Schrödinger equation (TDSE) using perturbation theory. Remarkably, as we show here, quasi-unipolar subcycle pulses allow more efficient excitation of higher quantum levels, leading to gratings with a stronger modulation depth. Numerical simulations, performed for THz resonances of the $$H_20$$ H 2 0 molecule using Bloch equations for density matrix elements, are in agreement with analytical results in the perturbative regime. In the strong-field non-perturbative regime, the spatial shape of the gratings becomes non-harmonic. A possibility of THz radiation control using such gratings is discussed. The predicted phenomena open novel avenues in THz spectroscopy of molecules with unipolar and quasi-unipolar THz light bursts and allow for better control of ultra-short THz pulses.

scholarly journals Broadband spectroscopy of astrophysical ice analogues

2019 ◽  
Vol 629 ◽  
pp. A112 ◽  
Author(s):  
B. M. Giuliano ◽  
A. A. Gavdush ◽  
B. Müller ◽  
K. I. Zaytsev ◽  
T. Grassi ◽  
...  
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Time Domain ◽  
Complex Refractive Index ◽  
Far Infrared ◽  
Infrared Region ◽  
Thz Radiation ◽  
The Real ◽  
Thz Range ◽  
The Time Domain

Context. Reliable, directly measured optical properties of astrophysical ice analogues in the infrared and terahertz (THz) range are missing from the literature. These parameters are of great importance to model the dust continuum radiative transfer in dense and cold regions, where thick ice mantles are present, and are necessary for the interpretation of future observations planned in the far-infrared region. Aims. Coherent THz radiation allows for direct measurement of the complex dielectric function (refractive index) of astrophysically relevant ice species in the THz range. Methods. We recorded the time-domain waveforms and the frequency-domain spectra of reference samples of CO ice, deposited at a temperature of 28.5 K and annealed to 33 K at different thicknesses. We developed a new algorithm to reconstruct the real and imaginary parts of the refractive index from the time-domain THz data. Results. The complex refractive index in the wavelength range 1 mm–150 μm (0.3–2.0 THz) was determined for the studied ice samples, and this index was compared with available data found in the literature. Conclusions. The developed algorithm of reconstructing the real and imaginary parts of the refractive index from the time-domain THz data enables us, for the first time, to determine the optical properties of astrophysical ice analogues without using the Kramers–Kronig relations. The obtained data provide a benchmark to interpret the observational data from current ground-based facilities as well as future space telescope missions, and we used these data to estimate the opacities of the dust grains in presence of CO ice mantles.

scholarly journals Observation and quantification of the quantum dynamics of a strong-field excited multi-level system

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Zuoye Liu ◽  
Quanjun Wang ◽  
Jingjie Ding ◽  
Stefano M. Cavaletto ◽  
Thomas Pfeifer ◽  
...  
Keyword(s):  
Quantum Dynamics ◽  
Strong Field ◽  
Level System ◽  
Multi Level

scholarly journals Highly efficient generation of strong-field 0.1-THz radiation

2016 ◽  
Author(s):  
Xiaojun Wu ◽  
Anne-Laure Calendron ◽  
Koustuban Ravi ◽  
Chun Zhou ◽  
Michael Hemmer ◽  
...  
Keyword(s):  
Strong Field ◽  
Thz Radiation ◽  
Highly Efficient ◽  
Efficient Generation

scholarly journals Choice of Polymer Matrix for a Fast Switchable III-V Nanowire Terahertz Modulator

MRS Advances ◽  
2017 ◽  
Vol 2 (28) ◽  
pp. 1475-1480 ◽  
Author(s):  
Sarwat A. Baig ◽  
Jessica L. Boland ◽  
Djamshid A. Damry ◽  
Hoe H Tan ◽  
Chennupati Jagadish ◽  
...  
Keyword(s):  
Polymer Matrix ◽  
Modulation Depth ◽  
Areal Density ◽  
Thz Radiation ◽  
Switching Speed ◽  
Parylene C ◽  
Optical Pump ◽  
High Modulation ◽  
Thz Modulator ◽  
Probe Spectroscopy

ABSTRACTProgress in ultrafast terahertz (THz) communications has been limited due to the lack of picosecond switchable modulators with sufficient modulation depth. Gallium arsenide nanowires are ideal candidates for THz modulators as they absorb THz radiation, only when photoexcited – giving the potential for picosecend speed switching and high modulation depth. By embedding the nanowires in a polymer matrix and laminating together several nanowire–polymer films, we increase the areal density of nanowires, resulting in greater modulation of THz radiation. In this paper, we compare PDMS and Parylene C polymers for nanowire encapsulation and show that a high modulation depth is possible using Parylene C due to its thinness and its ability to be laminated. We characterize the modulator behavior and switching speed using optical pump–THz probe spectroscopy, and demonstrate a parylene–nanowire THz modulator with 13.5% modulation depth and 1ps switching speed.

scholarly journals Organic crystal-based THz source for complex refractive index measurements of window materials using single-shot THz spectroscopy

2021 ◽  
Vol 127 (11) ◽  
Author(s):  
Lufan Du ◽  
Franz Roeder ◽  
Yun Li ◽  
Mostafa Shalaby ◽  
Burgard Beleites ◽  
...  
Keyword(s):  
Refractive Index ◽  
Complex Refractive Index ◽  
Accurate Determination ◽  
Laser Pulses ◽  
Thz Spectroscopy ◽  
Thz Radiation ◽  
Single Shot ◽  
Detection Scheme ◽  
Electro Optic

AbstractWe employed N-benzyl-2-methyl-4-nitroaniline (BNA) crystals bonded on substrates of different thermal conductivity to generate THz radiation by pumping with 800 nm laser pulses. Crystals bonded on sapphire substrate provided four times more THz yield than glass substrate. A pyrodetector and a single-shot electro-optic (EO) diagnostic were employed for measuring the energy and temporal characterisation of the THz pulse. Systematic studies were carried out for the selection of a suitable EO crystal, which allowed accurate determination of the emitted THz spectrum from both substrates. Subsequently, the THz source and single-shot electro-optic detection scheme were employed to measure the complex refractive index of window materials in the THz range.

scholarly journals Extreme nonlinear strong-field photoemission from carbon nanotubes

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Chi Li ◽  
Ke Chen ◽  
Mengxue Guan ◽  
Xiaowei Wang ◽  
Xu Zhou ◽  
...  
Keyword(s):  
Nonlinear Dynamics ◽  
Carbon Nanotubes ◽  
Power Law ◽  
Strong Field ◽  
Modulation Depth ◽  
Incident Light ◽  
Optical Field ◽  
Charge Interaction ◽  
Phase Sensitive ◽  
Electron Pulses

Abstract Strong-field photoemission produces attosecond (10−18 s) electron pulses that are synchronized to the waveform of the incident light. This nonlinear photoemission lies at the heart of current attosecond technologies. Here we report a new nonlinear photoemission behaviour—the nonlinearity in strong-field regime sharply increases (approaching 40th power-law scaling), making use of sub-nanometric carbon nanotubes and 800 nm pulses. As a result, the carrier-envelope phase sensitive photoemission current shows a greatly improved modulation depth of up to 100% (with a total modulation current up to 2 nA). The calculations reveal that the behaviour is an interplay of valence band optical-field emission with charge interaction, and the nonlinear dynamics can be tunable by changing the bandgap of carbon nanotubes. The extreme nonlinear photoemission offers a new means of producing extreme temporal-spatial resolved electron pulses, and provides a new design philosophy for attosecond electronics and photonics.

Population Difference Gratings Induced in a Resonant Medium by a Pair of Short Terahertz Nonoverlapping Pulses

2018 ◽  
Vol 125 (4) ◽  
pp. 586-589 ◽  
Author(s):  
R. M. Arkhipov ◽  
A. V. Pakhomov ◽  
M. V. Arkhipov ◽  
I. Babushkin ◽  
N. N. Rosanov
Keyword(s):  
Resonant Medium ◽  
Population Difference

scholarly journals Terahertz real-time imaging uncooled array based on antenna- and cavity-coupled bolometers

2014 ◽  
Vol 372 (2012) ◽  
pp. 20130111 ◽  
Author(s):  
François Simoens ◽  
Jérôme Meilhan
Keyword(s):  
Real Time ◽  
Direct Detection ◽  
Detection Threshold ◽  
Complementary Metal Oxide Semiconductor ◽  
Industrial Applications ◽  
Oxide Semiconductor ◽  
Thz Radiation ◽  
Quarter Wavelength ◽  
Highly Sensitive ◽  
Thz Range

The development of terahertz (THz) applications is slowed down by the availability of affordable, easy-to-use and highly sensitive detectors. CEA-Leti took up this challenge by tailoring the mature infrared (IR) bolometer technology for optimized THz sensing. The key feature of these detectors relies on the separation between electromagnetic absorption and the thermometer. For each pixel, specific structures of antennas and a resonant quarter-wavelength cavity couple efficiently the THz radiation on a broadband range, while a central silicon microbridge bolometer resistance is read out by a complementary metal oxide semiconductor circuit. 320×240 pixel arrays have been designed and manufactured: a better than 30 pW power direct detection threshold per pixel has been demonstrated in the 2–4 THz range. Such performance is expected on the whole THz range by proper tailoring of the antennas while keeping the technological stack largely unchanged. This paper gives an overview of the developed bolometer-based technology. First, it describes the technology and reports the latest performance characterizations. Then imaging demonstrations are presented, such as real-time reflectance imaging of a large surface of hidden objects and THz time-domain spectroscopy beam two-dimensional profiling. Finally, perspectives of camera integration for scientific and industrial applications are discussed.

scholarly journals Diffraction-limited ultrabroadband terahertz spectroscopy

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
M. Baillergeau ◽  
K. Maussang ◽  
T. Nirrengarten ◽  
J. Palomo ◽  
L. H. Li ◽  
...  
Keyword(s):  
Electric Fields ◽  
Dynamic Range ◽  
Terahertz Spectroscopy ◽  
Thz Spectroscopy ◽  
Thz Radiation ◽  
Large Area ◽  
Broadband Radiation ◽  
Strong Focusing ◽  
Spectroscopy System ◽  
Photoconductive Emitter

Abstract Diffraction is the ultimate limit at which details of objects can be resolved in conventional optical spectroscopy and imaging systems. In the THz spectral range, spectroscopy systems increasingly rely on ultra-broadband radiation (extending over more 5 octaves) making a great challenge to reach resolution limited by diffraction. Here, we propose an original easy-to-implement wavefront manipulation concept to achieve ultrabroadband THz spectroscopy system with diffraction-limited resolution. Applying this concept to a large-area photoconductive emitter, we demonstrate diffraction-limited ultra-broadband spectroscopy system up to 14.5 THz with a dynamic range of 103. The strong focusing of ultrabroadband THz radiation provided by our approach is essential for investigating single micrometer-scale objects such as graphene flakes or living cells and besides for achieving intense ultra-broadband THz electric fields.

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