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Ultra-broadband THz spectroscopy based on photomixing in air plasma allows to exploit an extended frequency range, up to 20 THz and beyond. In this work, we investigate the potential of this technique for chemical recognition of illicit substances like explosives and compare the experimental spectra with ab-inition DFT simulation results to get deeper insight to the physical nature of the observed...
THz air photonics allow for the generation and detection of single-cycle sub-40 fs THz transients, which we use in a THz time-domain spectrometer to investigate the transmission properties of molecular crystalline materials in the ultrabroadband frequency window from 0.3 THz to more than 40 THz. We compare the obtained results with FTIR measurements to validate the THz-TDS results at large frequencies...
Sources of spectrally broadband and coherent light are necessary for frequency metrology and ultrashort pulse generation. Near-infrared (NIR) wavelengths are practical for such devices because of the emergence of robust and reasonably priced femtosecond lasers operating in this part of spectrum. This further enabled pulse preserving and coherent, so called all-normal dispersion supercontinuum (ANDi...
We generate supercontinuum (817–2250 nm at −30dB) in a dispersion-engineered silicon-rich nitride waveguide by pumping fs pulses with 82 pJ from an erbium-fiber oscillator. Spectral broadening mechanisms include soliton fission and dispersive wave generation.
East China Grid is a branch of the State Grid Corporation of China that operates the largest regional power grid in China which provides electricity to four provinces and Shanghai, about 258 million people. As the national leader in the development of offshore wind farms and nuclear power plants, East China Grid is also the primary receiving end of national ultra-high voltage backbone power grids...
We develop a novel algorithm to implement collision warning to avoid traffic rear-end accidents, in which one vehicle would hit the vehicle running in front. Real-time traffic risk would be computed and the drivers would get informed the warning message. The experiments results show that our algorithm can have effective influence on this problem.
Supercontinuum generation covering an ultra-broad spectrum from 1.5–11.7μm and 1.4–13.3μm is experimentally demonstrated by pumping an 85mm chalcogenide step-index fiber with 100fs pulses at a wavelength of 4.5μm and 6.Зμm, respectively.
In order to further improve the level of intellectualization and informatization for inland river ships, this paper defines the concept of intelligent pre-alarm/alarm system for inland rivers shipping, and puts forward the structure of the system. According to the information provided by ship navigation equipment and shore-based cloud services platform, designs 12 kinds of types, voice service contents...
Self-defocusing soliton compression supported by the cascaded phase-mismatched second-harmonic generation process is numerically demonstrated in unpoled lithium niobate ridge waveguides where nano-joule pulses are operated and quasi-phase-matching is unnecessary. The soliton range is 1100–1800 nm.
An octave-spanning mid-IR supercontinuum is observed experimentally using ultrafast cascaded nonlinearities in an LiInS2 quadratic nonlinear crystal pumped with 70 fs energetic mid-IR pulses and cut for strongly phase-mismatched second-harmonic generation.
A new high-energy pulse compressor uses self-defocusing spectral broadening in anomalously dispersive quadratic nonlinear crystals, followed by positive group-delay-dispersion compensation. Compression to sub-50 fs is possible from Joule-class 1.03 µm femtosecond amplifiers in large-aperture KDP.
Experiments on cascaded quadratic soliton compression in unpoled phase-mismatched lithium niobate waveguides are presented. Pulse self-phasemodulation dominated by an overall self-defocusing nonlinearity is observed, with an variation of pump wavelength and waveguide core width.
Traffic congestion has been a crucial problem nowadays due to the limited traffic resources, which lead to an urgent need for the optimization of current transportation scheduling. In this paper, a real-time traffic-responsive strategy has been proposed, that the timings and periods of traffic signals are optimized adapt to the dynamically changing environment. Simulations also have been conducted...
A popular crystal for ultrafast cascading experiments is beta-barium-borate (β-BaB2O4, BBO). It has a decent quadratic nonlinear coefficient, and because the crystal is anisotropie it can be birefringence phase-matched for type I (oo → e) second-harmonic generation (SHG). For femtosecond experiments BBO is popular because of low dispersion and a high damage threshold. The main attractive property...
The frequency-resolved optical gating (FROG) technique is one of the most popular and robust methods for ultrashort laser pulse characterization [1], which involves an experimental apparatus to create a spectrogram of a target pulse resulting from its convolution with a gate function and a retrieval algorithm.
Generating few-cycle energetic and broadband mid-IR pulses is an urgent current challenge in nonlinear optics. Cascaded second-harmonic generation (SHG) gives access to an ultrafast and octave-spanning self-defocusing nonlinearity: when ΔkL >> 2π the pump experiences a Kerr-like nonlinear index change Δn = ncascI, where ncase ∝ −d2eff/Δk, and deff is the effective quadratic nonlinearity. Due...
Quadratic cascading response is evoked during the ultrafast and phase mismatched (cascading limit) second harmonic generation (SHG) process, which becomes more and more recognized alongside with typical nonlinear phenomena such as nonlinear phase change, pulse intrinsic self-steepening (SS) and material Raman effects. The mean value (local component) of this cascading response has been widely investigated...
3-color coherent anti-Stokes Raman scattering (CARS) can be used to measure the dynamics of vibrationally excited states by controlling the time delay between the broadband and narrowband pulses. It is promising to simultaneously obtain the CARS spectra in time-frequency domains and monitor vibration dephasing times of multiple Raman modes, which is especially favourable in the studies of molecular...
Cascading quadratic nonlinearity [1,2] is well known as an effective nonlinear phase change (n2, casc, Kerr-like) during the ultrafast and phase-mismatched second harmonic generation (SHG) process. The sign and intensity of such an equivalent Kerr nonlinearity (electronic cubic nonlinearity) is closely related to the phase mismatch (Ak) between the fundamental wave (FW) and the second harmonic (SH)...
This paper analyzed the contradictions between requirements for computer software talents in application-oriented undergraduate universities (AOUUs) and current teaching status. We also discussed the necessities of teaching team construction for computer software specialties based on university-enterprise-cooperation (UEC) in AOUUs. We proposed the construction principles and explored the organizational...
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