Ultra-short Range Research Articles

Ultra-short wavelength of 1.7 μ m ultrafast Tm-doped fiber laser

Thulium-doped fiber lasers (TDFLs) operating at 1.7 μm have immense potential for multiphoton microscopy and imaging applications. However, further research and development are needed, particularly in the ultra-short wavelength range below 1720 nm. Herein, we demonstrate the mode-locked TDFL at 1.7 μm, utilizing a microfiber InSb saturable absorber. By employing intracavity filters, optimizing the gain fiber length, and incorporating a broadband evanescent field absorber, we achieve high-performance ultra-short wavelength solitons in the TDFL. The solitons exhibit a central wavelength of 1707 nm, a pulse width of 895 fs, a repetition rate of 23.36 MHz, and a single pulse energy of 1.7 nJ. Moreover, our experiments demonstrate the generation of diverse soliton states, including high-order harmonic and bound solitons. We also explore the dynamics of mode-locking through experimental investigations. Our findings establish a solid foundation for the research and control of diverse 1.7 μm mode-locked operation state, advancing the field of ultrafast fiber lasers in this wavelength band.

Effect of Initial Conditions Sampling on Surface Hopping Simulations in the Ultrashort and Picosecond Time Range. Azomethane Photodissociation as a Case Study

We tested the effect of different ways of sampling the initial conditions in surface hopping simulations, with a focus on the initial energy distributions and on the treatment of the zero point energy (ZPE). As a test case, we chose the gas phase photodynamics of azomethane, which features different processes occurring in overlapping time scales: geometry relaxation in the excited state, internal conversion, photoisomerization, and fast and slow dissociation. The simulations, based on a semiempirical method, had a sufficiently long duration (10 ps) to encompass all of the above processes. We tested several variants of methods based on the quantum mechanical (QM) distributions of the nuclear coordinates q and momenta p, which yield, at least on the average over a large sampling set, the correct QM energy, namely the ZPE when starting from the ground vibrational state. We compared the QM samplings with the classical Boltzmann (CB) distribution obtained by a thermostated trajectory, whereby thermal effects are taken into account, but the ZPE is utterly ignored. We found that most QM and CB approaches yield similar results as to short time dynamics and decay lifetimes, whereas the rate of the ground state dissociation reaction CH3NNCH3 → CH3NN + CH3 is sharply affected by the sampling method. With QM samplings a large fraction of trajectories dissociate promply (<1 ps) after decay to the ground state and with rates of the order of 10-1 ps-1 after the first ps. Instead, the CB samplings yield a much smaller fraction of prompt dissociations and much lower rates at long times. We provided evidence that the ZPE "leaks" from high frequency modes to the reactive ones (N-C bond elongations), therefore unphysically increasing the dissociation rates with QM samplings. We show that an effective way to take into account the ZPE and to avoid the "leaking" problem is to add the ZPE to the potential energy surfaces as a function of the most relevant internal coordinates. Then, Boltzmann sampling can be done as usual, so this approach is suitable also for condensed state dynamics. In the tests we present here, the ZPE correction method yields dissociation rates intermediate between QM and uncorrected Boltzmann samplings.

Energy transfer between Si nanocrystals and protoporphyrin molecules as a function of distance, orientation and size.

The interaction between protoporphyrin molecules (donor) and Si nanocrystals (acceptor) up to 2.5nm for varying distances and orientations is studied by DFT, semi-empirical and TDDFT methods. Simulations show an effect on electronic structure, indicative of electron charge transfer in parallel orientation and small distances and nonelectron energy transfer for different orientations and larger distances. An absorption-emission spectral overlap is observed. The calculations of coupling and energy transfer rates show a distance dependence typical of fluorescence resonance energy transfer (FRET) in the long range, while in the short and ultra-short range the distance dependence indicates electron transfer in addition to FRET. The Si NCs with the smallest size yield larger couplings than the larger nanocrystals. The PPIX/Si NC coupling was enhanced by adding a plasmon nanoparticle as a bridge in the donor-acceptor system. Results using Au nanoparticles show increased energy transfer rates up to 104 and lower distance dependence.

Enhanced Probabilistic Route Stability (EPRS) Protocol for Healthcare Applications of WBAN

Wireless Body Area Network (WBAN) is among the most promising technologies for enhancing life quality. WBANs enable constant monitoring of physiological processes by implanting or wearing small, low-power, intelligent sensor nodes in or on the human body. These sensor nodes may be placed either invasively or non-invasively. Patient data must be disseminated reliably and promptly for WBAN’s healthcare apps to function. For this reason, medical teams may use real-time apps for sharing vital information like blood pressure, an ECG, and an EEG. Critical data packets are delay-sensitive and must arrive at sink nodes within the time constraints that satisfy QoS for WBAN. However, networks’ unpredictable and dynamic nature (node mobility, link partitioning) makes reliable data transfer a challenging task. Additionally, postural mobility and ultra-short wireless range cause rapid topology changes, resulting in network partitioning. The network partitioning causes failure of data delivery to the sink or coordinator and causes a delay as well. In the case of normal data, it is not a big issue, but it is not tolerable for emergency data because it may be life-threatening. Consequently, compromising the link reliability and stability results in higher delays, increased packet re-transmissions, and decreased throughput performance. Therefore, we propose an Enhanced Probabilistic Route Stability (EPRS) scheme to address these issues. The proposed EPRS scheme introduces a cost function called Link Assessment Cost (LAC) that makes coherent decisions regarding route reliability in determining whether an active route is a good candidate for routing and satisfying QoS requirements. The LAC is based on two critical factors about link status, i.e., Route Stability Factor (RSF) and Expected Probability of link <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$E(p)$ </tex-math></inline-formula> . Based on these factors, a score is assigned to a link that determines the status (likelihood) of a link, either connected or disconnected. In this way, the multi-facet EPRS selects the most stable and reliable routes despite the disconnection in the networks, thereby improving the route stability and throughput, minimizing the end-to-end delay, route discovery calls, and re-transmissions as depicted by simulation results.

A hybrid relative navigation algorithm for a large–scale free tumbling non–cooperative target

In this paper, the relative navigation problem of a large–scale free tumbling non–cooperative target is investigated. Given that the target cannot be completely captured by navigation sensors in an ultra–short range due to its large size, a hybrid relative navigation algorithm is proposed based on the data fusing principle of monocular cameras and Lidar sensors. First, an algorithm of vision aided point cloud segmentation was developed to improve the data processing efficiency of Lidar. Next, an attitude determination method was proposed for the target via a pure geometrical approach, which is robust to sensor errors. Then, a target geometrical recognition was performed based on a simultaneous localization and mapping (SLAM) approach. Finally, the feasibility and effectiveness of the proposed methods were verified by numerical simulations, indicating that the new relative navigation framework is capable of more accurate attitude tracking of the target with synchronous geometrical recognition than classic attitude tracking methods.

Effect of temporal distance in the ultrashort pulse range on the ablation of polypropylene with single pulses and burst pulses

This research focuses on the ablation process of Polypropylene by femtosecond pulses. Single Pulses and bursts of 2, 3 and 4 pulses have been used to ablate squared cavities with side lengths of 2 mm. The pulse overlap and hatch distance have been adapted to the different pulse emitting modes used in the present study to ensure that the same fluence have reached the cavity in each case. A comprehensive study was performed to assess the effect of the temporal distance between pulses and bursts on the cavity depth and morphology, ablation efficiency and recast layer height.The laser parameters that provide the best results in terms of minimum redeposited material and maximum ablation efficiency have been obtained.

Polarization-based surface enhanced Raman scattering from single colloidal DNA decorated with 3 nm silicon nanoparticles

Surface enhanced Raman scattering (SERS), in which sample molecules are placed in the proximity of conducting nanostructures, subjects the molecules to intense electron oscillation (plasmon) field. The intense field, however, may cause heavy distortion and thermal damage to the molecule as well as non-separable and heavy convolution with the metal electronic structure. We utilized 3-nm red luminescent Si nanoparticles decorating the DNA molecules (drawn electrostatically) to enhance Raman scattering in solution at 532 nm. We demonstrated that the nanoparticles enhance the spectral resolution and intensity of vibrations of DNA by two orders of magnitude and reveal vibrations that are otherwise weak or forbidden. Theoretically, we conducted calculations of Mie scattering and three-dimensional finite-difference time-domain scattering and obtained the wavelength dependence of the near-field distribution from single or dimer Si particles. The simulations show moderate intensity enhancement (25–40-fold) and exciton resonances. Moreover, it shows that the near field is highly confined, extending only to 3–5 Å from the Si particle (atomic scale) compared to several nanometers for metal nanoparticles. The observed SERS-type characteristics are understood in terms of polarization-based light scattering, which is possible by the use of Si of highly reduced size for which the polarizability and exciton processes are strong. However, multilayers contribute to metal SERS, and monolayers/single molecules dominate the Si case. Weaker but highly confined, ultra-short range polarization-based scattering provides an alternative to plasmon and Mie scattering, while providing practical, straightforward interpretation of vibration printing of bio-medical species without compromising the molecular structure.

Properties of Electric Conducting Magnetic Composites in the Ultrashort Range of Radio Waves

A study is made of the radio-shielding and radio-absorbing properties of three-phase ECOM-P/graphite/paraffin composites in the ultrashort range of wavelengths. The effect the concentration of components of the radioabsorbing filler of a composite has on its dielectric permittivity, losses, and electrical conductivity is determined.

Vibrational decoherence induced by ultrafast intramolecular charge separation of an asymmetric bianthryl derivative.

Coherent wavepacket oscillation accompanying the ultrafast photoexcited intramolecular charge separation (CS) of 9,9'-bianthryl (BA) and 10-cyano-9,9'-bianthryl (CBA) in a room temperature ionic liquid, N,N-diethyl-N-methyl-N-(methoxyethyl)ammonium tetrafluoroborate (DemeBF4), was investigated by femtosecond time-resolved transient absorption spectroscopy. The frequency of the coherent oscillation observed for CBA in nonpolar n-hexane solution (Hex) was 377 cm-1, while this oscillation was undetectable in DemeBF4. For BA in DemeBF4, coherent oscillation with a frequency of 394 cm-1 was observed, which is similar to that for CBA in Hex. CS of CBA occurs in the ultrashort time range of ≤100 fs, while that of BA occurs in a few picosecond range [E. Takeuchi et al., J. Phys. Chem. C 120, 14502-14512 (2016)]. Hence, the oscillation of CBA in Hex and that of BA in DemeBF4 are assigned to the molecular vibration in the locally excited state, while this oscillation dephases instantaneously for CBA in DemeBF4 due to the ultrafast CS and no oscillation was generated in the CS state. This result suggests that the CS reaction is not mediated by a specific intramolecular vibration in the CS state but occurs incoherently through higher levels of multiple vibrational modes.

The pulses propagation beyond ultra-short range in the systems of optical communication via higher-order nonlinear Schrödinger equation with derivative non-Kerr nonlinear terms

The higher-order nonlinear Schrodinger equation with derivative non-Kerr nonlinear terms is studied in this work. The pulses propagation beyond ultra-short range in the systems of optical communication is described through this dynamical model. The modified extended direct algebraic technique is utilized for deriving different kinds exact solutions such as bright–dark solitons, kink and anti-kink solitons, solitary waves, periodic solutions and elliptic function solutions of this dynamical model. These achieved exact solutions are more general and are useful to researcher for understanding physical phenomena. The structures of some solutions at suitable values of parameters are presented and helpful for knowing the physical interpretation. Several solutions are novel by comparing these solutions with existing solutions. The power and effectiveness of current can observed form constructed solutions.

The weakly nonlinear wave propagation theory for the Kelvin-Helmholtz instability in magnetohydrodynamics flows

Abstract In this paper, the weakly nonlinear wave propagation theory in the occurrence of magnetic fields in fluids of superposed is studied. The amplitude evolution of governing equations of the amplitude of the progressive waves is reported. The soliton and other kinds solutions of (2+1)-dimensional elliptic nonlinear Schrodinger equation is constructed. We also investigate the properties of envelope of the (2+1)-dimensional wave pocket. The propagation of pulses ahead of ultra-short range in the optical communication systems is illustrated by this dynamical equation. The modified and extended rational expansion method is utilized for obtaining different kinds of wave solutions such as bright-dark solitons, solitons of Kink and anti-Kink, solitary waves, periodic solutions and elliptic function solutions of this equation. These achieved exact solutions are further general and useful to researcher for understanding physical phenomena. Several solutions are novel by comparing these solutions with existing solutions. The power and effectiveness of current can observed form constructed solutions.

Doppler-Resilient 802.11ad-Based Ultrashort Range Automotive Joint Radar-Communications System

We present an ultrashort range IEEE 802.11ad-based automotive joint radar-communications (JRC) framework, wherein we improve the radar's Doppler resilience by incorporating Prouhet-Thue-Morse sequences in the preamble. The proposed processing reveals detailed microfeatures of common automotive objects verified through extended scattering center models of animated pedestrian, bicycle, and car targets. Numerical experiments demonstrate 2.5% reduction in the probability of false alarm at low signal-to-noise-ratios and improvement in the peak-to-sidelobe level dynamic range up to Doppler velocities of $\pm 144$ km/h over conventional 802.11ad JRC.

Integration of the GPR and radio-impedance techniques in studies of the Baikal rift zone

R adio wave propagation techniques have been very rarely applied to investigate tectonic fault zones and geoelectric profiles of the Baikal rift zone. In our study, we used a combination of g round-penetrating radar (GPR) and radio impedance techniques in order to identify and investigate tectonic crustal fault zones in the study area. Using soundings in the super-long, long and ultra short radio wave ranges (from tens of KHz to few GHz ) , we detected the tectonic fault zones in t he seismically active Baikal rift zone , specifically in the Tunk a depression and the areas of South ern Baikal and Kotokel lake s. Faults and fault zones were identified from impedance variations and changes in the geoelectric profiles by analyzing the radio impedance profiles and soundings in the super-long and long radio wave ranges . The georadi o location of fault structures in the ultra-short wave range made it possible to differentiate the patterns of tectonic disturbances up to individual seismic dislocations in sedimentary and crystalline rocks and to determine the kinematics of movements in the fault zone s . The techniques used in this study complement each other and ensure obtaining adequate quantitative descri ptions of the study object s . By i ntegrati ng various techniques of radio wave diagnostics , it is possible to obtain more detailed information on the structure s of the tectonic fault zones . The results obtained in this study and the radio impedance and GPR sounding and profiling techniques developed to investigate a heterogeneous underlying medium can be used in seismological and geological engineering surveys of the eastern and northern regions of Russia.

Molecular lattice clock with long vibrational coherence

Atomic lattice clocks have spurred numerous ideas for tests of fundamental physics, detection of general relativistic effects, and studies of interacting many-body systems. On the other hand, molecular structure and dynamics offer rich energy scales that are at the heart of new protocols in precision measurement and quantum information science. Here we demonstrate a fundamentally distinct type of lattice clock that is based on vibrations in diatomic molecules, and present coherent Rabi oscillations between weakly and deeply bound molecules that persist for 10's of milliseconds. This control is made possible by a state-insensitive magic lattice trap that weakly couples to molecular vibronic resonances and enhances the coherence time between molecules and light by several orders of magnitude. The achieved quality factor $Q=8\times10^{11}$ results from 30-Hz narrow resonances for a 25-THz clock transition in Sr$_2$. Our technique of extended coherent manipulation is applicable to long-term storage of quantum information in qubits based on ultracold polar molecules, while the vibrational clock enables precise probes of interatomic forces, tests of Newtonian gravitation at ultrashort range, and model-independent searches for electron-to-proton mass ratio variations.

Novel solitons and elliptic function solutions of (1 + 1)-dimensional higher order nonlinear Schrödinger equation with derivative non-Kerr nonlinear terms and its applications

The propagations are generally described through nonlinear Schrödinger equation (NLSE) in the optical solitons. In the NLSEs, the higher order NLSE with derivative non-Kerr nonlinear terms is a model that depicts propagation of pulses beyond ultra-short range in optical communication system. Several novel exact solutions of different kinds such as solitons, solitary waves and Jacobi elliptic function solutions are achieved via using modified extended mapping technique. Different kinds of exact results have prestigious exertions in engineering and physics. Structures of solitons different kinds are shown graphically by giving suitable values to parameters. The physical interpretations of solutions can be understand through structures. Several exact solutions and computing work confirm the supremacy and usefulness of the current technique.

Study of soliton solutions of higher-order nonlinear Schrödinger dynamical model with derivative non-Kerr nonlinear terms and modulation instability analysis

Abstract In this work, soliton solutions of higher order non-linear Schrodinger equation (NLSE) with derivative non-Kerr non-linear terms are constructed by employing two analytical techniques, namely, exp ( - Φ ( ζ ) ) -expansion and improved simple equation methods. This dynamical model plays a key role in engineering and physics, and it can be equation of pulses promulgation behind ultra-short range in the system of optical communication. The constructed soliton solution helps researchers for understanding the physical phenomenon of this equation. The standard linear stability analysis is utilized and the stability of model is investigated which substantiate that all results are stable and exact. Graphically, the movements of some solutions are depicted at appropriate values of parameters. The achieved results shows simplicity, reliability and power of the current schemes.

Solitons and other solutions for higher-order NLS equation and quantum ZK equation using the extended simplest equation method

In this article, we apply the extended simplest equation method for constructing the solitons and other solutions of two nonlinear partial differential equations (PDEs), namely the higher-order nonlinear Schrödinger (NLS) equation with derivative non-Kerr nonlinear terms and the nonlinear quantum Zakharov–Kuznetsov (QZK) equation which play an important role in mathematical physics. The first equation describes pulse of the propagation beyond ultrashort range in optical communication systems, while the second equation arises in quantum magneto plasma. Comparison of our new results in this article with the well-known results is given.

The $$\left( \frac{\boldsymbol{G}^{\prime }}{\boldsymbol{G}},\frac{\boldsymbol{1}}{\boldsymbol{G}}\right)$$ G ′ G , 1 G -expansion method and its applications for constructing many new exact solutions of the higher-order nonlinear Schrödinger equation and the quantum Zakharov–Kuznetsov equation

In this article, we apply the two variable $$\left( \frac{G^{\prime }}{G}, \frac{1}{G}\right)$$ -expansion method with the aid of symbolic computation to construct many new exact solutions for two higher-order nonlinear partial differential equatuions (PDEs) namely, the higher-order nonlinear Schro dinger (NLS) equation with derivative non-kerr nonlinear terms describing pulse of the propagation beyond ultrashort range in optical communication systems and the higher-order nonlinear quantum Zakharov–Kuznetsov (QZK) equation which arises in quantum magneto plasma . Also, based on Lienard equation, we find many other diffrent new soliton solutions of the above NLS equation. Soliton solutions, periodic solutions, rational functions solutions and Jacobi elliptic functions solutions are obtained. Comparing our new solutions obtained in this article with the well-known solutions are given.

Many new exact solutions to the higher-order nonlinear Schrödinger equation with derivative non-Kerr nonlinear terms using three different techniques

Many new types of Jacobi elliptic function solutions, solitons and other solutions to the higher-order nonlinear Schrödinger equation with derivative non-Kerr nonlinear terms have been found using three mathematical techniques, namely, the special kind of (G′/G)-expansion method, the ϕ6-model expansion method and the new mapping method. This equation could be a model equation of pulse propagation beyond ultrashort range in optical communication systems. This model is photonic crystal fiber (PCF). Comparing our new results with the well-known results are given. Also, we compare the results yielding from the three methods with each other.

Self-similar localized pulses for the nonlinear Schrödinger equation with distributed cubic-quintic nonlinearity

We obtain the exact analytical self-similar bright-, dark-, and kink-solitary-wave solutions of the nonlinear Schr\odinger equation with localized inhomogeneous cubic-quintic nonlinearity by employing a similarity transformation. This equation could be a model equation of stable pulse propagation beyond ultrashort range in optical fiber communication systems in inhomogeneous media. We have investigated that the self-similar bright- and dark-solitary-wave solitons show interesting compression and amplification features that can be controlled by suitably changing the phase modulation parameter and consequently varying the nonlinear parameter. We unearth a surprising connection between optical self-similar localized waves in graded-index inhomogeneous media and solitons in homogeneous media with the same type of cubic-quintic nonlinearity. Finally, the stability of the solutions is discussed numerically under finite initial perturbations.