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A family of aperiodic Mo/Be multilayer mirrors was designed for maximum uniform reflectivity in the ranges 111 – 138, 111 – 150, 111 – 200 and 111 – 222 Å at normal radiation incidence. The simulations took into account the existence of Mo-on-Be and Be-on-Mo transition layers. It was shown that the reflectivity may be as high as 10% in an octave wavelength range of 111 – 222 Å. We demonstrate the operation of an imaging transmission-grating spectrograph with a broadband Mo/Be multilayer mirror with a uniform reflectivity in the wavelength range 111 – 138 Å synthesised at the Institute for the Physics of Microstructures, RAS. The spectrograph was used to record the line spectra of multiply charged fluorine and magnesium ions from a laser-produced plasma. The role of the grating support structure in the formation of spectral source images is discussed. The spatial resolution of 50 μm is demonstrated.

Vibration vehicle models provide a great opportunity to integrate vehicle-based vibrations into a mechanical engineering vibrations course. This paper documents and discusses an approach to a multiple-degree-of-freedom (MDOF) in regards to pitch and bounce of the vehicle body with dampening and stiffness observed. The approach utilizes hand calculations, OCTAVE, and ANSYS to solve speed-bump induced vibration and to calculate vibrations modes. The problem involves a bicycle-model approach to a vehicle’s response when subject to a speed bump, or a sudden impulse load upon the forward-face of the model. These responses are captured and analyzed on pitch and bounce of the model at the center-of-gravity and the front/rear sides of the model. Graphical models capture responses of the loading conditions and the modal equations of the model providing a method of studying and understanding vibrational responses under provided stiffness. Using ANSYS as an approach of the model to capture damping response, further graphical models can be captured and used to describe motions of the vehicle model’s center-of-gravity, frontward and rearward wheel assembly, and the pitch (rotation) of the center-of-gravity to the introduced responses. A successful study with analysis of each graphical element and further dissemination of the results is concluded.

We present the temporal characterization of infrared pulses with spectra extending from 0.55 to 2.5 μm by using the frequency resolved optical switching (FROSt) technique. The pulses are obtained by broadening femtosecond pulses at 1.75 μm central wavelength in a two-stage hollow core fiber setup. This work demonstrates the capability of the FROSt technique to temporally characterize pulses with ultra-broadband spectra. Being free of phase-matching constraints, it enables the characterization of pulses with very low energy at the limit of the detection threshold and with arbitrary long pulse duration. This strength of the FROSt technique is illustrated by the characterization of supercontinua pulses whose spectra span over two octaves and with only 150 nJ energy that is spread temporally over almost 40 ps. The FROSt capabilities provide a versatile tool for the characterization of sub-cycle pulses and to study nonlinear processes such as supercontinuum generation.

We have developed a broadband and high-precision terahertz (THz) frequency counter based on a semiconductor-superlattice harmonic mixer (SLHM). Comparison of two THz frequencies determined using two independent counters and direct measurement of frequency-stabilized THz-quantum cascade lasers by a single counter showed a measurement uncertainty of less than 1 × 10−16 over a four-octave range from 120 GHz to 2.8 THz. Further extension of this measurable range was indicated by the research regarding the higher-harmonics generation of a local oscillator for the SLHM. This compact and easy-to-handle THz counter operating at room temperature is available for high-resolution spectroscopy of ultracold molecules proposed for detecting temporal changes in physics constants as well as many THz applications requiring a wide measurement range without a bulky cryogenic apparatus.

We phase locked an octave-spanning optical frequency comb based on a laser-diode-pumped Kerr-lens mode-locked Yb:KYW laser to a reference laser. We controlled the cavity length of the mode-locked laser to phase lock the mode frequency of the comb to the reference laser. This was conducted using a fast piezoelectric-actuated mirror on a lead-filled mount, which was aimed at damping the mechanical resonances. We achieved a servo bandwidth of 200 kHz, a residual phase noise of 0.47 rad, and a power concentration to a carrier of 91%. To extend the locking duration of the carrier-envelope offset frequency, we compensated its slow drift using the position of the Yb:KYW crystal while the pump-laser power was controlled to achieve its phase locking. We continuously maintained the full phase locking of the comb for 3 h until the reference lasers were out of lock.

This paper presents the experimental work on a new tube-shape electromagnetic vibration energy harvester to obtain its optimum peak-to-peak voltage output based on different stroke length, number of coil turns and optimum frequency. The harvester is fabricated using Acrylonitrile Butadiene Styrene (ABS) material. It consists of housings with three different stroke lengths, top and bottom covers, Neodymium Iron Boron (NdFeB) magnets, spring and copper coil. The tested stroke lengths are 40 mm, 45 mm and 50 mm while the number of coil turns are 10, 20 and 30. A standard energy harvesting circuit which consists of full-wave bridge rectifier and a capacitor is designed and fabricated to conduct this experiment. The importance of this circuit is to convert alternating current (AC) to direct current (DC) as well as to enable harvesting and storing processes of electrical energy. The harvester is tested on external vertical vibrations generated by shaker with frequency ranged from 5 Hz to 50 Hz with interval of 5 Hz. The raw voltage readings have been extracted from Oscilloscope and are analysed using Microsoft Excel and Octave software. From the results obtained, the optimum peak-to-peak voltage harvested is 39.41 mV at resonant frequency of 5 Hz by 50 mm stroke length and 30 coil turns device. The higher the stroke length and number of coil turns, the higher the peak-to-peak voltage can be harvested.

The paper presents the analysis results of medium heavy vehicle traffic measurements which were used to simulate the noise measurands. The Cnossos-EU model were used for this purpose. The medium heavy vehicle traffic volume and velocity were recorded by permanent automatic sound and traffic monitoring station. The noise was calculated in octave bands according to the Cnossos-EU model. The results were described using parameters such as the median, average peak level – C90, average background noise level – C10, percentiles C25 and C75. Analyzes carried out for the tested section of the road showed that the traffic of medium heavy vehicles is one of the main source of road noise. It has been shown that maximum values of the equivalent sound level occur for the frequency of f0 = 1 kHz. The positional measures of traffic noise were proposed for data scattering. The dispersion of noise and type A uncertainty of the results were evaluated. It was found that in most cases, the distribution of the tested variable was not normal. It was notice a lack of symmetry between the time distribution of traffic flow of vehicles entering and leaving the city.

We formulate an approach to the development of stigmatic high-resolution spectral instruments for the soft X-ray range (λ ≤ 300 A), which is based on the combined operation of normalincidence multilayer mirrors (including broadband aperiodic ones) and grazing-incidence reflection gratings with nonequidistant grooves (so-called VLS gratings). A concave multilayer mirror serves to produce a slightly astigmatic image of the radiation source (for instance, an entrance slit), and the diffraction grating produces a set of its dispersed stigmatic spectral images. The width of the operating spectral region is determined by the aperiodic structure of the multilayer mirror and may range up to an octave in wavelength.

We present a source of brilliant mid-infrared radiation, seamlessly covering the wavelength range between 1.33 and 18 μm (7500–555 cm−1) with three channels, employing broadband nonlinear conversion processes driven by the output of a thulium-fiber laser system. The high-average-power femtosecond frontend delivers a 50 MHz train of 250 fs pulses spectrally centered at 1.96 μm. The three parallel channels employ soliton self-compression in a fused-silica fiber, supercontinuum generation in a ZBLAN fiber, and difference-frequency generation in GaSe driven by soliton self-compressed pulses. The total output enables spectral coverage from 1.33 to 2.4 μm, from 2.4 to 5.2 μm, and from 5.2 to 18 μm with 4.5 W, 0.22 W and 0.5 W, respectively. This spatially coherent source with a footprint of less than 4 m2 exceeds the brilliance of 3rd-generation synchrotrons by more than three orders of magnitude over 90% of the bandwidth.

We demonstrate a high-power, octave-spanning, Kerr-lens mode-locked Ti:sapphire laser using double-chirped mirrors to precisely compensate for intracavity dispersion. The ultra-broadband spectrum spans from 550 nm to 1100 nm and the few-cycle pulse is as short as 6.6 fs with an average power up to 880 mW corresponding to the peak power of 1.6 MW. This is, to the best of our knowledge, the highest average output power directly achieved from an octave-spanning Ti:sapphire laser oscillator at the repetition rate of 80 MHz. In addition, the third-order harmonically mode-locked phenomenon was observed in our experiments.

This study was proposed to get the solution of the Schrodinger equation with cotangent hyperbolic potential in the presence of minimal length by using the hypergeometric method. By getting the numerical results with the help of Octave software, we can analyze nonrelativistic energy. The visualization of wave function was obtained using Matlab software. The result is defined as the larger of minimal length, the width of potential V1, and the angular momentum was included, the energy is increasing as well. The larger of the width of potential V0 affected the decrease of energy in this system.

We present the analysis and design of a multi-octave broadband microwave absorber with simultaneous high optical transparency. Assisted by the semi-analytical method, the proposed metamaterial absorber, composed of transparent dielectric substrates and patterned indium–tin–oxide, can achieve an excellent electromagnetic wave absorption in a wide frequency band from 6.21 GHz to 19.31 GHz within a total thickness of only about 0.075λ. The experiment results are in agreement with full-wave simulations, demonstrating high-efficient and broadband absorption in a wide angular range from 0° to 45° for all polarizations. In addition, by substituting the middle layers with flexible dielectric layer, we successfully design a flexible metamaterial absorber for conformal applications. The performance of conformal absorber is also verified by simulation and experiment, both of which validate an excellent backward scattering suppression for cylinder object with wavelength-comparable radius. With advantages of excellent absorption, polarization-insensitivity, thin-thickness and especially high transmittance and flexibility, the proposed absorber may have potential uses in many real-world applications.

We synthesized Cr3+, Cr4+-codoped Mg2SiO4 phosphors and studied their optical properties for application as a novel wideband near-infrared (NIR) light-source. The phosphors have an ultra-wideband NIR luminescence spectrum of 650–1400 nm. The origin should be the transition of Cr3+ and the transition of Cr4+. The luminescence spectrum spans over one octave range and covers the "optical window in biological tissues". We successfully achieved an ultra-wideband luminescence of 650–1400 nm with a maximum output power of 367.5 μW by combining a blue LED with Cr3+ and Cr4+-codoped Mg2SiO4 phosphors in a single package.

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In order to determine the radiated sound power of an underwater source below the Schroeder cut-off frequency in a non-anechoic tank, a low-frequency extension measuring technique is proposed. This technique is based on a unique relationship between the transmission characteristics of the enclosed field and those of the free field, which can be obtained as a correction term based on previous measurements of a known simple source. The radiated sound power of an unknown underwater source in the free field can thereby be obtained accurately from measurements in a non-anechoic tank. To verify the validity of the proposed technique, a mathematical model of the enclosed field is established using normal-mode theory, and the relationship between the transmission characteristics of the enclosed and free fields is obtained. The radiated sound power of an underwater transducer source is tested in a glass tank using the proposed low-frequency extension measuring technique. Compared with the free field, the radiated sound power level of the narrowband spectrum deviation is found to be less than 3 dB, and the 1/3 octave spectrum deviation is found to be less than 1 dB. The proposed testing technique can be used not only to extend the low-frequency applications of non-anechoic tanks, but also for measurement of radiated sound power from complicated sources in non-anechoic tanks.

Carrier-envelope phases (CEPs) from a kHz repetition rate, non-CEP stabilized laser system are measured and tagged with two different methods: an f–2f interferometer and a stereo-above-threshold-ionization carrier-envelope-phase-meter. Both methods utilize the octave spanning spectrum generated in the hollow-core fiber (HCF) that broadens the laser spectrum to produce few-cycle pulses. Phases from both methods are carefully synchronized and compared on a single shot level. The results show that the CEPs measured by both methods are in good agreement and demonstrate that a HCF based f–2f interferometer is well suited for CEP tagged experiments.

The particle-in-the-box, with or without an additional potential, is proposed as an excellent laboratory to teach and explore the details of the linear variational method using a non-orthogonal basis. The xn(a − x)n and xn(a/2 − x)(a − x)n polynomials are shown to form a complete basis for the even and odd states, respectively, of the particle confined to the x [0, a] interval. A short and simple Octave code is presented as the natural extension to the hand calculations when the basis set grows in size.

Melilite-type Ba2MgGe2O7 was found to be an attractive, simultaneously χ(2)- and χ(3)-active nonlinear optical crystal. Under one-micron picosecond pumping we observed several manifestations of nonlinear interactions, namely almost sesqui-octave Stokes and anti-Stokes lasing combs, collinear and ``Cherenkov''-type SHG, THG, SFG, and cascaded self-conversion χ(3) ↔ χ(2) generation in the visible and UV range. All recorded lasing components were identified and attributed to a single SRS-promoting vibration mode ωSRS = 771.5 cm-1. A short review of melilite-type compounds is given.

We report the experimental investigation of nonlinear cascaded lasing χ(3) ↔ χ(2) effects in UV and visible ranges and high-order Stokes and anti-Stokes generation covering spectral space of about 18000 cm-1 by stimulated Raman scattering and multi-wave mixing processes under one-micron picosecond pumping in the paraelectric state of NH4H2PO4 and ND4D2PO4 single crystals. All recorded Raman induced laser wavelengths are identified and attributed to their SRS-promoting vibration modes. Brief review of nonlinear-laser processes in non-centrosymmetric phosphates of KH2PO4-family and some physical properties of NH4H2PO4 and ND4D2PO4 are given as well.

Using numerical simulations, a wideband (>1.5 octave) vane loaded helix traveling-wave tube (TWT) was studied, the output section of which is provided with a `positively' phase velocity tapered helix portion, in which the helix pitch is made to linearly increase with distance towards the output end for reasonably high efficiency values. As compared to a device with a conventional 'negatively' phase velocity tapered helix portion, which gives an efficiency hike only in a narrow band of frequency, the positively tapered device provided a wideband efficiency improvement. Also, over the band, it provided a higher efficiency and a lower second harmonic content than a device with a nontapered portion. Factors such as the beginning position of the taper from the input and the amount of taper were considered in the optimum design for improving efficiency and reducing the second harmonic content of the device.

Aiming at the problem that it is difficult to extract the feature information from the space bearing vibration signal because of different noise, for example the running trend information, high-frequency noise and especially the existence of lot of power line interference (50Hz) and its octave ingredients of the running space simulated equipment in the ground. This article proposed a combination method to eliminate them. Firstly, the EMD is used to remove the running trend item information of the signal, the running trend that affect the signal processing accuracy is eliminated. Then the morphological filter is used to eliminate high-frequency noise. Finally, the components and characteristics of the power line interference are researched, based on the characteristics of the interference, the revised blind source separation model is used to remove the power line interferences. Through analysis of simulation and practical application, results suggest that the proposed method can effectively eliminate those noise.

We demonstrate a system based on telecom components for the generation of a coherent octave-spanning supercontinuum from a continuous-wave laser. The system utilizes direct multiplication of a 10 GHz signal derived from a commercial synthesizer to carve pulses from the laser, which are then iteratively chirped and compressed in two stages. After reducing the repetition rate of the resulting pulse train to 2.5 GHz using selective transmission through an electro-optic gate, propagation through highly-nonlinear fiber generates an octave-spanning supercontinuum spectrum. We discuss the impact of the noise of the modulation frequency on the coherence of the supercontinuum and discuss its mitigation. Close agreement between experiment and theory is shown throughout, and we use our ability to precisely model the experiment to propose an extension of the system to 20 GHz repetition rate.

We report the recent results on development of a CEP-stable 1 kHz repetition rate TW-class OPCPA system driven by femtosecond Yb:KGW and picosecond Nd:YAG pump sources. Seed pulses with spectra spanning over an octave are produced in a continuum generator pumped by CEP-stable pulses from a difference frequency generator operated at 1.3–1.6 μm. After amplification in NOPA, pulses with energy up to 70 μJ and spectra supporting durations of 5 fs are obtained. Sub-70 mrad CEP jitter at the output of system frontend is demonstrated.

Infrared pulses with large spectral width extending from 1.2 to 3.4 μ m are generated in the organic crystal DAST (4-N, N-dimethylamino-4′-N′-methylstilbazolium tosylate). The input pulse has a central wavelength of 1.5 μ m and 65 fs duration. With 2.8 mJ input energy we obtained up to 700 μ J in the broadened spectrum. The output can be easily scaled up in energy by increasing the crystal size together with the energy and the beam size of the pump. The ultra-broad spectrum is ascribed to cascaded second order processes mediated by the exceptionally large effective χ 2 nonlinearity of DAST, but the shape of the spectrum indicates that a delayed χ 3 process may also be involved. Numerical simulations reproduce the experimental results qualitatively and provide an insight in the mechanisms underlying the asymmetric spectral broadening.

The quantum correlation of octave-spanning time–energy entangled bi-photons can be as short as a single optical cycle. Many experiments designed to explore and exploit this correlation require a uniform spectral phase (transform-limited) with very low loss. So far, transform-limited single-cycle bi-photons have not been demonstrated, primarily due to the lack of precise, broadband control of their spectral phase. Here, we demonstrate the correction of the spectral-phase of near-octave spanning bi-photons to over an octave in frequency –2600 nm). Using a prism-pair with an effectively negative separation for shaping the bi-photons' spectral phase, we obtain a tuned, very low-loss compensation of both the second and fourth dispersion orders. An essential requisite for precise tuning over such a broad bandwidth is a measure of the spectral phase that provides feedback for the tuning even when the overall dispersion is far from compensated. This is achieved by a non-classical bi-photon interference, which enables direct verification of the corrected bi-photon spectral phase.

We demonstrate third-harmonic generation (THG) with a tunable spectral range of more than 500 nm in a step-index tellurite fiber. Third-harmonic (TH) signals with a peak wavelength from 524 to 1043 nm are obtained in a 3 cm-long fiber when the fundamental wavelength shifts from 1560 to 3100 nm. To our knowledge, the tunable spectral range covering almost one octave is the widest tunable range of THG in fibers so far. The far-field patterns of the TH signals by 1560 nm to 2100 nm pumping are recorded by a charge coupled device camera, which are close to the fundamental mode profile. The THG in such a wide tunable range is attributable to the high nonlinearity of the tellurite fiber and the high pump peak power of the pump pulse.

A 51 fs, 4.4 nJ, almost-pedestal-free, high-power ultrashort pulse was generated using an Er-doped similariton amplifier. Using the generated ultrashort pulse, high-power, octave-spanning coherent supercontinua broadened from 1.05 to 2.15 and 0.95 to 2.3 µm were generated in highly nonlinear fibers. The characteristics of the similariton amplifier were investigated experimentally.

This paper introduces a novel SRS-active crystal, hexagonal CaS2O6 4H2O, which was found to be an attractive Raman gain material and a suitable subject for the study of numerous nonlinear lasing effects. Under picosecond laser pumping in the UV, visible and near-IR spectral region we observed various manifestations of Raman induced nonlinear interactions. All registered Stokes and anti-Stokes components are identified and attributed to the participating .3/ -promoting phonon modes. In the appendix, we present new data on the SRS properties of another dithionate, Na2S2O6 2H2O. (Some figures may appear in colour only in the online journal)

The supercontinuum (SC) generation in all-normal dispersion (ANDi) photonic-crystal fiber (PCF) pumped by high power picosecond pulses are investigated in this paper. Our results show that an octave SC may be achieved by pumping the ANDi PCF with picosecond pump pulses. However, the PCF length required may have to be lengthened to several tens of centimeters, which is much longer than that with femtosecond pump pulses. The relatively long PCF gives rise to much higher Raman gain and stronger Raman frequency shift compared to those with femtosecond pump pulses, which in turn not only cause a distorted temporal waveform and an un-flattened spectrum, but also severely degrade the coherence of the generated SC.

Natural crystals of topaz, Al2(F1−x(OH)x)2SiO4 were found to be an attractive Raman gain material and a subject for the investigation of different χ(3)-nonlinear optical effects. We present several manifestations of photon–phonon interactions related to SRS and RFWM processes initiated by picosecond excitations at room and cryogenic (≈9 K) temperature. Among them are octave-spanning Stokes and anti-Stokes generation in the visible and near-IR spectral range, combined SRS-active phonon modes, cross-cascaded up-conversion, χ(3)↔χ(3) lasing, as well as THG via self-sum frequency parametric generation. All recorded Raman-induced lasing lines are identified and attributed to the promoting χ(3)-vibration transitions. Based on the experimental data, theoretical simulations employing Fourier analysis are performed to demonstrate the potential of wide SRS frequency combs in terms of ultra-short pulse generation.

We demonstrate an octave-spanning Kerr-lens mode-locked Ti:sapphire laser with double-chirped mirrors (DCMs), BaF2 wedges and plate, which generates laser pulses in the spectrum range from 600 nm to 1200 nm at −45 dB below the maximum and the duration of 8.5 fs at the repetition rate of 80 MHz. The average output power is 100 mW under 5 W pump power. By carefully adjusting the insertion of BaF2 wedges and the optimization position of Ti:sapphire crystal in the cavity, we can obtain the smooth swings in the interferometric autocorrelation trace due to good third-order dispersion compensation.

Thermoacoustic carbon nanotube (CNT) speakers were fabricated using CNT webs spun from a multiwalled carbon nanotube (MWNT) array of 0.8–1.6 mm height. The generated sound pressure level (SPL) showed a linear relationship with frequency over a wide range from 10 Hz to 40 kHz with a slope of 6 dB/octave. In addition to this, significantly broad and flat SPLs were obtained in the ultrasonic region, ranging from 40 to 100 kHz. The distance from the speaker to the microphone was 0.5 m. The high SPL is due to the good heat radiation property of the MWNT web. Herein, we showed an acoustical property for the MWNT web thermoacoustic speaker from the viewpoint of the structural web morphology. The role of heat radiation behavior and the effects of the length of individual MWNTs are discussed.

A design is given for a low-noise limited oscillator whose inherent sensitivity is then sacrificed for the practical convenience of having remotely controlled varicap diode tuning and small diameter probes. A series of seven probes, each tunable over more than an octave, covers 1.36 to 60 MHz in overlapping ranges.

An argon-filled thyratron is used to generate a continuous noise spectrum for audio-frequency testing. Large unwanted ultrasonic components are removed from the output by a 20 kc/s low-pass filter, leaving a noise spectrum having constant power per cycle/second band-width over the audio-frequency range. Where required, a noise having constant power per octave bnad-width is produced by adding a weighting network. The output into 600 ohms is -20 db with reference to 1 mW. The generator is mains operated.