Values Of Pulse Energy Research Articles

Indium selenide for mode-locked pulse generation in a Mid-infrared Er:ZBLAN fiber laser

Two-dimensional materials are increasingly recognized for their distinctive nonlinear optical properties. Indium selenide (InSe), a notable optoelectronic material, demonstrates unique advantages in terms of nonlinear absorption behavior, making it a promising candidate in mid-infrared mode-locked lasers. By preparing a InSe saturable absorber (SA) and applying it in a Er: ZBLAN fiber laser, we demonstrate a stable mode-locked mid-infrared fiber laser at 2.8 μm. The obtained mode-locked pulses have a repetition frequency and pulse duration of 29.875 MHz and 13.6 ps, respectively. The obtained maximum value of pulse energy is 4.3 nJ. The signal-to-noise ratio (SNR) is 55 dB, indicating the high stability of the laser system. Our experimental results validate that InSe is a promising SA in the near 3 μm band. This work paves the way for further investigations and applications of InSe-based devices in nonlinear optics and mode-locked laser systems.

High data rate and energy efficient configurable IR-UWB transmitter with an integrated balun

This paper presents a novel, digitally configurable, switching oscillator-based impulse radio ultra-wideband (IR-UWB) transmitter that is robust to process variations. The pulse width and pulse position properties of the output waveform are configurable to ensure operation for the desired bandwidth and output pulse energy values. The architecture is based on a cross-coupled LC voltage-controlled oscillator (LC VCO) implemented with a custom-designed on-chip balun at a center frequency of 2.4 GHz. With the usage of this on-chip balun, the need for an extra buffer stage is eliminated, and the highest possible efficiency is achieved with the proper turns ratio selected. The generated digital control pulse signals are also used to ensure fast start-up and UWB operation while maintaining low power consumption with an implemented on/off tail switching scheme. The presented IR-UWB transmitter that occupies a total area of 0.35 mm2 is fabricated in the United Microelectronics Corporation (UMC) 180-nm mixed-mode/radio frequency (RF) CMOS process. The measured output voltage swing of the fabricated transmitter is 0.812 V on a 50-Ω load for the 200 Mb/s data rate, and the bandwidth is measured as 902 MHz. The achieved frequency tuning range is 1 GHz and the fabricated transmitter can drive 50 Ω, 75 Ω and 100 Ω loads with measured efficiency values 4.16%, 5.76%, and 4.05%, respectively. Compared to other works in the literature, this design achieves a higher output pulse energy at a higher data rate while maintaining low power consumption and, thus, high efficiency.

Detection sensitivity of fluorescence lifetime imaging ophthalmoscopy for laser-induced selective damage of retinal pigment epithelium

PurposeTo investigate the sensitivity of fluorescence lifetime imaging ophthalmoscopy (FLIO) to detect retinal laser spots by comparative analysis with other imaging modalities.MethodsA diode laser with a wavelength of 514 nm was applied with pulse durations of 5.2, 12, 20, and 50 µs. The laser pulse energy was increased so that the visibility of the laser spot by slit-lamp fundus examination (SL) under the irradiator’s observation covers from the subvisible to visible range immediately after irradiation. The irradiated areas were then examined by fundus color photography (FC), optical coherence tomography (OCT), fundus autofluorescence (AF), FLIO, and fluorescein angiography (FA). The visibility of a total of over 2200 laser spots was evaluated by two independent researchers, and effective dose (ED) 50 laser pulse energy values were calculated for each imaging modality and compared.ResultsAmong examined modalities, FA showed the lowest mean of ED50 energy value and SL the highest, that is, they had the highest and lowest sensitivity to detect retinal pigment epithalium (RPE)-selective laser spots, respectively. FLIO also detected spots significantly more sensitively than SL at most laser pulse durations and was not significantly inferior to FA. AF was also often more sensitive than SL, but the difference was slightly less significant than FLIO.ConclusionConsidering its high sensitivity in detecting laser spots and previously reported potential of indicating local wound healing and metabolic changes around laser spots, FLIO may be useful as a non-invasive monitoring tool during and after minimally invasive retinal laser treatment.

Minimizing surface roughness and back wall dross for fiber laser micro-cutting on AISI 316 L tubes using response surface methodology

A response surface methodology (RSM) was performed to study the influence of spot overlapping and pulse energy on back wall dross and surface roughness for fiber laser cutting of AISI 316 L stainless steel minitubes. Three treatments were compared to expel molten material (argon gas, compressed air, and a control test). Our results indicated that back wall dross and dross height reduction is observed when argon gas or compressed air is used through tubes compared with the control test. Additionally, a higher value of spot overlap (87.49%) and a lower value of pulse energy (30.31 mJ) resulted as the optimal parameters to cut minitubes.

2.79-μm high peak power LiNbO3 acousto-optic Q-switched Er,Cr:YSGG laser with thermal lensing effect compensation

A new type of lithium niobate (LiNbO3) acousto-optic Q-switched Er,Cr:YSGG laser with high peak power was designed and the thermal lensing effect compensation was studied. The values of thermal focal length in the gain medium were calculated theoretically and measured experimentally. The experimental results validate the designed plane-convex resonator validity, and the output performance of the 2.79 μm Er,Cr:YSGG laser was obviously improved. When the laser operated at free running region, the maximum values of pulse energy was 160 mJ at 60 Hz, compared with the plane-parallel resonator, the pulse energy was increased by 2 times in the plane-convex resonator. When the LiNbO3 Q-switched laser operated at 60 Hz, the maximum values of pulse energy was 8.5 mJ, and the minimum values of pulse duration was 60.8 ns, and the corresponding peak power approximately was 140 kW, respectively. Compared with the plane-parallel resonator, the pulse energy was increased by 1.6 times in the plane-convex resonator, the corresponding peak power was increased by 2.3 times.

Modified Mach-Zehnder interferometer for spatial coherence measurement.

Spatial coherence of light sources is usually obtained by using the classical Young's interferometer. Although the original experiment was improved upon in successive works, some drawbacks still remain. For example, several pairs of points must be used to obtain the complex coherence degree (normalized first-order correlation function) of the source. In this work, a modified Mach-Zehnder interferometer which includes a pair of lenses and is able to measure the spatial coherence degree is presented. With this modified Mach-Zehnder interferometer, it is possible to measure the full 4D spatial coherence function by displacing the incoming beam laterally. To test it, we have measured only a 2D projection (zero shear) of the 4D spatial coherence, which is enough to characterize some types of sources. The setup has no movable parts, making it robust and portable. To test it, the two-dimensional spatial coherence of a high-speed laser with two cavities was measured for different pulse energy values. We observe from the experimental measurements that the complex degree of coherence changes with the selected output energy. Both laser cavities seem to have similar complex coherence degrees for the maximum energy, although it is not symmetrical. Thus, this analysis will allow us to determine the best configuration of the double-cavity laser for interferometric applications. Furthermore, the proposed approach can be applied to any other light sources.

Прямая фемтосекундная лазерная запись двулучепреломляющих структур с высоким пропусканием в плавленом кварце

The writing process of birefringent structures in the volume of fused silica by focused ultrashort laser pulses with wavelength in visible range and various values of pulse energy, pulse duration, repetition rate, numerical aperture and moving substrate velocity has been studied. The retardance value of fabricated structures has been measured and influence of the subsequent annealing of these structures has been studied. It was shown, that combination of writing layered structures with subsequent annealing provides structures with high homogeneity, required retardance value and high transmittance.

The morphological and compositional changes of bimetallic Ti/Al thin film induced by ultra-short laser pulses

Results regarding morphological and compositional changes of bimetallic thin film (BMTF), composed of aluminium (Al) and titanium (Ti) nano-layers, by single fs laser pulses, are presented. Laser irradiation was conducted in the air with focused, linearly polarized laser pulses, the duration being 300 fs, wavelength 515 nm, and pulse energy up to 1.2~upmu hbox {J}. Effects of the variations of the pulse energy on the changes were studied. In the experiment, single pulse energy values from 0.03 to 0.08 upmu hbox {J} caused ablation–photomechanical spallation of the upper part of BMTF layer from the Si substrate, without ablation of the whole film. Irradiation at higher pulse energies gradually removed the whole BMTF and even a part of the Si substrate. We explained the influence of different electron–phonon dynamics, in the case of multilayered thin films composed of Al and Ti, on BMTF ablation. Damage/ablation threshold, which is minimal pulse energy/fluence sufficient for starting ablation, was calculated.Graphic abstract

Improvement of spectral responsivity of ZnO nanoparticles deposited on porous silicon via laser ablation in liquid

In the present study, synthesis and characterization of Zinc Oxide (ZnO) nano-particles with the pulsed laser ablation (PLD), from a zinc metal target in methanol at a variety of the laser pulse energy values 400, 600 and 800 mJ with 200 shots and 1064 nm laser wavelength. Porous silicon (PS) layers were prepared from n-type silicon with orientation (100) by photo-electrochemical etching (PECE) method. The morphological properties of ZnO NPs deposited on PS presented a good adhesion between these nanostructures leading to improve the structural stability of the PS substrate. UV–vis–NIR spectrophotometer, X-ray diffraction (XRD), electrical characteristics and Photodetector are utilized for the characterization of the products. So the detector measurements of ZnO NPs/PS exhibited a higher responsivity (0.04 A/W).

CHARACTERIZATION OF TITANIUM LASER WELDS

Butt welding of commercially pure titanium Grade 1 and Ti6Al4V alloy sheets using a pulsed Nd:YAG laser KLS 246 - 102 LASAG were carried out to determine optimal values of pulse energy and pulse length to create completely penetrated weld. Surface peak power density of about 3.105 W.cm−2 was found as an optimal value. Weld dimensions, both face width and penetration depth, are found to be proportional to increasing energy and decreasing pulse length. Gentle sagging and root penetration were revealed by means of contact surface profilometry. The nanohardness tests on transverse cross-sections detected approximately 50% higher hardness in the fusion zone than in the base material.

Microwave antenna properties of an optically triggered superconducting ring

We examine the microwave radiation emitted from inductively charged centimeter-scale YBCO (YBa2Cu3O7-δ) annular rings illuminated with a 45 fs, 790 nm laser pulse. The electromagnetic radiation from the rings shows the following behavior. (1) Radiation emitted perpendicular to the plane of the ring is polarized parallel to the plane of the ring and across the point of illumination. (2) The in-plane radiation pattern resembles that of a loop antenna with the orientation of the pattern determined by the location of the illumination point. (3) The dominant frequency of the emitted radiation shows an inverse dependence on the ring diameter. (4) The emitted energy is proportional to energy stored in the ring for a number of different geometries, with thinner films displaying a higher efficiency. Finally, (5) the emitted energy grows exponentially with small laser pulse energy values and approaches saturation for higher energies. These results indicate that optically induced electromagnetic radiation from superconducting structures holds promise for a versatile, compact, self-contained superconducting microwave emitter platform.

Giant Nonlinear AlGaAs-Doped Glass Photonic Crystal Fibers for Efficient Soliton Generation at Femtojoule Energy

In this paper, a unique semiconductor-doped glass photonic crystal fiber has been designed, which is suitable for soliton propagation at femto-Joule energy. The fiber promises to yield low and uniform anomalous dispersion profile and very large optical nonlinearities $\text{25 211 W}^{ - 1} {\text{km}}^{ - 1}$ at telecommunication wavelength, and, thus, facilitating soliton formation at ultralow energy. The observed magnitude of nonlinearity is the highest reported ever till date in AlGaAs-doped glass. The soliton dynamics has been investigated taking into account of higher order dispersions and nonlinearities. Propagating solitons breadth and experience large frequency shift, this decrease with the increase in the initial pulse width and increase with the increase in pulse energy. Temporal width of solitons oscillates, the frequency and amplitude of oscillations increase with the increase in the value of pulse energy.

Propagation of ultrashort resonant ionizing laser pulses in rubidium vapor

We investigate the propagation of ultra-short laser pulses in atomic rubidium vapor. The pulses are intensive enough to ionize the atoms and are directly resonant with the 780 nm $D_2$ line. We derive a relatively simple theory for computing the nonlinear optical response of atoms and investigate the competing effects of strong resonant nonlinearity and ionization in the medium using computer simulations. A nonlinear self-channeling of pulse energy is found to produce a continuous plasma channel with complete ionization. We evaluate the length, width and homogeneity of the resulting plasma channel for various values of pulse energy and initial focusing to identify regimes optimal for applications in plasma-wave accelerator devices such as that being built by the AWAKE collaboration at CERN. Similarities and differences with laser pulse filamentation in atmospheric gases are discussed.

Analytical estimations of pulse parameters in the modified integral neutron kinetics model for pulsed reactor and subcritical block

Application of modified integral neutron kinetic model to calculate principal characteristics of pulsed coupled reactor system consisting of pulsed reactor and subcritical block is discussed. The model is based on the use of respective time-dependent kernels of integral equation for reactor power and space-time Green's function for the subcritical block. It is possible to reduce the set of integral equations to the set of elementary algebraic and first-order differential equations by using exponential approximation of the kernels and Green's function.Approximations of «inertialess» reactivity dumping and jump reactivity boost on prompt neutrons are used as the «reactivity-power» feedback in order to close the mathematical model. This allows integrating corresponding kinetic equations in analytical form notwithstanding the fact that the kinetic equation for reactor is nonlinear.Analytical relations allowing estimating basic characteristics of the system such as energy and maximum pulse power in the reactor and in the subcritical block with accuracy sufficient in engineering practices were obtained.The performed calculations showed applicability of the analytical dependences of energy characteristics of the system on the impact coefficient of subcritical block on the reactor, on the lifetime of neutrons in the reactor and on the «time» constant of the block for fixed value of pulse energy in the reactor. The obtained ratio is valid for the reactor within the whole range of variation of system parameters while for the subcritical block it is correct only for the system operated with fast neutron spectrum in the reactor and with thermal neutron spectrum in the subcritical block when the so-called “delta” approximation of the reactor pulse is realized. In the case when such approximation is not valid the “Gaussian” approximation to the shape of the reactor pulse is applied for which more accurate analytical formulas were also obtained for estimation of maximum pulse energy in the block. These formulas depend on the ratio of duration of start-up period of the pulsed coupled reactor system to the value of “time” constant of the subcritical block and are correct for the systems with similar neutron spectra.The obtained analytical relations can be applied for optimization of parameters of coupled reactor-laser systems.

임신오조 환자의 맥파 분석 예비 연구

ABSTRACT A Pilot Study on Pulse Energy Measured by 3D Blood Pressure Pulse Analyzer in Women with Mild Hyperemesis GravidarumJu-Eun Bae, Young-Jin YoonDept. of Korean OB & GY, School of Korean Medicine,Pu-San National UniversityObjectives: The purpose of this study was to analyze the characteristics o f the pulse energy in women who complained mild hyperemesis gravidarum.Methods: We analyzed the values of pulse energy on 14 patients who suff ered mild hyperemesis gravidarum. The patients' symptoms were assessed by PUQE (Pregnancy-Unique Quantification of Emesis scale). Statistical analysis was perfo rmed using SPSS 18.0 for window program, one way ANOVA, pearson correlation coeffici ent.Results: The results were as follows.1. There were no statistically s ignificant pulse energy differe nces.2. The Chon pulse energy showed negative correlations with each Kwan and Cheok.3. PUQE score showed positive correlations with right Chon puls e energy and negative correlations with right Kwan pulse energy.Conclusions: The result suggested that PUQE score changes be positive relat ed with spleen pulse energy and negative related with lung pulse e nergy.Key Words: Hyperemesis, PUQE index, Pulse energy, Pulse diagnosis

Fabrication and application of zirconia-erbium doped fibers

In this work, the fabrication of a Zirconia-Erbium co-Doped Fiber (Zr-EDF) and its application in the generation of non-linear effects as well as use in a compact pulsed fiber laser system is described. The Zr-EDF is fabricated by the Modified Chemical Vapor Deposition (MCVD) technique in combination with solution doping to incorporate the glass modifiers and nucleating agent. The resulting preforms are annealed and drawn into fiber strands with a 125.0 ± 0.5 µm diameter. Two Zr-EDFs, ZEr-A and ZEr-B, are fabricated with erbium ion concentrations of 2800 and 3888 ppm/wt and absorption rates of 14.5 and 18.3 dB/m at 980 nm respectively. Due to its higher erbium dopant concentration, a 4 m long ZEr-B is used to demonstrate the generation of the Four-Wave-Mixing (FWM) effect in the Zr-EDF. The measured FWM power levels agree well with theoretical predictions, giving a maximum FWM power - 45 dBm between 1558 nm to 1565 nm, and the generated sidebands are as predicted. The non-linear coefficient of ZEr-B is measured to be 14 W−1km−1, with chromatic and slope dispersion values of 28.45 ps/nm.km and 3.63 ps/nm2.km respectively. The ZEr-B is also used together with a graphene based saturable absorber to create a compact, passively Q-switched fiber laser. Short pulses with a pulse width of 8.8 µs and repetition rate of 9.15 kHz are generated at a pump power of 121.8 mW, with a maximum average output power of 161.35 µW and maximum pulse energy value of 17.64 nJ. The fabricated Zr-EDF has many potential applications in multi-wavelength generation as well as in the development of compact, pulsed laser sources.

Generation of InN nanocrystals in organic solution through laser ablation of high pressure chemical vapor deposition-grown InN thin film

We report the synthesis of colloidal InN nanocrystals (InN-NCs) in organic solution through nanosecond pulsed laser ablation of high pressure chemical vapor deposition-grown InN thin film on GaN/sapphire template substrate. The size, the structural, the optical, and the chemical characteristics of InN-NCs demonstrate that the colloidal InN crystalline nanostructures in ethanol are synthesized with spherical shape within 5.9–25.3, 5.45–34.8, 3.24–36 nm particle-size distributions, increasing the pulse energy value. The colloidal InN-NCs solutions present strong absorption edge tailoring from NIR region to UV region.

Optical Properties of Femtosecond Laser-Synthesized Silicon Nanoparticles in Deionized Water

Silicon nanoparticles were prepared by ultrafast laser ablation of a silicon target in deionized water. The nanoparticles were characterized by using optical absorption, Raman spectroscopy, and transmission electron microscopy. The mean size is found to vary from 60 to 2.5 nm in the absence of any reducing chemical reagents, decreasing the pulse energy value. High-resolution transmission electron microscopy together with Raman spectroscopy confirms the crystalline structure of the generated silicon nanoparticles. The energy confinement of carriers which is evaluated from optical experiments varies from 90 to 550 meV when the mean nanoparticles size decreases from 60 to 2.5 nm. In particular, the evaluated nanoparticle sizes from optical analysis and the LCAO theoretical model are found in agreement with transmission electron microscopy and Raman measurements for the silicon nanoparticles with a size less than 6 nm. Finally, we present stability studies which show that the smallest nanoparticles aggregate ...

Generation of 1.5–12 ns width-tunable 532 nm pulses by adopting laser-induced plasma shutter technique

The pulse-shaping technique has found widespread applications in nonlinear optics and material processing. Experimental research on laser-induced plasma shutter to control the 532 nm pulse width is conducted. The impacts of the total pulse output energy on pulse compression are investigated, and a useful conclusion can be drawn that there exists an optimal value of pulse energy at which the shortest output pulse of 3.23 ns can be obtained without a device for delay-time. Once the device for delay-time is employed to change the optical differences between two laser paths, the pulse width can be further shortened to 1.51 ns. In short, the 1.5–12 ns width-tunable 532 nm laser pulses have been obtained by adopting the laser-induced plasma shutter technique.

Theoretical investigations of the processes of selective laser interaction with melanin granules in pigmented tissues for laser applications in medicine

Theoretical investigations and the results of computer modeling of optical, thermophysical, thermochemical, and hydrodynamical processes during selective laser interaction with melanoprotein granules (melanosomes) in heterogeneous pigmented tissues (retinal pigment epithelium) are reviewed in this paper. Physico-mathematical models and system of equations are formulated which describe interaction processes for “short” laser pulses of duration t p < 10−6 s and for “long” pulses of duration t p > 10−6 s. The results of numerical simulation of the processes give the space-time distributions of temperature and degrees of thermodenaturation of the protein molecules inside and around melanosomes and in the volume of irradiated tissue. Energy absorption, heat transfer, and thermochemical processes occurring during the interaction of laser pulses with pigmented spherical and spheroidal granules in heterogeneous tissues are theoretically investigated. The possibility for selective interaction of short laser pulses with pigmented granules, which results in the formation of denaturation microregions inside and near the pigmented granules (granular thermodenaturation) without origination of a continuous macroscopic thermodenaturation lesion in tissue, is discussed. An analytical model of heating of a single spherical and spheroidal granule by a laser pulse is presented. Simple equations for the time dependences of particle temperature are obtained. Vapor generation under the action of a laser pulse on pigmented spherical granules in a water-containing tissue and the formation and dynamics of a vapor blanket are theoretically investigated. The values of pulse energy which give rise to granular and ophthalmoscopically visible thermodenaturation lesions on the retina and to vapor generation are discussed, as well as laser-induced breakdown on granules in pigmented tissues, on the basis of experimental results and numerical and analytical calculations. The comparison and agreement of the numerical results with the experimental data validate the models and techniques developed. The presented results are of essential interest for laser applications in ophthalmology and can be used to investigate laser interaction with heterogeneous tissues in dermatology and various fields of laser medicine.