Pulse Generator Research Articles

An instrumentation amplifier with series switch pseudo resistor DC-servo loop realizing 0.16-Hz high-pass corner

This paper presents an instrumentation amplifier for electrocardiogram (ECG) signal recording. A DC servo loop (DSL) based on a series-switch pseudo resistor (S2PR ) is utilized to suppress the effect of the unavoidable electrode DC offset effectively. The two-step pulse generation circuit realizes two sets of pulse signals with shallow duty cycles, and the pulse signals drive the path switches and virtual switches in the S2PR, respectively. Virtual switches reduce the channel charge injection effect, and finally, a great equivalent resistance with high linearity is realized. The continuous DSL realized based on S2PR can suppress the electrode DC offset of ±180 mV. At the same time, the active area of the DSL is significantly reduced. The proposed instrumentation amplifier is realized in a standard 0.18-μm CMOS process. Simulation results show the DSL designed with a 1.8-V supply introduces a 0.16-Hz high-pass corner. The power consumption of the S2PR-DSL is 92.7 μW. The gain of the instrumentation amplifier is 39.8 dB, and the input-referred noise at the TT corner is 1.78 μVrms over a bandwidth of 0.5 Hz to 150 Hz. The input impedance of the instrumentation amplifier is 772.2 MΩ, when the input signal frequency is 50 Hz, and the total harmonic distortion (THD) of a 10-mVpp input sinusoidal signal at 9.033 Hz is −61.6 dB.

Assessment of the effectiveness of high-pressure water jet machining generated using self-excited pulsating heads

The article presents the research findings on the process of machining with a pulsating water jet. The study determined the influence of water velocity and pressure, providing insights into the dynamics of pulsating water jets. An evaluation of the generation process of pulsating water jets was conducted for various models of self-excited pulsating heads. The aim was to determine the impact of geometric parameters of the self-excited pulsating head and hydrodynamic working conditions on the performance of such a head, the dynamic characteristics of the water jet it produces, and its technological suitability for material erosion. In the first stage, simulation studies were carried out for three models of self-excited pulsating heads. Based on these studies, a solution with appropriate geometry was selected. Subsequently, experimental studies were conducted using the self-excited head and dedicated research setups. For the selected solution of the self-excited pulsating head, pulse durations, jet thrust forces, and frequency variations for different working pressure values were determined. The analysis showed a correlation between the geometric parameters of the head, pressure changes, and the characteristics of the generated pulses in the pulsed water jets. Pulse generation was made possible by increasing the water flow through side openings. Pulses with greater water volume exhibited increased erosive potential, particularly noticeable at higher pressures. It was found that pressure changes also affect the pulse frequency, with shorter intervals observed at lower pressures and longer intervals at higher pressures. The results presented in the paper highlight the importance of tool geometry and changes in water pressure at the inlet to the self-excited pulsating heads and the dynamics of the pulsed water jet. Research on the pulse generation mechanism and the assessment of erosive potential can form the basis for optimizing the design and operation of pulsating water jets in surface machining. This comprehensive understanding underpins the enhancement of efficiency and effectiveness of pulsating water jet applications in various industrial and manufacturing processes.

Tunable high energy pulse generation in the range of 2.9-3.6 μm enabled by an actively Q switched Er3+/Dy3+ codoped fluoride fiber oscillator.

We demonstrate, for the first time, an actively Q switched red-diode-clad-pumped Er3+/Dy3+ codoped fluoride fiber oscillator. Its wavelength can be continuously tuned over the range of 2.906-3.604 μm (698 nm), representing the widest tuning span of pulsed fluoride fiber oscillators in the mid-infrared. In addition, the achieved pulse energy at each wavelength of >2.95 μm is also higher than that of a previously reported pulsed fluoride fiber oscillator at the corresponding wavelength, to the best of our knowledge. By tuning the wavelength to 3.204 μm, the highest pulse energy of 82 μJ has been gotten with a pulse width of 520 ns at a repetition rate of 500 Hz.

Generation of dual-wavelength Q-switched pulses and bright-dark pulses pairs in an erbium-doped fiber laser with NbS2 as saturable absorber

In this experiment, stable dual-wavelength Q-switched pulses and bright-dark pulses pairs are achieved in an erbium-doped fiber laser based on NbS2 under saturable absorber. At pump powers of 172 mW–322 mW, stable dual-wavelength Q-switched pulses with center wavelengths of 1531.9 nm and 1557.05 nm were obtained with a signal-to-noise ratio (SNR) as high as 43 dB. The repetition frequency was increased from 14.3 kHz to 22.7 kHz as the pump power was increased. When the pump power was increased to 340 mW, we found stable bright-dark pulses with center wavelengths of 1559.7 nm and 1560.12 nm, respectively, and a repetition frequency of 3.44 MHz with an SNR of 52 dB. The experimental results show that NbS2 can be used as an excellent SA for fiber lasers and demonstrate that NbS2 can be used to study dual-wave Q-switched pulses and bright-dark soliton pairs.

Motor improvement of remote programming in patients with Parkinson's disease after deep brain stimulation: a 1-year follow-up.

Remote programming (RP) is an emerging technology that enables the adjustment of implantable pulse generators (IPGs) via the Internet for people with Parkinson's disease (PwPD) who have undergone deep brain stimulation (DBS). Previous studies have not comprehensively explored the effectiveness of RP in managing motor symptoms, often omitting assessments such as the rigidity and retropulsion tests during the follow-up. This study evaluates the comprehensive improvements in motor performance and the potential cost benefits of RP for PwPD with DBS. A retrospective analysis was conducted on two groups of patients-those who received RP and those who received standard programming (SP). Clinical outcomes including motor improvement, quality of life, and daily levodopa dosage were compared between the groups during a 12 (± 3)-month in-clinic follow-up. A total of 44 patients were included in the study, with 18 in the RP group and 26 in the SP group. No significant differences were observed in the frequency of programming sessions or clinical outcomes between the groups (p > 0.05). However, the RP group experienced significantly lower costs per programming session than the SP group (p < 0.05), despite patients in the former group living further from our center (p < 0.05). Our findings suggest that RP could significantly reduce the costs of programming for PwPD with DBS, especially without compromising the effectiveness of treatment across all motor symptoms in the short term.

POMC neurons control fertility through differential signaling of MC4R in Kisspeptin neurons.

Inactivating mutations in the melanocortin 4 receptor ( MC4R ) gene cause monogenic obesity. Interestingly, female patients also display various degrees of reproductive disorders, in line with the subfertile phenotype of MC4RKO female mice. However, the cellular mechanisms by which MC4R regulates reproduction are unknown. Kiss1 neurons directly stimulate gonadotropin-releasing hormone (GnRH) release through two distinct populations; the Kiss1 ARH neurons, controlling GnRH pulses, and the sexually dimorphic Kiss1 AVPV/PeN neurons controlling the preovulatory LH surge. Here, we show that Mc4r expressed in Kiss1 neurons is required for fertility in females. In vivo , deletion of Mc4r from Kiss1 neurons in female mice replicates the reproductive impairments of MC4RKO mice without inducing obesity. Conversely, reinsertion of Mc4r in Kiss1 neurons of MC4R null mice restores estrous cyclicity and LH pulsatility without reducing their obese phenotype. In vitro , we dissect the specific action of MC4R on Kiss1 ARH vs Kiss1 AVPV/PeN neurons and show that MC4R activation excites Kiss1 ARH neurons through direct synaptic actions. In contrast, Kiss1 AVPV/PeN neurons are normally inhibited by MC4R activation except under elevated estradiol levels, thus facilitating the activation of Kiss1 AVPV/PeN neurons to induce the LH surge driving ovulation in females. Our findings demonstrate that POMC ARH neurons acting through MC4R, directly regulate reproductive function in females by stimulating the "pulse generator" activity of Kiss1 ARH neurons and restricting the activation of Kiss1 AVPV/PeN neurons to the time of the estradiol-dependent LH surge, and thus unveil a novel pathway of the metabolic regulation of fertility by the melanocortin system.

Full phonon dispersion along the stacking direction in nanoscale van der Waals materials by picosecond acoustics

Phonon dispersion in crystals determines many important material properties, but its measurement usually requires large-scale facilities and is limited to bulk samples. Here, we demonstrate the measurement of full phonon dispersion along the stacking direction in nanoscale systems by using picosecond acoustics. A heterostructure sample was prepared consisting of layers of hexagonal boron nitride (hBN) sandwiching a thin layer of black phosphorus (BP), within which a strain pulse was generated by photoexcitation and observed with an optical probe in the BP layer. The strain pulse traverses to the few nanometer thick hBN layers, where it propagates to the edge and echoes back, like acoustic waves in Newton’s cradle. The echoes returning to the BP layer provide information on the frequency-dependent time-of-flight and group velocity dispersion of the sample system. The microscopic origin of the photoinduced strain pulse generation and its propagation is revealed from first principles. Phonon frequency combs observed in the Fourier transform spectrum confirm the strain wave round trips and demonstrate the feasibility of determining group velocity dispersion through photoacoustics.

Molybdenum gallium carbide coated D-shape fiber for nanosecond dark pulse generation in erbium-doped fiber laser

Molybdenum gallium carbide (Mo2Ga2C), a material belongs to MAX phase group, has garnered significant interest in a wide range of scientific field, including material science, engineering, and laser physics. It is chemically and structurally promising since it exhibits a low shear modulus, superconducting behaviour, and high mechanical stability. Here, we prepared a saturable absorber (SA) based on Mo2Ga2C coated D-shape fiber using solution casting technique. It exhibits outstanding saturable absorption of 7.2%, allowing it to generate dark pulse laser in an erbium-doped fiber laser cavity. We analyzed the laser’s performance and obtained a dark pulse with a pulse energy, peak power, and average output power of 3.9 nJ, 27.5 mW, and 7.3 mW, respectively. This foundational work may introduce a new material as an alternative SA device in fiber laser cavity.

Rates and Predictors of Pain Reduction With Intracranial Stimulation for Intractable Pain Disorders.

Intracranial modulation paradigms, namely deep brain stimulation (DBS) and motor cortex stimulation (MCS), have been used to treat intractable pain disorders. However, treatment efficacy remains heterogeneous, and factors associated with pain reduction are not completely understood. We performed an individual patient review of pain outcomes (visual analog scale, quality-of-life measures, complications, pulse generator implant rate, cessation of stimulation) after implantation of DBS or MCS devices. We evaluated 663 patients from 36 study groups and stratified outcomes by pain etiology and implantation targets. Included studies comprised primarily retrospective cohort studies. MCS patients had a similar externalized trial success rate compared with DBS patients (86% vs 81%; P = .16), whereas patients with peripheral pain had a higher trial success rate compared with patients with central pain (88% vs 79%; P = .004). Complication rates were similar for MCS and DBS patients (12% vs 15%; P = .79). Patients with peripheral pain had lower likelihood of device cessation compared with those with central pain (5.7% vs 10%; P = .03). Of all implanted patients, mean pain reduction at last follow-up was 45.8% (95% CI: 40.3-51.2) with a 31.2% (95% CI: 12.4-50.1) improvement in quality of life. No difference was seen between MCS patients (43.8%; 95% CI: 36.7-58.2) and DBS patients (48.6%; 95% CI: 39.2-58) or central (41.5%; 95% CI: 34.8-48.2) and peripheral (46.7%; 95% CI: 38.9-54.5) etiologies. Multivariate analysis identified the anterior cingulate cortex target to be associated with worse pain reduction, while postherpetic neuralgia was a positive prognostic factor. Both DBS and MCS have similar efficacy and complication rates in the treatment of intractable pain. Patients with central pain disorders tended to have lower trial success and higher rates of device cessation. Additional prognostic factors include anterior cingulate cortex targeting and postherpetic neuralgia diagnosis. These findings underscore intracranial neurostimulation as an important modality for treatment of intractable pain disorders.

Experimental and numerical study of different mode-locking techniques in holmium fiber laser with a ring cavity

Experimental and numerical study has been performed for three techniques of mode-locking in all-fiber Holmium laser. We have compared the fundamental repetition rate pulsed generation for mode-locking based on: nonlinear polarization evolution, polymer-free single-walled carbon nanotubes, and hybrid mode-locking. Experimental and numerical simulation results demonstrated the shortest pulse duration and maximum spectrum width for mode-locking based on the nonlinear polarization evolution: 1.3 ps, 4.2 nm and 1.3 ps, 4.1 nm, respectively. The self-starting mode in this case can vary depending on external conditions in the experiment. In Ho-doped fiber laser with polymer-free single-walled carbon nanotubes mode-locking, the small modulation depth of saturable absorption leads to a long time period of stationary single-pulse lasing development (about 104 cavity roundtrips in simulation, and ≈5 s in the experiment). Both experimental and numerical studies have indicated that a Ho-doped fiber laser with hybrid mode-locking provides optimal generation, enabling self-starting and a relatively fast transition to stable single-pulse lasing (less than 1.5 × 103 cavity roundtrips in simulation, and ≈3 s in experiment). This study presents the first employment of polymer-free single-walled carbon nanotubes for hybrid mode-locking in a Ho-doped fiber laser.

Second-harmonic generation of ultrashort pulses in refractive index linearly modulating quantum dot structure

While other works use segments of nonlinear crystal to compensate for walk-off, this work utilizes a quantum dot (QD) nanostructure for such compensation. Such nanocrystal structures allow two benefits: the high nonlinear susceptibility in these nanocrystals and the high surface density of QDs in the structure. Good results are obtained for pre-chirping and modulation parameters. The results are computed at 10 and 100 kV/cm applied electric fields. Compared to ordinary nonlinear crystals, the pulse width, intensity, and efficiency of the second harmonic (SH) pulse are all higher in QD nanocrystals, even with a low electric field applied. Higher applied fields give higher results.

Generation of attosecond gigawatt soft x-ray pulses through coherent Thomson backscattering.

Collision between relativistic electron sheets and counterpropagating laser pulses is recognized as a promising way to produce intense attosecond x rays through coherent Thomson backscattering (TBS). In a double-layer scheme, the electrons in an ultrathin solid foil are first pushed out by an intense laser driver and then interact with the laser reflected off a second foil to form a high-density relativistic electron sheet with vanishing transverse momentum. However, the repulsion between these concentrated electrons can increase the thickness of the layer, reducing both its density and subsequently the coherent TBS. Here, we present a systematic study on the evolution of the flying electron layer and find that its resulting thickness is determined by the interplay between the intrinsic space-charge expansion and the velocity compression induced by the drive laser. How the laser driver, the target areal density, the reflector, and the collision laser intensity affect the properties of the produced x rays is explored. Multidimensional particle-in-cell simulations indicate that employing this scheme in the nonlinear regime has the potential to stably produce soft x rays with several gigawatt peak power in hundreds of terawatt ultrafast laser facilities. The pulse duration can be tuned to tens of attoseconds. This compact and intense attosecond x-ray source may have broad applications in attosecond science.

Generation of double attosecond pulses with the same intensity and carrier-envelope phase

Generation of double attosecond pulses with the same intensity and carrier-envelope phase

Fundamental frequency switching strategies of a seven level hybrid cascaded H-bridge multilevel inverter

This paper presents a novel hybrid cascaded H-bridge multilevel inverter (HCHB MLI) designed to address the growing importance of multilevel inverters in the context of renewable energy sources such as solar, wind, and fuel cells. The proposed topology features eight insulated-gate bipolar transistor (IGBT) switches and utilizes two distinct input direct current (DC) sources: a battery and a capacitor, making it a hybrid system. The control strategy employed in this topology is based on fundamental switching frequency techniques. Simulation results of the proposed topology are conducted using MATLAB/Simulink software, while hardware experimentation with a single-phase H-bridge inverter is also demonstrated in the paper. For pulse generation and IGBT switch control, an Arduino UNO microcontroller is utilized. The output voltage of the single-phase H-bridge inverter is verified through experimentation using a cathode-ray oscilloscope (CRO).

Preliminary analysis of stimulation parameters for sacral neuromodulation in different indications: A multi-center retrospective cohort study from China.

Sacral neuromodulation (SNM) is an effective approach for treating lower urinary tract dysfunction (LUTD), and stimulation programming is essential for successful treatment. However, research on SNM programming for various indications is limited. Thus, we aimed to determine whether there were differences in the stimulation parameters for different SNM indications and the appropriate programming recommendations. Clinical data were retrospectively collected from patients with LUTD who underwent SNM and completed internal pulse generator (IPG) implantation. The parameters with the highest patient satisfaction or the most symptom improvement during the test period were considered optimal and used to set the programming after IPG implantation. After screening, 282 patients were enrolled and categorized into four groups based on the following indications: refractory overactive bladder (OAB) (n=61), neurogenic lower urinary tract dysfunction (nLUTD) (n=162), interstitial cystitis/painful bladder syndrome (IC/BPS) (n=24), and idiopathic non-obstructive urinary retention (NOUR) (n=35). When analyzing the optimal stimulus parameters, disparities in the stimulation amplitude and pulse frequency were noted among the four groups. The stimulation amplitude in the nLUTD group was higher than that in the idiopathic NOUR group (P=0.013). Differences in pulse frequency were observed between the refractory OAB and nLUTD groups (P<0.001) and between the refractory OAB and idiopathic NOUR groups (P=0.001). No differences in the electrode configuration or pulse width settings existed among the four groups. The stimulation parameters for SNM varied among the different indications. For the initial programming of stage I, most patients are recommended to start with stimulation amplitudes below 2 V, although patients with nLUTD may benefit from higher amplitudes. A standard pulse width of 210μs is recommended for all patients. However, for individuals experiencing nLUTD or idiopathic NOUR, the pulse frequency can begin above the standard 14Hz but not exceed 50Hz.

Burst-mode pulse generation in passively mode-locked all-fiber green/orange lasers at 543 nm and 602 nm

We report on the experimental realization of, to the best of our knowledge, the first green and orange passively mode-locked all-fiber lasers. Stable mode-locking in the burst-pulse status is achieved at the wavelengths of 543.3 nm and 602.5 nm. The figure-9 cavity comprises the fiber end-facet mirror, gain fiber (Ho3+:ZBLAN fiber or Pr3+/Yb3+:ZBLAN fiber), and fiber loop mirror (FLM). The FLM with long 460 HP fiber is not only used as an output mirror, but also acts as a nonlinear optical loop mirror for initiating visible-wavelength mode-locking. The green/orange mode-locked fiber lasers with the fundamental repetition rates of 3.779/5.662 MHz produce long bursts containing ultrashort pulses with the 0.85/0.76 GHz intra-burst repetition rates, respectively. The ultrashort intra-burst pulses stem from the dissipative four-wave-mixing effect in the highly nonlinear FLM as well as the intracavity Fabry–Perot filtering. Long bursts of 22.2/11.6 ns with ultrashort pulses of 87/62 ps are obtained in our experiment. The visible-wavelength passively mode-locked lasers in an all-fiber configuration and burst-mode would represent an important step towards miniaturized ultrafast fiber lasers and may contribute to the applications in ablation-cooling micromachining, biomedicine imaging, and scientific research.

Clinical study of a micro-implantable pulse generator for the treatment of peripheral neuropathic pain: 3-month and 6-month results from the COMFORT-randomised controlled trial

BackgroundWe report the results from the first large, postmarket, multicentre, randomised controlled trial (RCT) evaluating peripheral nerve stimulation (PNS) for the treatment of chronic peripheral pain with a micro-implantable pulse...

Q-Switched Pulse Generation in Erbium-based with Niobium Aluminium Carbide Saturable Absorber

Q-Switched Pulse Generation in Erbium-based with Niobium Aluminium Carbide Saturable Absorber

Transverse mode switchable mode-locked laser with narrow bandwidth

Transverse mode switchable ultrashort optical pulses with narrow bandwidths can create potential for exploring what we believe are new physical effects. We demonstrate the generation of transverse mode switchable ultrashort pulses with narrow bandwidths in an all-fiber mode-locked laser by exploring a mode-selective photonic lantern (MSPL). The laser cavity serves not only as a ring resonator but also as an intrinsic spectral filter. For mode-locking with the LP01, LP11a, and LP11b modes, the bandwidths are 3.0 nm, 86.7 pm and 101.7 pm, respectively. The narrowband pulses with higher-order modes are generated by an intrinsic spectral filter due to the spectral-domain intermodal interference. Mode-locked pulses with a signal-to-noise ratio better than 60 dB for LP01, LP11a, and LP11b modes are independently generated, i.e., transverse mode switchable by changing the input port of the MSPL. The mode-locked wavelength can be tuned for the LP11a mode and LP11b mode by adjusting the state of polarization. Furthermore, our experimental results also show that, the slope efficiency of LP11a and LP11b modes can be improved, by the use of LP11 mode pump scheme. We anticipate that, narrowband pulses with complex mode profiles can be generated by simultaneously phase-locked transverse and longitudinal modes.

Efficient (∼10%) generation of vacuum ultraviolet femtosecond pulses via four-wave mixing in hollow-core fibers.

We report the generation of the fifth harmonic of Ti:sapphire, at 160 nm, with more than 4 µJ of pulse energy and a pulse length of 37 fs with a 1 kHz repetition rate. The vacuum ultraviolet pulses are produced using four-wave difference frequency mixing in a He-filled stretched hollow-core fiber, driven by a pump at 267 nm and seeded at 800 nm. Guided by simulations using Luna.jl, we are able to optimize the process carefully. The result is a conversion efficiency of ∼10% from the 267 nm pump beam.