Shortest Pulse Width Research Articles

Diode-pumped Dy[formula omitted], Tb[formula omitted]:LuLiF[formula omitted] continuous-wave and passively Q-switched yellow lasers

We report on the power-scaling continuous-wave (cw) Dy3+, Tb3+:LuLiF 4 yellow laser, which comprises a single-emitter blue laser diode (LD) that functions as a pump source. The maximum output power of the laser is evaluated to be 220 mW at 574 nm. The passively Q-switched yellow laser is generated by using Cr4＋:Y3Al5O12 (Cr:YAG) as the saturable absorber. The shortest pulse width (full width at half maximum) is less than 582 ns with a repetition rate of 5.8 kHz. Meanwhile, the pulse energy and peak power are ∼4.5 μJ and ∼7.7 W, respectively. This work reveals that Dy3+, Tb3+:LuLiF 4 crystal is a potential laser gain material that can be used to develop compact and efficient yellow lasers, which can not only be employed in cw lasers but also in passively Q-switched pulse lasers.

Ultralow‐Power Synaptic Transistors Based on Ta2O5/Al2O3 Bilayer Dielectric for Algebraic Arithmetic

AbstractMultifarious artificial synaptic devices are extensively proposed in the field of neuromorphic hardware systems for their applicability in promising parallel computer architecture, which is preferred to classical Von Neumann architecture in numerous and complex information processing. Besides the ability to mimic typical biological synaptic behaviors, low power consumption is critical for the synaptic devices in the neuromorphic hardware system.In this paper, ultralow‐power Ta2O5/Al2O3 bilayer‐gate‐dielectric synaptic transistors (TABSTs) with low‐temperature atomic layer deposited dielectric are proposed. The TABSTs show power consumption as low as 19.9 aJ per synaptic event successfully at a low drain voltage of 0.001 V and a short pulse width of 1 ms. Essential synaptic behaviors including excitatory postsynaptic current, inhibitory postsynaptic current, spike‐amplitude‐dependent plasticity, spike‐duration‐dependent plasticity, paired pulse facilitation, long‐term potentiation, long‐term depression, the transition from short‐term memory to long‐term memory as well as learning and forgetting abilities are well mimicked by the TABSTs. Moreover, algebraic arithmetic operations such as addition, subtraction, multiplication, and division are also implemented by the TABSTs. This work provides a promising approach to emerging neuromorphic systems.

Effect of femtosecond pulse profile on excitation and dissociation of the nonadiabatic coupling molecule

The dependences of the excitation and dissociation of NaI induced by a pump–probe femtosecond laser field on the pulse profile are theoretically studied. When the pulse profile is varied, the oscillation period and amplitude of wave packets remain constant, but excitation and dissociation change. The effect of pulse profiles on branching ratio decreases for long pulse widths. There is no dissociation in the far-off resonant region. The excitation and dissociation of molecules can be effectively selected by adjusting pulse profiles in the resonant region and short pulse width. These novel results are important for the molecular spectroscopy and optical control.

High-power and high-efficiency 4.3 µm ZGP-OPO

In this paper, a high-power and high-efficiency 4.3 µm mid-infrared (MIR) optical parametric oscillator (OPO) based on ZnGeP2 (ZGP) crystal is demonstrated. An acousto-optically Q-switched Ho:Y3Al5O12 laser operating at 2.1 µm with a maximum average output power of 35 W and pulse width of 38 ns at a repetition rate of 15 kHz is established and employed as the pump source. A doubly resonant OPO is designed and realized with the total MIR output power of 13.27 W, including the signal and idler output power of 2.65 W at 4.07 µm and 10.62 W at 4.3 µm. The corresponding total optical-to-optical and slope efficiencies are 37.9% and 67.1%, respectively. The shortest pulse width, beam quality factor, and output power instability are measured to be 36 ns, Mx2=1.8, My2=2.0, and RMS<1.9% at 8 h, respectively. Our results pave a way for designing high-power and high-efficiency 4–5 µm MIR laser sources.

β-Ga2O3 Used as a Saturable Sbsorber to Realize Passively Q-Switched Laser Output

β-Ga2O3 crystals have attracted great attention in the fields of photonics and photoelectronics because of their ultrawide band gap and high thermal conductivity. Here, a pure β-Ga2O3 crystal was successfully grown by the optical floating zone (OFZ) method, and was used as a saturable absorber to realize a passively Q-switched all-solid-state 1 μm laser for the first time. By placing the as-grown β-Ga2O3 crystal into the resonator of the Nd:GYAP solid-state laser, Q-switched pulses at the center wavelength of 1080.4 nm are generated under a output coupling of 10%. The maximum output power is 191.5 mW, while the shortest pulse width is 606.54 ns, and the maximum repetition frequency is 344.06 kHz. The maximum pulse energy and peak power are 0.567 μJ and 0.93 W, respectively. Our experimental results show that the β-Ga2O3 crystal has great potential in the development of an all-solid-state 1 μm pulsed laser.

Thermal lens Q-switched 1064 nm Nd:YAG laser

We report a 1064 nm Nd:YAG solid-state laser Q-switched by the dynamic thermal lens effect. The feasibility of using the thermal lens effect to realize Q-switch was proved based on the theoretical analysis of the dynamic thermal lens effect and the simulation of the Q-switched rate equation. Further, a thermal lens Q-switched experimental device with an 808 nm pumped Nd:YAG laser was constructed. The output laser beams with a repetition rate of 100 Hz, pulse width of 15.02 ns, single pulse energy of 11.9 mJ, and working wavelength of 1064 nm were realized by thermal lens Q-switch under the pump power of 412 W and pump pulse width of 80μs. The beam quality factors of the output pulse in x and y directions were 2.63 and 2.94, respectively. The results demonstrate that using a thermal lens Q-switch can generate laser beams with high energy and short pulse widths.

The effect of carboxymethylcellulose host concentration on the performance of mode-locked pulsed laser generation

In this work, the effect of changing the polymer host concentration of a film-based saturable absorber (SA) on the performance of a mode-lock laser in an erbium-doped fiber (EDF) ring cavity was demonstrated. Carboxymethylcellulose (CMC) and graphene oxide (GO) films were used as the polymer host and SA respectively with the CMC-GO films being prepared by the solution casting technique. Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM) analysis showed increased interaction taking place between the polymer host and the SA material as the concentration of the polymer host was increased. X-ray diffraction (XRD) analysis reveals the formation of SA aggregation. Elements in the CMC-GO films were verified using energy dispersive X-ray (EDX) analysis. The modulation depth for 3 mg/mL of CMC and 5 mg/mL of CMC were 4.9% and 4.3%, respectively. Mode-locked pulse operation using 5 mg/mL has a shorter pulse width and broader 3 dB bandwidth than 3 mg/mL. The peak power and pulse energy of 5 mg/mL mode-locked operation were higher than 3 mg/mL. The film with 5 mg/mL shows better stability which was confirmed by the signal-to-noise ratio results.

The dynamic characteristics of pure-quartic solitons and soliton molecules

Pure-quartic solitons (PQSs) with higher energy in short pulse width have been generated in the mode-locked fiber laser recently, and soliton molecules have been found as a means to improve the communication capacity of the optical fiber, which has attracted much attention. In this paper, we consider the fourth-order nonlinear Schrödinger equation (FNLSE) derived from Lakshmanan-Porsezian-Daniel equation which is describing the propagation of PQS in optical fiber systems. Through the Hirota’s bilinear method, the bilinear forms and the one- and two-PQS solutions of the FNLSE are obtained. Then, the dynamic characteristics of the PQSs are discussed by using parameter control. Besides, through the velocity resonance conditions, the static and non-static PQS molecules are obtained. Under the condition of different parameters, the dynamic characteristics of the PQS molecules transmission process are analyzed. An interesting phenomenon of the PQS molecular interaction is found. We find that under the certain conditions, the PQS molecule composed of two solitons can evolve into the stable new form. Moreover, the soliton-asymmetric soliton molecule are obtained by the parameters control.

반도체 스위치 기반 고전압 펄스전원 연구 동향

This paper describes the research trends of the high voltage pulsed power modulator based on semiconductor switch. The research on the solid-state pulsed power modulator technology can be classified into three topics that were performed for introducing the topology of pulsed power modulator to overcome the ratings of semiconductor device, increasing the rated power with long pulse width and low voltage droop, minimizing rising/falling time with short pulse width. This paper provides a brief overview of these three research topics and introduces the developed pulsed power modulator in Korea Electrotechnoloy Institute(KERI).

Stem/Proliferative and Differentiated Cells within Primary Murine Colonic Epithelium Display Distinct Intracellular Free Ca2+ Signal Codes.

The second messenger, intracellular free calcium (Ca2+ ), acts to transduce mitogenic and differentiation signals incoming to the colonic epithelium. A self-renewing monolayer of primary murine colonic epithelial cells is formed over a soft, transparent hydrogel matrix for the scalable analysis of intracellular Ca2+ transients. Cultures that are enriched for stem/proliferative cells exhibit repetitive, high frequency (≈25 peaks h-1 ), and short pulse width (≈25 s) Ca2+ transients. Upon cell differentiation the transient frequency declines by 50% and pulse width widens by 200%. Metabolites and growth factors that are known to modulate stem cell proliferation and differentiation through Wnt and Notch signaling pathways, including CHIR-99021, N-[(3,5-Difluorophenyl)acetyl]-L-alanyl-2-phenylglycine-1,1-dimethylethyl ester (DAPT), bone morphogenetic proteins (BMPs), and butyrate, also modulate Ca2+ oscillation patterns in a consistent manner. Increasing the stiffness of the supportive matrix from 200 Pa to 3 GPa shifts Ca2+ transient patterns toward those resembling differentiated cells. The ability to monitor Ca2+ oscillations with the spatial and temporal resolution offered by this platform, combined with its amenability to high-content screens, provides a powerful tool for investigating real-time communication within a wide range of primary tissues in addition to the colonic epithelium.

Ternary 2D Mo(1-x)WxS2 as a saturable absorber for femtosecond mode-locked all fiber lasers

In this paper, we utilized the ternary Mo(1-x)WxS2 alloys to fabricate Mo0.5W0.5S2 film, which serve as a ultrashort pulse mode-locker in erbium-doped all fiber lasers (EDFL). The modulation depth, saturable intensity and unsaturated loss of the film SA were 12%, 4.5 MW/cm2 and 67.1% respectively. Stable self-mode-locking pulses could be achieved with a threshold pump power of 60 mW. With the increasing pump power, the pulse was centered at 1556.8 nm ~ 1558.1 nm with pulse width of 575 fs ~ 800 fs. The shortest pulse width, fundamental repetition rate and maximum pulse energy is 575 fs, 4.873 MHz, and 0.154 nJ, respectively. The signal to noise ratio (SNR) was measured to be about 53 dB. For the first time, we have experimentally demonstrated a mode-locked EDFL based on Mo0.5W0.5S2 SA. To the best of our knowledge, this was the first realization of femtosecond photonics based on Mo0.5W0.5S2 SAs. Our results suggest that Mo0.5W0.5S2 SA is a promising candidate for mode-locked ultrafast fiber laser in optoelectronic and optical communications applications.

PD06-07 EFFECT OF PULSE WIDTH VARIATIONS ON SACRAL NEUROMODULATION FOR OVERACTIVE BLADDER SYMPTOMS: A PROSPECTIVE RANDOMIZED CROSSOVER PILOT STUDY

You have accessJournal of UrologyUrodynamics/Lower Urinary Tract Dysfunction/Female Pelvic Medicine: Female Incontinence: Therapy I (PD06)1 Sep 2021PD06-07 EFFECT OF PULSE WIDTH VARIATIONS ON SACRAL NEUROMODULATION FOR OVERACTIVE BLADDER SYMPTOMS: A PROSPECTIVE RANDOMIZED CROSSOVER PILOT STUDY Jessica Rueb, Howard Goldman, Sandip Vasavada, Courtenay Moore, Raymond Rackley, and Bradley Gill Jessica RuebJessica Rueb More articles by this author , Howard GoldmanHoward Goldman More articles by this author , Sandip VasavadaSandip Vasavada More articles by this author , Courtenay MooreCourtenay Moore More articles by this author , Raymond RackleyRaymond Rackley More articles by this author , and Bradley GillBradley Gill More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000001974.07AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: The pulse width (PW) parameter in sacral neuromodulation (SNM) is understudied, with no evidence-based guidance available on alternative PW for bladder indications. The aim of this prospective, randomized, single-blinded, 3x3 cross over design study was to estimate the effect of two PW settings (60 ms, 420 ms) compared to the industry standard (210ms) on efficacy, quality of life, and device parameters. METHODS: Eligible patients had urge incontinence or urgency-frequency and subjectively satisfied at the time of enrollment. Patients completed a 3-day voiding diary, validated questionnaires, and device interrogations at baseline and after each 4 week period on the three settings. Eighteen subjects completed the study. RESULTS: Mean age was 68 years, and mean implant duration was 4.4 years. PW variations did not result in a significant difference in regards to overall objective outcomes. In regards to device parameters amplitude and change in battery life were significantly different with alternative PW. (Table 1) A shortened PW required an average higher amplitude (4.10 vs 2.10) while saving battery life (2.35 months). Subjective stimulus sensation such as location, quality, and intensity did not differ between PW. 11 patients chose standard PW after the study, 5 chose extended, and 2 chose shortened. Upon subset analysis for those that chose an alternative PW, change in urinary frequency from enrollment was significantly different, with an average reduction of -2.23 (p=0.015). For those patients who reported doing “much better” or “very much better” on the extended PW, they reported significantly less urinary frequency and nocturia at 5.6 and 0.4, compared to 8.5 and 2.16 (p=0.005, p=<0.001.) For those patients who reported doing “much better” or “very much better” on the shortened PW, they reported significantly less urinary frequency at 5.15 compared to 7.35 (p=0.026). CONCLUSIONS: In this prospective cross over trial overall device effectiveness was unchanged through use of alternative PW, however 39% of patients preferred an alternative PW with measurable change noted. Our findings support prior animal model data that a shorter PW can result in the same efficacy while saving estimated battery life. Source of Funding: SUFU Foundation Study of Neuromodulation Research Grant © 2021 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 206Issue Supplement 3September 2021Page: e102-e102 Advertisement Copyright & Permissions© 2021 by American Urological Association Education and Research, Inc.MetricsAuthor Information Jessica Rueb More articles by this author Howard Goldman More articles by this author Sandip Vasavada More articles by this author Courtenay Moore More articles by this author Raymond Rackley More articles by this author Bradley Gill More articles by this author Expand All Advertisement Loading ...

Generation of nanosecond pulsed azimuthally and radially polarized beams with an actively Q-switched rotating disk laser

We have directly generated two kinds of vector polarized beam pulses from an end pumped rotating Nd:YAG disk laser design acousto-optic Q-switch pulse modulation. About 20 ns pulse width with peak power 29 kW and stable pulse vector polarized beams are achieved at the continuous absorbed pump power. The laser crystal rotary effectively alleviates thermal effect that affects the power scaling with high beam quality. The output state is controlled by an intra-cavity polarization selector birefringent crystal. The polarization degrees of the azimuthally and radially polarized beams are 98.6% and 98.2%, respectively. The study suggests that this new method would constitute a laser light source for producing power and single pulse energy scaling, short pulse width, and high-purity structured vector beams and serve this function.

MXene Ti3C2T x thin film as a saturable absorber for passively mode-locked and Q-switched fibre laser

We have experimentally demonstrated the mode-locked and Q-switched fibre lasers based on MXene Ti3C2T x as a saturable absorber (SA). MXene Ti3C2T x was obtained using selective etching and then embedded into polyvinyl alcohol (PVA) to form the thin film. A stable soliton mode-locked laser was achieved when the Ti3C2T x film was added in the Erbium-doped fibre laser cavity, and the pump power was adjusted between 55 and 144 mW. The pulse width of mode-locked laser was obtained to be 3.68 ps, while the repetition rate was 1.89 MHz. The maximum average output power and pulse energy were measured to be 24.42 mW and 12.92 nJ. After we decreased the cavity length by removing 100 m of SMF, the same SA could produce Q-switched laser instead of mode-locked laser. The Q-switched laser operated within the pump power of 19–66 mW, having the shortest pulse width and operating wavelength of 2.6 µs and 1557 nm, respectively.

Geometry calibration and image reconstruction for carbon-nanotube-based multisource and multidetector CT

Conventional intraoperative computed tomography (CT) has a long scan time, degrading the image quality. Its large size limits the position of a surgeon during surgery. Therefore, this study proposes a CT system comprising of eight carbon-nanotube (CNT)-based x-ray sources and 16 detector modules to solve these limitations. Gantry only requires 45° of rotation to acquire the whole projection, reducing the scan time to 1/8 compared to the full rotation. Moreover, the volume and scan time of the system can be significantly reduced using CNT sources with a small volume and short pulse width and placing a heavy and large high-voltage generator outside the gantry. We divided the proposed system into eight subsystems and sequentially devised a geometry calibration method for each subsystem. Accordingly, a calibration phantom consisting of four polytetrafluoroethylene beads, each with 15 mm diameter, was designed. The geometry calibration parameters were estimated by minimizing the difference between the measured bead projection and the forward projection of the formulated subsystem. By reflecting the estimated geometry calibration parameters, the projection data were obtained via rebinning to be used in the filtered-backprojection reconstruction. The proposed calibration and reconstruction methods were validated by computer simulations and real experiments. Additionally, the accuracy of the geometry calibration method was examined by computer simulation. Furthermore, we validated the improved quality of the reconstructed image through the mean-squared error (MSE), structure similarity (SSIM), and visual inspections for both the simulated and experimental data. The results show that the calibrated images, reconstructed by reflecting the calibration results, have smaller MSE and higher SSIM values than the uncalibrated images. The calibrated images were observed to have fewer artifacts than the uncalibrated images in visual inspection, demonstrating that the proposed calibration and reconstruction methods effectively reduce artifacts caused by geometry misalignments.

Linearity and Nonlinearity in Hollow-Core Antiresonant Fiber Sensors in the Terahertz Regime

In nonlinear optics, a major challenge is to maximize the interaction between the light from laser sources and low-density media such as gases. An ultrafast laser beam can be focused to form a highly intense spot over a small concentrated area. The ultrafast laser beam has a short pulse width of less than one picosecond and high peak power in the beam profile (Fig. 1). The beam profile of the laser source describes the energy density and distribution of light, and the beam profile of a laser source is usually affected during the propagation and collimation of the beam. An efficient nonlinear optical sensor also requires high peak power at low energy (low average power) over short duration of laser pulse, a high beam profile and long interaction length. These requirements of a nonlinear optical sensor with low attenuation constant can be achieved in hollow-core photonic crystal fiber (HC-PCF). Gas-filled HC-PCF exhibits optical nonlinearity for an ultrashort temporal and spectral broadening of NIR pulses [1], [2]. The nonlinearity in HC-PCF can be achieved by tuning the gas pressure. Gas-filled HC-PCF nonlinear media are low-cost, replenishable, reconfigurable and exhibit sharp spectral lines [3]. Linear and nonlinear responses are also found in other types of optical fibers.

Spark discharges in liquid heptane in contact with silver nitrate solution: Investigation of the synthesized particles

AbstractIn this study, spark discharges are generated in liquid heptane that is in contact with an immiscible solution of silver nitrate. The results demonstrate that the discharges produced at 22 kV voltage amplitude and 500 ns pulse width change the color of both liquids and lead to the formation of nanoparticles. Most particles collected from heptane are nanocomposites of Ag nanoparticles (&lt;10 nm) in the hydrocarbon network. Meanwhile, the material collected from the silver nitrate solution is Ag nanoparticles (10–150 nm of diameter). At shorter pulse width (100 ns), the discharges generate similar materials in both liquids; however, the size distribution of these materials is smaller. Finally, a scenario of particle synthesis is proposed and discussed.

Effect of time and spatial domains on monolayer 2D material interface thermal conductance measurement using ns ET-Raman

Raman-based approaches to characterizing thermal properties of nanoscale and microscale materials have proven to be powerful experimental methods. This work explores the potential of energy-transport state-resolved Raman (ET-Raman) for the precise determination of interfacial thermal conductance (G) between monolayer 2D materials and their substrates. ET-Raman employs a continuous wave laser and nanosecond (ns) pulsed laser to induce both steady state and transient heating while simultaneously collecting 2D material temperature information from the Raman signal. A 3D numerical model built using the finite volume method simulates the two differentiated thermal transport processes. The simulated temperature rises are compared with experimental Raman temperature information to extract G. In this study, we investigate the temporal effects of the pulse frequency and pulse width of the ns laser on precise characterization of G. By running multiple simulations for a range of pulsed laser frequencies and pulse widths, we determine that ET-Raman is most sensitive to precise interfacial thermal conductance measurements with short pulse widths (~below 20 ns) and with pulsing frequencies that ensure sufficient cooling time between consecutive pulses (~below 500 kHz). We also conclude that substrate thickness and laser spot size play critical roles in heat distribution and subsequent sensitivity to meaningful G measurements. As both laser spot size and SiO2 substrate thickness decrease, detection of interfacial thermal transport becomes more difficult. These results offer essential guidance in the design of future Raman-based approaches to thermal measurements using pulsed lasers.

Deep brain stimulation fine-tuning in Parkinson's disease: Short pulse width effect on speech

Backgroundsubthalamic nucleus deep brain stimulation (STN-DBS) may have a detrimental effect on speech in Parkinson's disease (PD) patients and new stimulation technologies may help in addressing this issue. Objectiveto evaluate the STN-DBS acute effect of 30 μs pulse width (30PW) versus conventional 60 μs PW (60PW) on speech and identify the core features of voice modified by 30PW. Methodsseven STN-DBS treated PD patients participated into a pilot cross-sectional study. Motor and speech performances were tested by means of both automatic analysis and blinded clinical evaluations in four stimulation conditions: 30PW and 60PW both at the usual amplitude and at an amplitude just below the threshold for stimulation-related side effects. Resultsat the threshold amplitude, 30PW stimulation improved speech intelligibility for both words (p = 0.02) and sentences (p = 0.04), without worsening motor performance. A lower but not statistically significant voice variability and instability and percentage of stuttering disfluencies was also observed. The beneficial effect of 30PW detected by automatic analysis, was confirmed by patients’ perception. ConclusionsSTN-DBS treated patients experiencing low speech intelligibility may benefit from a 30PW stimulation trial at a higher amplitude. Deep characterization of PD speech profiles may help in a better application of recent DBS hardware advances.

Self-mode-locked alexandrite femtosecond lasers with multi-GHz repetition rates.

We report the laser-diode pumped multi-gigahertz (GHz) self-mode-locked alexandrite femtosecond (fs) lasers for the first time, to the best of our knowledge. Using a simple linear cavity, stable mode-locked laser was achieved with a repetition rate of 3.6 GHz and a pulse width of 237 fs. Additionally, the second-harmonic mode-locked pulse was realized with a repetition rate of 7.5 GHz and a pulse width of 201 fs based on the Fabry-Perot effect generated in the laser cavity. It was observed that this laser possesses advantages of high repetition rate and short pulse width that enable the development of promising applications in modern ultrafast photonics.