Longer Pulse Width Research Articles

Temperature profiles of low-temperature alloy irradiated by pulsed ion beams

While alloy materials is irradiated by the high-intensity pulsed ion beams (HIPIB), the temperature distributions surrounding the primary heated regions used numerical analysis has been studied extensively over the past few years. Compared with the temperature distributions induced by HIPIB, few information is known about the temperature distributions on alloy materials used in practice as it is irradiated by the pulsed ion beams which possess characteristics of lower energy density and longer pulse width. The main reason is that the interaction between the alloy materials and the pulsed ion beams is only a few microseconds. It is difficult to detect temperature changes on alloy materials used in practice through traditional test. Ablation, melting, defects of microstructure on alloy materials are always used to validate the results of numerical analysis about the temperature distributions indirectly. In order to evaluate the temperature distributions directly, the dynamic thermal-dependent temperature behavior of the low-temperature alloy irradiated by the pulsed ion beams is investigated by experimental observation and finite element method (FEM) simulation in this paper. The temperature profiles generated from the interaction of μs-size between the alloy materials and the pulsed ion beams are evaluated by coupling characteristics of the low melting point and the pulsed ion beams. The FEM simulation results of the maximum temperature agree well with the experimental results on the surface of the low-temperature alloy. Results gained show that the maximum temperature on the surface of the low-temperature alloy irradiated by the pulsed ion beams can be applied to deduce the maximum temperature on alloy materials used in practice.

Range separation performance and optimal pulse-width prediction of a three-dimensional flash laser detection and ranging using the Cramer–Rao bound

This paper derives the Cramer-Rao bound (CRB) on range separation estimation of two point sources interrogated by a three-dimensional flash laser detection and ranging (LADAR) system. An unbiased range separation estimator is also derived to compare against the bound. Additionally, the CRB can be expressed as a function of two LADAR design parameters (range sampling and transmitted pulse width), which can be selected in order to optimize the expected range resolution between two point sources. Given several range sampling capabilities, the CRB and simulation show agreement that there is an optimal pulse width where a shorter pulse width would increase estimation variance due to undersampling of the pulse and a longer pulse width would degrade the resolving capability. Finally, the optimal pulse-width concept is extended to more complex targets and a normalized pulse definition.

Second Stokes 1129 nm generation in gray-trace resistance KTP intracavity driven by a diode-pumped Q-switched Nd:YVO4 laser

A gray-trace resistance KTP (GTR-KTP) second Stokes Raman laser intracavity driven by a diode-pumped acousto-optic Q-switched Nd:YVO4 laser was first demonstrated in this paper. With an incident pump power of 9.5 W, the intracavity GTR-KTP Raman laser, operating at the repetition rate of 20 kHz, produced the maximum average output power of 860 mW at 1129 nm. The minimum pulse width obtained in this GTR-KTP Raman laser was 10.8 ns. When the GTR-KTP was substituted with a common KTP, a lower average output power of 720 mW and longer pulse width of 15.9 ns were obtained in the common KTP Raman laser under the same pump condition and cavity setup as the GTR-KTP Raman laser. Experimental results indicated that the decreased absorption at the fundamental and Stokes wave in GTR-KTP was beneficial to improve the stimulated Raman scattering performance.

Efficient GTR-KTP IOPO driven by a diode-pumped Nd:YAG/Cr4+:YAG laser with the shared cavity configuration

An efficient eye-safe GTR-KTP IOPO with the shared cavity configuration and excited by a diode-end-pumped composite Nd:YAG/Cr4+:YAG laser was demonstrated. Under the incident LD power of 8.4 W, the maximum average output power of 900 mW at 1572 nm was obtained with the T=33% output coupler, corresponding to a diode-to-signal conversion efficiency of 10.7%. The corresponding signal pulse width and repetition rate were respectively 2.2 ns and 12 kHz, with the peak power and single pulse energy estimated to be 34.1 kW and 75 µJ, respectively. The instability of the average signal output power over hours-long operation was found to be 2.0%. As for the common KTP IOPO at the same pump condition and cavity design, a lower average output power of 640 mW with a longer pulse width of 4.6 ns was obtained. The corresponding diode-to-signal conversion efficiency was reduced by 28.8% compared with that obtained in GTR-KTP IOPO. A theoretical model for the compact GTR-KTP IOPO was also presented in this paper. Theoretical analysis on the pulse characteristics of the signal was performed, which showed a good agreement with that obtained experimentally.

Transient Characteristics of the Reset Programming of a Phase-Change Line Cell and the Effect of the Reset Parameters on the Obtained State

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In this paper, we investigate the effect of the reset-pulse parameters of a phase-change memory line cell on the electrical cell properties. By means of electrothermal finite-element simulations and measurements, the characteristics of the reset state (resistance after switching, threshold voltage, and stability of the state) are related to the physical parameters during reset switching (the temporal and spatial distribution of the temperature during switching, the evolution of the melting and molten phases, and the time that the line is molten). From a device point of view, we emphasize the following aspects: 1) Due to good thermal isolation, the line cell can be reset using a 5-ns short current pulse of limited amplitude; 2) longer pulsewidths allow lower reset current amplitudes due to the gradual heating of surrounding dielectric; 3) the reset resistance has no direct relation with the threshold voltage but is strongly related to the number of reset pulses applied to the cell; and 4) shorter pulsewidths allow extended endurance lifetimes. </para>

Four-limb Neurostimulation with Neuroelectrodes Placed in the Lower Cervical Epidural Space

Four-limb Neurostimulation with Neuroelectrodes Placed in the Lower Cervical Epidural Space

Abstract P111: Applying the Principles of Functional Stimulation to Electrical CPR

Background: We have previously reported on a specialized electrical stimulus that produces coronary and carotid blood flow during VF. The values selected for the Current (C), Pulse Width (PW), Pulse Period (PP), Train Width (TW) and Train Rate (TR) are critical to obtaining effective blood flow. An initial experiment in which these parameters were systematically studied in order to identify the optimal parameters has been previously reported. In this study we utilized some of the principles established in the field of NeuroMuscular Electrical Stimulation (NMES) of the extremities to further optimize ECPR. A primary principle of interest is that the force produced is proportional to charge delivered (Coulombs or amp-seconds.) Consequently, higher C, longer PW, shorter PP and longer TW would be predicted to produce greater force. Hypothsis: We hypothesized that for ECPR as in NMES that: CPP over time would be proportional to the total charge delivered per constriction. Methods: We applied 118 episodes of ECPR in 7 porcine subjects as previously described. VF was electrically induced and untreated for 10 seconds. ECPR was then applied for 60 seconds or until CPP dropped below 15 mm Hg. The specific ECPR intervention applied was determined according to a factorial design of experiment in which two levels each of C, PW, PP and TW were evaluated. The CPP was recorded at 10-second intervals during ECPR until it was terminated. Results: PP and PW showed significant differences in their ability to maintain CPP &gt; 15 mm Hg (T15) for prolonged periods of time (PP=25 ms: 49±15 s to T15 vs PP=50 ms: 41±17 s to T15, p=0.004) (PW=0.2 ms: 42±17 s to T15 vs PW=0.8 ms: 48±16 s to T15, p=0.05). Regression analysis further showed that an increase in PW and a decrease in PP worked independently and without interaction to increase T15 for CPP. These two parameters relate directly to total charge delivered with the result that, for each additional unit of total charge delivered, there was an almost 8 times increase in the T15 time period (coefficient = 7.7, 95% CI=(6.5,8.9)) Conclusions: The increases in charge provided by longer PP and shorter PW produced significantly longer time of CPP &gt; 15 mm Hg within the limits of this test. Further study is required in order to further extend the duration of action ECPR.

Predicting Clinical Efficacy of Photoangiolytic and Cutting/Ablating Lasers using the Chick Chorioallantoic Membrane Model: Implications for Endoscopic Voice Surgery

The optimal balance between a laser's clinical efficacy and collateral thermal damage is the major determinant for selection of a particular laser in endolaryngeal surgery. The chick chorioallantoic membrane (CAM) simulates the microvasculature of the human vocal fold and is, therefore, useful for testing effects of laser settings, mode of delivery, active cooling, and wavelength. Such information is essential for optimizing the effectiveness of lasers in treating laryngeal pathology while preserving vocal function. The thermal and coagulative effects of four lasers (585 nm PDL, 532 nm KTP, 2.01ìm Thulium, 10.6ìm CO2) were quantified at selected (and clinically relevant) energy settings before and after tissue cooling using the CAM model. Measures included imaging real-time vascular reactions in the CAM model (i.e., vessel coagulation and/or rupture), and post-procedure histologic analysis of CAM tissue. In each experiment, laser energy was applied to the CAM in a controlled manner. Cooling was done using a dermatological cold-air device, and temperatures were measured with a thermistor. Lasers tested included the photoangiolytic pulsed-dye (PDL) and KTP, as well as the ablative/cutting CO2 and thulium lasers. The vessel rupture/coagulation and thermal effects of various energy-delivery parameters on the CAM, with and without cooling, were assessed. After removal of the CAM, specimens were stained as whole-mounts, photographed at 4X magnification, and evaluated by two independent, blinded surgeon reviewers. The efficacy of increased pulse-width (KTP laser) on treating larger vessels (>0.5 mm) and the effects of extravasated blood on photoangiolysis were also evaluated. Photoangiolytic lasers: Vessel coagulation/rupture rates showed that the PDL caused more frequent vessel rupture than the KTP laser. For both lasers, cooling the CAM by approximately 20 degrees C resulted in 30% - 60% reduction in the thermal-damage zone (P < .05). Cooling reduced the efficacy of coagulation with the PDL but not with the KTP laser. The clinically observed phenomenon that laser heating of extravasated blood increases thermal damage and decreases efficacy of coagulation was clearly evident in the CAM model. Ablative lasers: The thermal-damage zone of the CO2 laser (0.3 mm spot size) was not significantly different with or without cooling (0.32 mm2 and 0.34 mm2, respectively) (P = .30). However, when the spot size was defocused to 1 mm, the thermal-damage zone was over 2x greater when the tissue was not cooled (0.74 mm2 vs 0.35 mm2) (P < .002). The thermal-damage zone of the Thulium laser was reduced by an average of 58% for the three power settings tested when the CAM was air-cooled (P < .05). The CAM was an excellent model for studying the effects of photoangiolytic lasers, for which optimal pulse-widths exist for vessel coagulation. Smaller vessels coagulated reliably at pulse widths >15 msec, and larger vessels required pulse widths >35 msec for optimal coagulation. Cooling the target tissue decreased the thermal-damage zone created by photoangiolytic lasers. While cooling had no effect on the efficacy of coagulation with longer pulse widths (KTP), tissue cooling decreased the coagulation rate at shorter pulse widths (PDL). The thermal effects of cutting/ablating lasers can be reduced with cooling, but the CAM was not a good model with which to study coagulation/rupture rates in cutting/ablating lasers.

Bipolar high-repetition-rate high-voltage nanosecond pulser

The pulser designed is mainly used for producing corona plasma in waste water treatment system. Also its application in study of dielectric electrical properties will be discussed. The pulser consists of a variable dc power source for high-voltage supply, two graded capacitors for energy storage, and the rotating spark gap switch. The key part is the multielectrode rotating spark gap switch (MER-SGS), which can ensure wider range modulation of pulse repetition rate, longer pulse width, shorter pulse rise time, remarkable electrical field distortion, and greatly favors recovery of the gap insulation strength, insulation design, the life of the switch, etc. The voltage of the output pulses switched by the MER-SGS is in the order of 3-50 kV with pulse rise time of less than 10 ns and pulse repetition rate of 1-3 kHz. An energy of 1.25-125 J per pulse and an average power of up to 10-50 kW are attainable. The highest pulse repetition rate is determined by the driver motor revolution and the electrode number of MER-SGS. Even higher voltage and energy can be switched by adjusting the gas pressure or employing N(2) as the insulation gas or enlarging the size of MER-SGS to guarantee enough insulation level.

DEVELOPMENT OF SHIELDED REFLECTION TYPE PULSED EDDY CURRENT TESTING PROBES FOR THICKNESS EVALUATION

Reflection and send-receive type probe shielded by ferrite is designed to evaluate the thickness of test plate by a pulsed eddy current (PEC) method and effects of pulse width to PEC signal are investigated when a 10.5 mm thick, nonmagnetic plate is inspected. Results show that the best sensitivity to thickness variation can be achieved by the peak value of a PEC signal. Pulse width variation study suggests that the shorter pulse width is desired if the peak value or the zero crossing time is used to evaluate the thickness, while the longer pulse width is needed if the time to peak value is used to evaluate it.

Differences among implanted pulse generator waveforms cause variations in the neural response to deep brain stimulation

Objective Two different Medtronic implantable pulse generator (IPG) models are currently used in clinical applications of deep brain stimulation (DBS): Soletra and Kinetra. The goal of this study was to evaluate and compare the stimulation waveforms produced by each IPG model. Methods We recorded waveforms from a broad range of stimulation parameter settings in each IPG model, and compared them to idealized waveforms that adhered to the parameters specified in the programming device. We then used a previously published computational model to predict the neural response to the various stimulation waveforms. Results The stimulation waveforms produced by the IPGs differed from the idealized waveforms assumed in previous theoretical and clinical studies, and the waveforms differed among the IPG models. These differences were greater at higher frequencies and longer pulse widths, and caused variations of up to 0.4 V in activation thresholds for model axons located 3 mm from the DBS electrode contact. Conclusions The specific details of the stimulation waveform directly affect the neural response to DBS and should be accounted for in theoretical and experimental studies of DBS. Significance While the clinical selection of DBS parameters is individualized to each patient based on behavioral outcomes, scientific analysis of stimulation parameter settings and clinical threshold measurements are subject to a previously unrecognized source of error unless the actual waveforms produced by the IPG are accounted for.

Demonstration of Long-Pulse Power Amplification at 1 GHz Using 4H-SiC RF BJTs on a Conductive Substrate

In this letter, we report 4H-SiC RF bipolar junction transistors (BJTs) on an n-type 4H-SiC conductive substrate with, for the first time, RF power amplification at 1 GHz. The devices were fabricated using a double-mesa etch and interdigitated emitter-base finger design. When tested under common-base and pulsed Class AB mode at 1 GHz, the packaged devices with external matching exhibited a 10.1-dB power gain and a 22.9-W output power, with a 40.8% power-added efficiency (PAE) at 1-ms pulsewidth and 10% duty cycle. The RF power density is 313.8 W/cm2 , normalized to the total emitter finger area. At a longer pulsewidth of 6 ms and the same duty cycle of 10%, devices can still deliver a 16.2-W (222.2 W/cm2) output power, with 10-dB gain and 28.3% PAE. The RF performance combined with the lower cost SiC conductive substrate, as compared to the semi-insulating substrate, makes these devices promising for use in power amplifiers for long-pulse L-band radar applications

Effect of pulse width and fluence of femtosecond laser on the size of nanobump array

Conical nanobump arrays were generated on gold thin film processed by interfering femtosecond laser. The transition of the height and diameter as functions of fluence and pulse width was investigated. When the fluence was 87 mJ/cm 2, the height and diameter were not so different at 350 fs or shorter pulse width. They decreased at longer pulse width, and no bump could be generated over 1.6 ps. The results suggest the decrease of size is due to the diffusion of electron to not-excited region, and due to heat conduction to not heated region or substrate, or change of absorbance of laser. At long pulse width of 2.4 ps and relatively higher fluence of 190 mJ/cm 2, nanobump had liquid-like structure as a stop motion of a water drop.

Office-Based 532-nm Pulsed KTP Laser Treatment of Glottal Papillomatosis and Dysplasia

Treatment of glottal papillomatosis and dysplasia was mirror-guided and done in surgeons' offices in the 19th century. It migrated to the operating room in the 20th century to accommodate direct laryngoscopic surgery, which required assistants to administer anesthesia and procedural support. The primary treatment goals, which are disease regression and voice restoration and/or maintenance, are tempered by the morbidity of general anesthesia and potential treatment-induced vocal deterioration. To obviate general anesthesia, office-based laser laryngeal surgery was first done in 2001 with the 585-nm pulsed dye laser (PDL), because it employs a fiber delivery system and its energy is selectively absorbed by oxyhemoglobin. Since then, this new angiolytic laser treatment paradigm has become a mainstay of management for many surgeons; however, there are a number of shortcomings of the PDL. To further develop this concept and address the limitations of the PDL, we used a 532-nm pulsed potassium titanyl phosphate (KTP) laser. A prospective assessment was performed on 48 patients in 72 cases of recurrent glottal dysplasia (36) or papillomatosis (36). All individuals had previously undergone microlaryngoscopic management with histopathologic evaluation. Two dysplasia patients did not tolerate the procedure. Of the treatable dysplasia cases, there was follow-up in 29 of 34. Disease regression was at least 75% in 18 of 29 cases (62%), 50% to 75% in 7 of 29 (24%), and 25% to 50% in the remaining 4 of 29 (14%). Papilloma patients returned for treatment when symptoms recurred, so disease regression could not be assessed accurately. Similar to data obtained with the PDL, these data confirmed that dysplastic mucosa could normalize without resection. Our observations revealed that the 532-nm pulsed KTP laser provided enhanced performance over the PDL laser in a number of ways. The ability to use smaller glass fibers precluded mechanical trauma to the channels of the flexible laryngoscopes and allowed for improved suctioning of secretions. Oxyhemoglobin absorbs energy better at 532 nm than at 585 nm, and the KTP laser can be delivered through a longer pulse width. These factors provide enhanced hemostasis and improved intralesional energy absorbance. Finally, unlike the PDL, the KTP laser is a solid-state laser and is not prone to mechanical failure.

Pulsed Angiolytic Laser Treatment of Ectasias and Varices in Singers

Varices and ectasias in singers are typically the result of phonotraumatic shearing stresses and/or collision forces on the microcirculation within the superficial lamina propria. These lesions can be debilitating in performing vocalists because of the effect of recurrent hemorrhage and/or as a contributing factor to the morbidity of other mass lesions such as polyps, nodules, and cysts. Phonomicrosurgical treatment of performers is understandably approached with great trepidation, as the vocal liability of surgically disturbing the superficial lamina propria and epithelium must be balanced with the inherent detrimental vocal effect(s) of the lesion(s). Pulsed angiolytic lasers that emit radiation at high absorbance peaks of oxyhemoglobin were examined to determine whether they were an efficacious treatment approach for ectasias and varices based on these lasers' mechanisms of action and prior experience in phonomicrosurgery. A prospective trial was done in 39 patients (40 procedures in 54 vocal folds) without complication to evaluate the effectiveness of a 585-nm pulsed dye laser (PDL; 25 cases) and a 532-nm pulsed KTP laser (15 cases) in a noncontact mode to treat 65 varices and 43 ectasias. Twenty-nine of 39 patients had varices and ectasias associated with other phonotraumatic mass lesions that required resection. All patients have resumed full vocal activities, and no patient has had a subsequent hemorrhage or vocal deterioration. Both the 585-nm PDL and the 532-nm pulsed KTP laser were found to be efficacious and relatively safe treatment modalities for vascular abnormalities of the vocal folds in singers. Noncontact selective photoangiolysis of the aberrant vessels prevented future bleeding without substantial photothermal trauma to the overlying epithelium and surrounding delicate superficial lamina propria, thereby allowing for optimal postoperative mucosal pliability and glottal sound production. However, the pulsed KTP laser was substantially easier to use because of its enhanced hemostasis due to its longer pulse width. Vessel wall rupture was commonplace during use of the 585-nm PDL, but rarely occurred during photoangiolysis with the 532-nm pulsed KTP laser.

Communication between functional and denervated muscles using radiofrequency

This article focuses on establishing communication between a functional muscle and a denervated muscle using a radiofrequency communications link. The ultimate objective of the project is to restore the eye blink in patients with facial nerve paralysis. Two sets of experiments were conducted using the gastrocnemius leg muscles of Sprague-Dawley rats. In the initial tests, varying magnitudes of voltages ranging from 0.85 to 2.5 V were applied directly to a denervated muscle to determine the voltage required to produce visible contraction. The second set of experiments was then conducted to determine the voltage output from an in vivo muscle contraction that could be sensed and used to coordinate a signal for actuation of a muscle in a separate limb. After designing the appropriate external communication circuitry, a third experiment was performed to verify that a signal between a functional and a denervated muscle can be generated and used as a stimulus. Voltages below 2 V at a 10-millisecond pulse width elicited a gentle, controlled contraction of the denervated muscle in vivo. It was also observed that with longer pulse widths, higher stimulation voltages were required to produce sufficient contractions. It is possible to detect contraction of a muscle, use this to generate a signal to an external base station, and subsequently cause a separate, denervated muscle to contract in response to the signal. This demonstration in vivo of a signaling system for pacing of electrical stimulation of 1 muscle to spontaneous contraction of another, separate muscle, using radiofrequency communication without direct connection, may be used in numerous ways to overcome nerve damage.

Treatment homogeneity and conformal analysis of plasma based ion implanted 3D target

A prismoid-shaped target was treated by plasma based ion implantation (PBII) with nitrogen plasma, in order to study the lateral homogeneity in the near region of square corner after treatment. Auger electron spectroscopy was used to execute sputter depth profiling to obtain nitrogen depth distribution and retained dose on the silicon wafer. It showed that, in addition to process parameters of PBII such as pulse voltage, pulse width and radio frequency power, treatment homogeneity is strongly dependent on the shape and dimensions of the workpiece being treated. The ion retained dose and its gradient of distribution are a strong function of the factors mentioned above. Due to enhanced sputtering effect induced by the oblique ion impact, lower retained dose and shallower implantation depth were observed in the vicinity of the edge contained by square corner. The gradient of retained dose distribution exhibits a higher value with higher pulse voltage, lower plasma density, longer pulse width and smaller target size. Aided by the results of numerical simulation, sheath expanding tendency and ion impact mode under various conditions were discussed. Through conformal condition analysis of plasma sheath and the resulting characteristic of ion impingement, a better understanding of the treatment homogeneity can be achieved.

Experimental Study on a Condition of Rotating a Magnetic Ball by Applying the Pulse Magnetic Field

This paper describes a simulative experiment using a large scale model of a twisting ball magnetic display. One hemisphere of the magnetic ball with the diameter of 6mm is magnetized to &#x201C;North&#x201D; and colored white. The other hemisphere is magnetized to &#x201C;South&#x201D; and colored black. The electromagnet generates the pulse magnetic field to rotate the magnetic ball by applying the pulse current. As a half rotation is made, the visible color of the ball is inversed. Relationship between the pulse width and the amplitude of the current is studied. As the amplitude of the current is increased, the probability of rotation is increased. Finally the probability reaches 100%. As the pulse width is increased, the amplitude to rotate the ball is decreased. As a result, the following relationship is obtained. As the pulse width becomes one tenth, the correspondent amplitude for rotating the ball becomes double. For example, if the pulse width is 500ms, the correspondent amplitude is 0.3A. And as the pulse width is 50ms, the correspondent amplitude is 0.6A. This relationship is expressed by the following equation. In/I0 = (Tn/T0)&#x2212;log2, where In/I0 is the ratio of the amplitude compared with the initial amplitude and Tn/T0 is the ratio of the pulse width compared with the initial pulse width. It is also found that as the pulse width becomes one tenth, the correspondent electric energy becomes 0.4 times. This relationship is expressed by the following equation. Wn/W0 = (Tn/T0)&#x2212;log0.4 = (Tn/T0)log2.5, where Wn/W0 is the ratio of the electric energy. As a result it is found that a current with shorter width and higher amplitude is more effective than a current with longer pulse width and lower amplitude.

Use of a novel erbium laser in a Yucatan minipig: A study of residual thermal damage, ablation, and wound healing as a function of pulse duration†This article is a US Government work and, as such, is in the public domain in the United States of America.

Background and Objective Theoretical models show that varying pulse duration influences residual thermal damage in erbium YAG skin resurfacing. Accordingly, our objective was to compare residual thermal damage, ablation, tissue shrinkage, and wound healing between a variable pulsewidth erbium YAG laser and a popular CO2 resurfacing laser. Study Design/Materials and Methods The erbium laser delivered a typical ablative pulse (250 microseconds), followed by a heating pulse of variable duration. Pulse durations for specific coagulation depths were selected based on existing heat transfer models. The bilateral flanks of one Yucatan pig were irradiated. Eight sites were treated per group. Biopsies were performed just after treatment and 1, 3, 7, 21, and 60 days postoperatively. Results Just after irradiation, gross examination of “cold” (without a coagulation pulse) erbium sites showed a reddish papillary dermis consistent with conventional erbium laser ablation. Two and three pass CO2 sites showed uniform surface yellowing. The longer pulsewidth (“hot”) erbium groups showed only slight surface yellowing. Biopsies showed immediate thermal damage that increased with erbium pulse duration; however, actual residual thermal damage (RTD) was sometimes less than that predicted by the laser control panel. All wounds healed uneventfully by 14 days. Conclusions An erbium laser with a variable macropulse pulsewidth was capable of achieving RTD of up to 80 μm. Even greater RTD depths may be obtainable with future manipulations of fluence and pulse duration. Lasers Surg. Med. 30:93–100, 2002. © 2002 Wiley-Liss, Inc.

Optimum Effect of Asymmetric Laser Pulse Shape on Relativistic Laser-Plasma Wake Field

Effects of asymmetric laser pulse shapes with longer pulse width in falling than in rising on relativistic laser-plasma wake fields is studied. It is found that there exist an optimum pulse width ratio of in falling to in rising which excite the maximum magnitude of wake field potential. An approximate power law for this optimum ratio is obtained numerically.