Enhanced phase sensitivity in a Mach-Zehnder interferometer via photon recycling.

We propose an alternative scheme for phase estimation in a Mach-Zehnder interferometer (MZI) with photon recycling. It is demonstrated that with the same coherent-state input and homodyne detection, our proposal possesses a phase sensitivity beyond the traditional MZI. For instance, it can achieve an enhancement factor of ∼9.32 in the phase sensitivity compared with the conventional scheme even with a photon loss of 10% on the photon-recycled arm. From another point of view, the quantum Cramér-Rao bound (QCRB) is also investigated. It is found that our scheme is able to achieve a lower QCRB than the traditional one. Intriguingly, the QCRB of our scheme is dependent of the phase shift ϕ while the traditional scheme has a constant QCRB regardless of the phase shift. Finally, we present the underlying mechanisms behind the enhanced phase sensitivity. We believe that our results provide another angle from which to enhance the phase sensitivity in a MZI via photon recycling.

Comparative study of young-old and old-old people using functional evaluation, gait characteristics, and cardiopulmonary metabolic energy consumption.

BACKGROUND: Walking is an important factor in daily life. Among older adults, gait function declines with age. In contrast to the many studies revealing gait differences between young adults and older adults, few studies have further divided older adults into groups. The purpose of this study was to subdivide an older adult population by age to identify age-related differences in functional evaluation, gait characteristics and cardiopulmonary metabolic energy consumption while walking. METHODS: This was a cross-sectional study of 62 old adult participants who were classified into two age groups of 31 participants each as follows: young-old (65-74 years) and old-old (75-84 years) group. Physical functions, activities of daily living, mood state, cognitive function, quality of life, and fall efficacy were evaluated using the Short Physical Performance Battery (SPPB), Four-square Step Test (FSST), Timed Up and Go Test (TUG), Korean Version of the Modified Barthel Index, Geriatric Depression Scale (GDS), Korean Mini-mental State Examination, EuroQol-5 Dimensions (EQ-5D) questionnaire, and the Korean version of the Fall Efficacy Scale. A three-dimensional motion capture system (Kestrel Digital RealTime System®; Motion Analysis Corporation, Santa Rosa, CA, USA) and two force plates (TF-4060-B; Tec Gihan, Kyoto, Japan) were used to investigate spatiotemporal gait parameters (velocity, cadence, stride length, stride width, step length, single support, stance phase, and swing phase), kinematic variables (hip, knee, and ankle joint angles), and kinetic variables (hip, knee, and ankle joint moment and power) of gait. A portable cardiopulmonary metabolic system (K5; Cosmed, Rome, Italy) was used to measure cardiopulmonary energy consumption. RESULTS: The old-old group showed significantly lower SPPB, FSST, TUG, GDS-SF, and EQ-5D scores (p < 0.05). Among spatiotemporal gait parameters, velocity, stride length, and step length were significantly lower in the old-old group than in the young-old group (p < 0.05). Among the kinematic variables, the knee joint flexion angles during initial contact and terminal swing phase were significantly higher in the old-old than the young-old group (P < 0.05). The old-old group also showed a significantly lower ankle joint plantarflexion angle during the pre- and initial swing phases (P < 0.05). Among the kinetic variables, the hip joint flexion moment and knee joint absorption power in the pre-swing phase were significantly lower in the old-old than the young-old group (P < 0.05). CONCLUSION: This study demonstrated that participants 75-84 years of age had less functional gaits than their young-old counterparts (65-74 years old). As the walking pace of old-old people diminishes, driving strength to move ahead and pressure on the knee joint also tend to decrease together with stride length. These differences in gait characteristics according to age among older adults could improve our understanding of how aging causes variations in gait that increase the risk of falls. Older adults of different ages may require customized intervention plans, such as gait training methods, to prevent age-related falls. TRIAL REGISTRATION: Clinical trials registration information: ClinicalTrials.gov Identifier: NCT04723927 (26/01/2021).

Effect of 4-weeks exercise program using wearable hip-assist robot (EX1) in older adults: one group pre- and post- test.

BACKGROUND: Older adults have muscle loss and are at risk of falling. Recently, research in the healthcare field has been actively conducted, and Samsung Electronics has developed EX1, a hip joint assisted robot for exercise. This study aimed to verify the effect of a 4-week combined exercise program applying EX1 on older adults. METHODS: This study design was an evaluator-blinded, pre- and post-test. A total of 21 older adults performed an exercise program consisting of walking and fitness wearing EX1 for 50 min per session, 3 days a week during the 4-week exercise period. For comparison before and after participating in the exercise program, the spatio-temporal parameters, pelvic movement were analyzed by G-Walk, functional outcomes were evaluated by TUG, muscle power were evaluated by RUSI, and waist-hip ratio were analyzed by Inbody. All data were analyzed before and after exercise using paired t-test, and the statistical significance level was set at 0.05. RESULTS: In spatio-temporal parameters, stride length showed statistically significant improvements after exercise with EX1 (P < 0.01). Also, propulsion showed statistically significant improvements after exercise with EX1 (P < 0.01) Regarding changes of the gait posture, there was a statistically significant improvement in pelvic movement (P < 0.05). In the functional evaluation, the time required was statistically significantly reduced in the timed up and go test (P < 0.05). CONCLUSION: These results demonstrate that a 4-week exercise program with EX1 was effective in improving the functional gait of the elderly. However, because the participants were 21, it is difficult to generalize the results. TRIAL REGISTRATION: Clinical Research Information Service, KCT0007367. Registered 08/06/2022.

Weak thermal state quadrature-noise shadow imaging.

In this work, we theoretically and experimentally demonstrate the possibility to create an image of an opaque object using a few-photon thermal optical field. We utilize the quadrature-noise shadow imaging (QSI) technique that detects the changes in the quadrature-noise statistics of the probe beam after its interaction with an object. We show that such a thermal QSI scheme has an advantage over the classical differential imaging when the effect of dark counts is considered. At the same time, the easy availability of thermal sources for any wavelength makes the method practical for broad range of applications, not accessible with, e.g., quantum squeezed light. As a proof of principle, we implement this scheme by two different light sources: a pseudo-thermal beam generated by rotating ground glass (RGG) method and a thermal beam generated by four-wave mixing (FWM) method. The RGG method shows simplicity and robustness of QSI scheme while the FWM method validates theoretical signal-to-noise ratio predictions. Finally, we demonstrate low-light imaging abilities with QSI by imaging a biological specimen on a CCD camera, detecting as low as 0.03 photons on average per pixel per 1.7 µs exposure.

Wave-front reconstruction via single-pixel homodyne imaging.

We combine single-pixel imaging and homodyne detection to perform full object recovery (phase and amplitude). Our method does not require any prior information about the object or the illuminating fields. As a demonstration, we reconstruct the optical properties of several semi-transparent objects and find that the reconstructed complex transmission has a phase precision of 0.02 radians and a relative amplitude precision of 0.01.

Bile-acid levels and lung maturity test in patients with intrahepatic cholestasis of pregnancy.

OBJECTIVES: Prolonged fetal exposure to maternal bile acids have been linked to fetal lung injury, but it is not known if it affects production of surfactant or fetal lung maturity tests. We set out to determine if elevated total bile acid (TBA) levels predict delayed fetal lung maturity (FLM) in patients with intrahepatic cholestasis of pregnancy (ICP). METHODS: A retrospective cohort study examining patients with ICP who underwent amniocentesis between 36+0 and 37+6 between 2005 and 2014. Primary goal was to identify if a relationship exists between TBA levels and FLM defined as Lecithin:Sphingomyelin >2.5, detectable Phosphatidylglycerol, or lamellar body count of >50,000. RESULTS: Among the 113 patients, there was no statistically significant difference in TBA levels between women with FLM and those with immaturity (31.3 [21.6, 44.5] µmol/L and 34.9 [23.9, 62.3] µmol/L respectively; p=0.16). Logistic regression performed using predefined TBA levels of 20, 30, 40 and 50 µmol/L revealed that TBA levels did not predict a negative FLM test at time of amniocentesis. CONCLUSIONS: TBA levels do no predict presence or absence of FLM between 36+0 and 37+6 weeks of gestation. Though certain pregnancy complications can affect FLM, we could not identify a correlation between TBA levels and an accelerated or delayed lung maturation process.

Critical Inhaler Administration Errors of Patients on Pressurized Meter Dose Inhaler (pMDI): A Hospital-Based Cross-Sectional Study in Malaysia.

Background: Inhaler technique errors can affect the disease outcome through reduced deposition of medication in the lungs with certain errors were more likely to deter the optimum drug from reaching the lung. The objective of this study was to evaluate the pressurized metered-dose inhaler (pMDI) critical technique errors among asthma and COPD patients, and to investigate the predictors of those errors. Methods: A cross-sectional, observational, and multi-centered study conducted in 3 major hospitals in the state of Penang, Malaysia. Asthma and COPD patients aged 18 years or older consented to the study were consecutively recruited if they were at least on 1 pMDI without mouthpiece spacer or facemask space. Direct observation of the patient's technique was recorded using a standard checklist and certain steps in the checklist were pre-determined as critical steps. The number of patients missed or incorrectly performed the steps including the critical steps were documented. Using logistic regression, the factors associated with the critical errors were determined, and the correlation was evaluated between age and pMDI knowledge score with critical inhalation steps score. Results: Of 209 patients observed, only less than half (40.7%) could perform all the critical pMDI steps correctly. Low education level was the only factor associated with critical inhaler errors. The increased knowledge of their inhaled medication was found to positively correlate with the correct critical inhalation steps. The critical errors also increase with the increased age of patients. Conclusion: The majority of the study population make inhalation error particularly in critical steps. Training and education intervention programs may help patients with lower education level, as well as those of advanced age and lack of knowledge of their inhaled medication because those populations are at a greater risk of committing critical errors in their use of pMDI.

Correlation between cardiopulmonary metabolic energy cost and lower-limb muscle activity during inclined treadmill gait in older adults.

BACKGROUND: Inclined walking requires more cardiopulmonary metabolic energy and muscle strength than flat-level walking. This study sought to investigate changes in lower-limb muscle activity and cardiopulmonary metabolic energy cost during treadmill walking with different inclination grades and to discern any correlation between these two measures in older adults. METHODS: Twenty-four healthy older adults (n = 11 males; mean age: 75.3 ± 4.0 years) participated. All participants walked on a treadmill that was randomly inclined at 0% (condition 1), 10% (condition 2), and 16% (condition 3) for five minutes each. Simultaneous measurements of lower-limb muscle activity and cardiopulmonary metabolic energy cost during inclined treadmill walking were collected. Measured muscles included the rectus abdominis (RA), erector spinae (ES), rectus femoris (RF), biceps femoris (BF), vastus medialis (VM), tibialis anterior (TA), medial head of the gastrocnemius (GCM), and soleus (SOL) muscles on the right side. RESULTS: As compared with 0% inclined treadmill gait, the 10% inclined treadmill gait increased the net cardiopulmonary metabolic energy cost by 22.9%, while the 16% inclined treadmill gait increased the net cardiopulmonary metabolic energy cost by 44.2%. In the stance phase, as the slope increased, activity was significantly increased in the RA, RF, VM, BF, GCM, and SOL muscles. In the swing phase, As the slope increased activity was significantly increased in the RA, RF, VM, BF, and TA muscles. SOL muscle activity was most relevant to the change in cardiopulmonary metabolic energy cost in the stance phase of inclined treadmill walking. The relationship between the increase in cardiopulmonary metabolic energy cost and changes in muscle activity was also significant in the VM, GCM, and RF. CONCLUSION: This study demonstrated that changes in SOL, VM, GCM, and RA muscle activity had a significant relationship with cardiopulmonary metabolic energy cost increment during inclined treadmill walking. These results can be used as basic data for various gait-training programs and as an indicator in the development of assistive algorithms of wearable walking robots for older adults. TRIAL REGISTRATION: Clinical trials registration information: ClinicalTrials.gov Identifier: NCT04614857 (05/11/2020).

Proof-of-Concept of a Sensor-Based Evaluation Method for Better Sensitivity of Upper-Extremity Motor Function Assessment.

In rehabilitation, the Fugl-Meyer assessment (FMA) is a typical clinical instrument to assess upper-extremity motor function of stroke patients, but it cannot measure fine changes of motor function (both in recovery and deterioration) due to its limited sensitivity. This paper introduces a sensor-based automated FMA system that addresses this limitation with a continuous rating algorithm. The system consists of a depth sensor (Kinect V2) and an algorithm to rate the continuous FM scale based on fuzzy inference. Using a binary logic based classification method developed from a linguistic scoring guideline of FMA, we designed fuzzy input/output variables, fuzzy rules, membership functions, and a defuzzification method for several representative FMA tests. A pilot trial with nine stroke patients was performed to test the feasibility of the proposed approach. The continuous FM scale from the proposed algorithm exhibited a high correlation with the clinician rated scores and the results showed the possibility of more sensitive upper-extremity motor function assessment.

Analysis of angular dispersion induced by wavefront rotation in nanosecond optical parametric chirped pulse amplification.

Angular dispersion observed in a nanosecond optical parametric chirped-pulse amplification (ns-OPCPA) amplifier adopted in the frontend of a multi-PW laser was analyzed. The theory on the angular dispersion, extended by including the wavefront rotation and the pulse front tilt of a strongly chirped laser pulse, revealed that the wavefront rotation is a major contributor to the angular dispersion, as compared to the pulse front tilt, in a ns-OPCPA amplifier. It was also shown that the wavefront rotation could be introduced by the phase mismatch and the noncollinear propagation angle in the noncollinear ns-OPCPA amplifier. The theoretical prediction was experimentally verified by measuring the angular dispersion of the ns-OPCPA frontend installed in the 20-fs, 4-PW Ti:Sapphire laser. We emphasize the importance of the proper characterization and control of the angular dispersion in the ns-OPCPA amplifier since the focus intensity of an ultrahigh power laser could be significantly reduced due to the spatiotemporal effect even for small induced angular dispersion.

Highly efficient double plasma mirror producing ultrahigh-contrast multi-petawatt laser pulses.

We present a highly efficient double plasma mirror (DPM) that provides ultrahigh-contrast multi-petawatt (PW) laser pulses with a temporal contrast ratio reaching 1017 up to 160 ps and 1012 up to 2 ps before the main pulse. The high reflectivity of 70%, along with the high-contrast enhancement factor of 700,000, was achieved from the DPM installed after the final stage of a 4 PW Ti:sapphire laser. The 4 PW laser was equipped with cross-polarized wave generation and optical parametric chirped-pulse amplification stages for initial high-contrast operation. The DPM operation was undertaken with conditions that did not modify the spatiotemporal profiles of incident multi-PW laser pulses. This highly efficient DPM with the high-contrast enhancement promises the utilization of multiple PMs as a practical rear end for upcoming tens of petawatt lasers to achieve ultrahigh temporal contrast.

Quantum-Limited Squeezed Light Detection with a Camera.

We present a technique for squeezed light detection based on direct imaging of the displaced-squeezed-vacuum state using a CCD camera. We show that the squeezing parameter can be accurately estimated using only the first two moments of the recorded pixel-to-pixel photon fluctuation statistics, with accuracy that rivals that of the standard squeezing detection methods such as a balanced homodyne detection. Finally, we numerically simulate the camera operation, reproducing the noisy experimental results with low signal samplings and confirming the theory with high signal samplings.

Wearable hip-assist robot modulates cortical activation during gait in stroke patients: a functional near-infrared spectroscopy study.

BACKGROUND: Gait dysfunction is common in post-stroke patients as a result of impairment in cerebral gait mechanism. Powered robotic exoskeletons are promising tools to maximize neural recovery by delivering repetitive walking practice. OBJECTIVES: The purpose of this study was to investigate the modulating effect of the Gait Enhancing and Motivating System-Hip (GEMS-H) on cortical activation during gait in patients with chronic stroke. METHODS: Twenty chronic stroke patients performed treadmill walking at a self-selected speed either with assistance of GEMS-H (GEMS-H) or without assistance of GEMS-H (NoGEMS-H). Changes in oxygenated hemoglobin (oxyHb) concentration in the bilateral primary sensorimotor cortex (SMC), premotor cortices (PMC), supplemental motor areas (SMA), and prefrontal cortices (PFC) were recorded using functional near infrared spectroscopy. RESULTS: Walking with the GEMS-H promoted symmetrical SMC activation, with more activation in the affected hemisphere than in NoGEMS-H conditions. GEMS-H also decreased oxyHb concentration in the late phase over the ipsilesional SMC and bilateral SMA (P < 0.05). CONCLUSIONS: The results of the present study reveal that the GEMS-H promoted more SMC activation and a balanced activation pattern that helped to restore gait function. Less activation in the late phase over SMC and SMA during gait with GEMS-H indicates that GEMS-H reduces the cortical participation of stroke gait by producing rhythmic hip flexion and extension movement and allows a more coordinate and efficient gait patterns. Trial registration NCT03048968. Registered 06 Feb 2017.

Training for Walking Efficiency With a Wearable Hip-Assist Robot in Patients With Stroke: A Pilot Randomized Controlled Trial.

Background and Purpose- The purpose of this study was to investigate the effects of gait training with a newly developed wearable hip-assist robot on locomotor function and efficiency in patients with chronic stroke. Methods- Twenty-eight patients with stroke with hemiparesis were initially enrolled, and 26 patients completed the randomized controlled trial (14 in the experimental and 12 in the control groups). The experimental group participated in a gait training program over a total of 10 sessions, including 5 treadmill sessions and 5 over-ground gait training sessions while wearing a hip-assist robot, the Gait Enhancing and Motivating System (GEMS, Samsung Advanced Institute of Technology, Suwon, Republic of Korea). The control group received gait training without Gait Enhancing and Motivating System. Primary outcome measured locomotor function and cardiopulmonary metabolic energy efficiency. Also, secondary outcome measured motor function and balance parameter. Results- Compared with the control group, the experimental group had significantly greater improvement in spatiotemporal gait parameters and muscle efforts after the training intervention (P<0.05). The net cardiopulmonary metabolic energy cost (mL·kg-1·min-1) was also reduced by 14.71% in the experimental group after the intervention (P<0.01). Significant group×time interactions were observed for all parameters (P<0.05). Cardiopulmonary metabolic efficiency was strongly correlated with gait symmetry ratio in the experimental group (P<0.01). Conclusions- Gait training with Gait Enhancing and Motivating System was effective for improving locomotor function and cardiopulmonary metabolic energy efficiency during walking in patients with stroke. These findings suggest that robotic locomotor training can be adopted for rehabilitation of patients with stroke with gait disorders. Clinical Trial Registration- URL: https://clinicaltrials.gov. Unique identifier: NCT02843828.

Achieving the laser intensity of 5.5×1022 W/cm2 with a wavefront-corrected multi-PW laser.

The generation of ultrahigh intensity laser pulses was investigated by tightly focusing a wavefront-corrected multi-petawatt Ti:sapphire laser. For the wavefront correction of the PW laser, two stages of deformable mirrors were employed. The multi-PW laser beam was tightly focused by an f/1.6 off-axis parabolic mirror and the focal spot profile was measured. After the wavefront correction, the Strehl ratio was about 0.4, and the spot size in full width at half maximum was 1.5×1.8 µm2, close to the diffraction-limited value. The measured peak intensity was 5.5×1022 W/cm2, achieving the highest laser intensity ever reached.

Laser Acceleration of Highly Energetic Carbon Ions Using a Double-Layer Target Composed of Slightly Underdense Plasma and Ultrathin Foil.

We report the experimental generation of highly energetic carbon ions up to 48 MeV per nucleon by shooting double-layer targets composed of well-controlled slightly underdense plasma and ultrathin foils with ultraintense femtosecond laser pulses. Particle-in-cell simulations reveal that carbon ions are ejected from the ultrathin foils due to radiation pressure and then accelerated in an enhanced sheath field established by the superponderomotive electron flow. Such a cascaded acceleration is especially suited for heavy ion acceleration with femtosecond laser pulses. The breakthrough of heavy ion energy up to many tens of MeV/u at a high repetition rate would be able to trigger significant advances in nuclear physics, high energy density physics, and medical physics.

Modulation of Cortical Activity by High-Frequency Whole-Body Vibration Exercise: An fNIRS Study.

CONTEXT: Whole-body vibration (WBV) has shown many positive effects on the human body in rehabilitation and clinical settings in which vibration has been used to elicit muscle contractions in spastic and paretic muscles. OBJECTIVE: The purpose of this study was to investigate whether WBV exercise (WBVe) differently modulates the cortical activity associated with motor and prefrontal function based on its frequency. METHODS: A total of 18 healthy male adults (mean age: 25.3 [2.4] y) participated in this study and performed WBVe (Galileo Advanced plus; Novotec Medical, Pforzheim, Germany) under 3 different vibration frequency conditions (4-mm amplitude with 10-, 20-, and 27-Hz frequencies) and a control condition (0-mm amplitude with 0-Hz frequency). Each condition consisted of 2 alternating tasks (squatting and standing) every 30 seconds for 5 repetitions. All subjects performed the 4 conditions in a randomized order. MAIN OUTCOME MEASURE: Cortical activation during WBVe was measured by relative changes in oxygenated hemoglobin concentration over the primary motor cortex, premotor cortex, supplementary motor area, and prefrontal and somatosensory cortices using functional near-infrared spectroscopy. RESULTS: Oxygenated hemoglobin concentration was higher during the 27-Hz vibration condition than the control and 10-Hz vibration conditions. Specifically, these changes were pronounced in the bilateral primary motor cortex (P < .05) and right prefrontal cortex (P < .05). In contrast, no significant changes in oxygenated hemoglobin concentration were observed in any of the cortical areas during the 10-Hz vibration condition compared with the control condition. CONCLUSION: This study provides evidence that the motor network and prefrontal cortical areas of healthy adult males can be activated by 27-Hz WBVe. However, WBVe at lower frequencies did not induce significant changes in cortical activation.

Contrasting life histories contribute to divergent patterns of genetic diversity and population connectivity in freshwater sculpin fishes.

BACKGROUND: Life history characteristics are considered important factors influencing the evolutionary processes of natural populations, including the patterns of population genetic structure of a species. The sister species Cottus hangiongensis and C. koreanus are small bottom-dwelling freshwater sculpin fishes from South Korea that display marked life history divergence but are morphologically nearly indistinguishable. Cottus hangiongensis evolved an 'amphidromous' life history with a post-hatching pelagic larval phase. They spawn many small eggs in the low reaches of rivers, and hatched larvae migrate to the sea before returning to grow to maturity in the river mouth. In contrast, C. koreanus evolved a 'fluvial' landlocked type with benthic larvae. They release a smaller number of larger eggs, and the larvae undergo direct development, remaining benthic in the upstream rivers throughout their entire lives. We tested whether there were differences in patterns and levels of within-population genetic diversities and spatial population structure between the two closely related Korean sculpins using mitochondrial DNA control region sequences and seven nuclear microsatellite loci. RESULTS: The combined analyses of both marker sets revealed that C. hangiongensis harboured considerably higher levels of within-population genetic diversities (e.g. haplotype/allelic richness, heterozygosities) than C. koreanus. In contrast, the fluvial sculpin exhibited noticeably more spatial population structure than did the amphidromous sculpin, as suggested by pairwise FST statistics. The finding that C. hangiongensis individuals comprised a single random mating population across the east-flowing river basins in the Korean Peninsula, whereas C. koreanus individuals comprised genetically discrete individual populations, was further supported by an individual-based Bayesian population assignment and also factorial correspondence analyses. CONCLUSIONS: The higher genetic diversity, but lower population structure, of the amphidromous sculpin relative to the fluvial sculpin may have resulted from its greater larval dispersal and also possibly, higher fecundity accompanied by an amphidromous life history. Hence, we conclude that contrasting early life histories - including the presence or absence of the pelagic larval phase - may have led to divergent patterns of within-population genetic diversities and spatial population structure between the sister Cottus species following speciation from a common ancestor of marine sculpin.

Sub-shot-noise-limited phase estimation via SU(1,1) interferometer with thermal states.

We theoretically study the phase sensitivity of an SU(1,1) interferometer with a thermal state and a squeezed vacuum state as inputs and parity detection as the measurement. We find that the phase sensitivity can beat the shot-noise limit and approaches the Heisenberg limit, with increasing input photon number, in an ideal situation. We also consider the effect of various noises, including photon loss, dark counts, and thermal photon noise. Our results show that the phase sensitivity is below the shot-noise limit with photon loss and dark counts, but cannot beat the shot-noise limit in the presence of thermal noise.

Spectral shaping of an OPCPA preamplifier for a sub-20-fs multi-PW laser.

We developed an OPCPA preamplifier with an actively shaped output spectrum to obtain a sub-20-fs-duration pulse for a 4-PW laser. The active spectral shaping was facilitated by controlling the temporal profile of a pump pulse in the OPCPA preamplifier. By optimizing the output spectrum of the OPCPA to compensate for the gain-depletion effect in the 4-PW laser, a final laser pulse with a broad spectrum of 101-nm in width (FWHM), resulting in a short pulse duration of 17 fs, was achieved.