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Femtosecond laser

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https://www.readbyqxmd.com/read/28430519/energy-resolved-ultrashort-delays-of-photoelectron-emission-clocked-by-orthogonal-two-color-laser-fields
#1
Xiaochun Gong, Cheng Lin, Feng He, Qiying Song, Kang Lin, Qinying Ji, Wenbin Zhang, Junyang Ma, Peifen Lu, Yunquan Liu, Heping Zeng, Weifeng Yang, Jian Wu
A phase-controlled orthogonal two-color (OTC) femtosecond laser pulse is employed to probe the time delay of photoelectron emission in the strong-field ionization of atoms. The OTC field spatiotemporally steers the emission dynamics of the photoelectrons and meanwhile allows us to unambiguously distinguish the main and sideband peaks of the above-threshold ionization spectrum. The relative phase shift between the main and sideband peaks, retrieved from the phase-of-phase of the photoelectron spectrum as a function of the laser phase, gradually decreases with increasing electron energy, and becomes zero for the fast electron which is mainly produced by the rescattering process...
April 7, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28430252/measuring-spatiotemporal-ultrafast-field-structures-of-pulses-from-multimode-optical-fibers
#2
Zhe Guang, Michelle Rhodes, Rick Trebino
Ultrashort pulses emerging from multimode optical fibers are spatiotemporally complex, because inside these fibers the modes have different spatial intensity patterns and experience different propagation velocities and dispersions. To determine the spatiotemporal field from multimode fibers, we applied a technique for the complete measurement of the output pulses called a spatially and temporally resolved intensity and phase evaluation device: full information from a single hologram. It yields the complete electric field over space and time from multiple digital holograms, simultaneously recorded at different frequencies on a single camera frame...
April 20, 2017: Applied Optics
https://www.readbyqxmd.com/read/28424320/trpa1-expression-and-its-functional-activation-in-rodent-cortex
#3
Ehsan Kheradpezhouh, Julian M C Choy, Vincent R Daria, Ehsan Arabzadeh
TRPA1 is a non-selective cation channel involved in pain sensation and neurogenic inflammation. Although TRPA1 is well established in a number of organs including the nervous system, its presence and function in the mammalian cortex remains unclear. Here, we demonstrate the expression of TRPA1 in rodent somatosensory cortex through immunostaining and investigate its functional activation by whole-cell electrophysiology, Ca(2+) imaging and two-photon photoswitching. Application of TRPA1 agonist (AITC) and antagonist (HC-030031) produced significant modulation of activity in layer 5 (L5) pyramidal neurons in both rats and mice; AITC increased intracellular Ca(2+) concentrations and depolarized neurons, and both effects were blocked by HC-030031...
April 2017: Open Biology
https://www.readbyqxmd.com/read/28421140/comparison-of-corneal-power-and-astigmatism-between-simulated-keratometry-true-net-power-and-total-corneal-refractive-power-before-and-after-smile-surgery
#4
Yishan Qian, Yan Liu, Xingtao Zhou, Rajeev Krishnan Naidu
Purpose. To compare the mean corneal power (Km) and total astigmatism (Ka) estimated by three methods: simulated keratometry (simK), true net power (TNP), and total corneal refractive power (TCRP) before and after femtosecond laser small incision lenticule extraction (SMILE) surgery. Methods. A retrospective, cross-sectional study. SimK, TNP, and TCRP from a Scheimpflug analyzer were obtained from 144 patients before and 6 months after SMILE surgery. Km and Ka were recorded as the mean of individual paracentral rings of 1...
2017: Journal of Ophthalmology
https://www.readbyqxmd.com/read/28420926/femto-lasik-the-recent-innovation-in-laser-assisted-refractive-surgery
#5
Zubair Shahid Bashir, Muhammad Hassaan Ali, Ayesha Anwar, Muhammad Hammad Ayub, Nadeem Hafeez Butt
Femtosecond laser has been introduced in refractive surgery to create a thin-hinged corneal flap without using any blade. The current review was planned to analyse and compare femtosecond-assisted laser in-situ keratomileusis (LASIK), the latest refractive procedure, with conventional techniques in refractive surgery. The analysis showed that femtosecond-assisted LASIK yielded more predictable corneal flaps, lesser ocular aberrations, better uncorrected visual acuity, lesser variations in intraocular pressure (IOP) and fewer chances of developing dry eyes...
April 2017: JPMA. the Journal of the Pakistan Medical Association
https://www.readbyqxmd.com/read/28415544/%C3%AE-pyrophosphate-a-potential-biomaterial-for-dental-applications
#6
A D Anastasiou, S Strafford, O Posada-Estefan, C L Thomson, S A Hussain, T J Edwards, M Malinowski, N Hondow, N K Metzger, C T A Brown, M N Routledge, A P Brown, M S Duggal, A Jha
Tooth hypersensitivity is a growing problem affecting both the young and ageing population worldwide. Since an effective and permanent solution is not yet available, we propose a new methodology for the restoration of dental enamel using femtosecond lasers and novel calcium phosphate biomaterials. During this procedure the irradiated mineral transforms into a densified layer of acid resistant iron doped β-pyrophosphate, bonded with the surface of eroded enamel. Our aim therefore is to evaluate this densified mineral as a potential replacement material for dental hard tissue...
June 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
https://www.readbyqxmd.com/read/28414375/evaluation-of-femtosecond-laser-damage-to-gold-pulse-compression-gratings-fabricated-by-magnetron-sputtering-and-e-beam-evaporation
#7
Leilei Wang, Fanyu Kong, Zhilin Xia, Yunxia Jin, Haopeng Huang, Linxin Li, Junming Chen, Yun Cui, Jianda Shao
In this study, two kinds of Au-coated gratings (ACGs) with a period of 1740 lines/mm were fabricated and evaluated. For these ACG samples, magnetron sputtering and e-beam evaporation were used as the gold deposition process, and the samples had a bandwidth of at least 170 nm, with the -1st-order diffraction efficiency exceeding 90% around the center wavelength of 800 nm. The one-on-one damage threshold of ACGs fabricated by magnetron sputtering and e-beam evaporation measured at a pulse width of 60 fs was 0...
April 10, 2017: Applied Optics
https://www.readbyqxmd.com/read/28414346/mixture-fraction-measurements-with-femtosecond-laser-electronic-excitation-tagging
#8
Benjamin R Halls, Naibo Jiang, James R Gord, Paul M Danehy, Sukesh Roy
Tracer-free mixture-fraction measurements were demonstrated in a jet using femtosecond-laser electronic-excitation tagging. Measurements were conducted across a turbulent jet at several downstream locations both in a pure-nitrogen jet exiting into an air-nitrogen mixture and in a jet containing an air-nitrogen mixture exiting into pure nitrogen. The signal was calibrated with known concentrations of oxygen in nitrogen. The spatial resolution of the measurement was ∼180  μm. The measurement uncertainty ranged from 5% to 15%, depending on the mixture fraction and location within the beam, under constant temperature and pressure conditions...
April 10, 2017: Applied Optics
https://www.readbyqxmd.com/read/28412801/-preliminary-report-on-the-application-of-femtosecond-laser-assisted-anterior-capsulotomy-in-intumescent-white-cataract-surgery
#9
T T Peng, Y Wang, X Y Bao
Objective: To assess the effect of femtosecond laser-assisted anterior capsulotomy in intumescent white cataract surgery. Methods: Retrospective case series study. One hundred and fifty cataract patients (150 eyes) from June 2014 to June 2015 in Wuhan Aier ophthalmology hospital were enrolled in this study. They were divided into three groups: 50 intumescent white cataract patients (50 eyes) in the study group were performed femtosecond laser-assisted capsulotomy (LenSx system) operation selectively. Fifty intumescent white cataract patients (50 eyes) underwent normal manual continuous circular capsulorhexis as the control group 1...
April 11, 2017: [Zhonghua Yan Ke za Zhi] Chinese Journal of Ophthalmology
https://www.readbyqxmd.com/read/28412070/evaluation-of-femtosecond-laser-intrastromal-incision-location-using-optical-coherence-tomography
#10
Li Wang, Lai Jiang, Katie Hallahan, Zaina N Al-Mohtaseb, Douglas D Koch
PURPOSE: To use optical coherence tomography (OCT) to evaluate the femtosecond laser intrastromal incisions made during cataract surgery to reduce corneal astigmatism. DESIGN: Retrospective case series. PARTICIPANTS: Seventy-seven eyes of 77 patients. METHODS: Paired intrastromal incisions were created using the Catalys femtosecond laser (Abbott Medical Optics, Inc., Santa Ana, CA). The planned intrastromal incision parameters were 20% uncut anterior, 20% uncut posterior, midpoint depth of 50%, and 90° side cut angle...
April 12, 2017: Ophthalmology
https://www.readbyqxmd.com/read/28410727/transection-and-explantation-of-intraocular-lenses-using-femtosecond-lasers
#11
Chandra Bala, Ushasree Pattamatta, Thomas Chan, Jeffrey Shi, Kerrie Meades
We present 2 cases in which a femtosecond laser was used in vitro to transect hydrophilic acrylic intraocular lenses (IOLs). At 8 μJ with 3 μm spot separation and 6 μm line separation, no charring occurred and there was no increase in total organic carbon. In vivo, the IOLs were successfully transected in the capsular bag (Case 1, opaque IOL) and the sulcus (Case 2, subluxated IOL post-pneumatic displacement of submacular hemorrhage) and explanted through a clear corneal incision (∼3.0 mm). At 3 months, in Case 1, the corrected distance visual acuity (CDVA) improved from 6/24 to 6/5, astigmatism improved by 0...
March 2017: Journal of Cataract and Refractive Surgery
https://www.readbyqxmd.com/read/28410717/greater-vertical-spot-spacing-to-improve-femtosecond-laser-capsulotomy-quality
#12
Tim Schultz, Stephanie C Joachim, Rozina Noristani, Wendell Scott, H Burkhard Dick
PURPOSE: To evaluate the effect of adapted capsulotomy laser settings on the cutting quality in femtosecond laser-assisted cataract surgery. SETTING: Ruhr-University Eye Clinic, Bochum, Germany. DESIGN: Prospective randomized case series. METHODS: Eyes were treated with 1 of 2 laser settings. In Group 1, the regular standard settings were used (incisional depth 600 μm, pulse energy 4 μJ, horizontal spot spacing 5 μm, vertical spot spacing 10 μm, treatment time 1...
March 2017: Journal of Cataract and Refractive Surgery
https://www.readbyqxmd.com/read/28409816/regenerated-volume-gratings-in-pmma-after-femtosecond-laser-writing
#13
Yu Matushiro, Saulius Juodkazis, Koji Hatanaka, Wataru Watanabe
Self-regeneration of volume gratings recorded inside polymethyl methacrylate (PMMA) after 70-100 days is demonstrated. First, volume gratings were made inside PMMA by femtosecond laser writing. The diffraction efficiency of the gratings reached the maximum-was regenerated-following an initial slow decrease within the first several days after the fabrication. Time-lapse measurements of the diffraction efficiency in both top-plane (as laser written) and side-plane illumination were used to monitor changes of the diffraction efficiency...
April 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28409801/single-mode-unidirectional-microcavity-laser
#14
Zhen-Nan Tian, Feng Yu, Yan-Hao Yu, Jun-Jie Xu, Qi-Dai Chen, Hong-Bo Sun
In this Letter, we report a suspended whispering gallery mode microdisk with a hole pierced through its surface. The novel disk is made up of Rhodamine B-doped resin, which is fabricated by femtosecond laser direct writing technology. The pierced microcavity achieves highly directional emission of single-mode lasing with a far field divergence angle of about 10 deg, and its high Q factor exceeds 2.6×10<sup>3</sup>. The excellent properties are confirmed by numerical simulation based on the finite-difference time-domain method...
April 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28409800/high-efficiency-femtosecond-raman-soliton-generation-with-a-tunable-wavelength-beyond-2%C3%A2-%C3%A2-%C3%AE-m
#15
Jiaqi Luo, Biao Sun, Junhua Ji, Eng Leong Tan, Ying Zhang, Xia Yu
We report an efficient Raman soliton laser system by optimizing the chirp of input pulses. The highest efficiency of energy transferred to a Raman soliton is up to 97%, and the tunable range is from 1.98 to 2.31 μm. The pulse width of these tunable Raman solitons remains below 200 fs. The efficiency and the wavelength range are mainly limited by the background loss of the silica fiber.
April 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28409788/femtosecond-semiconductor-laser-system-with-resonator-internal-dispersion-adaptation
#16
Rouven H Pilny, Benjamin Döpke, Jan C Balzer, Carsten Brenner, Andreas Klehr, Andrea Knigge, Günther Tränkle, Martin R Hofmann
We present a femtosecond laser diode system that is capable of autonomously adjusting itself to compensate for the external dispersion in an arbitrary application. The laser system contains a spatial light modulator inside the cavity which is controlled by an evolutionary algorithm in order to allow for phase and amplitude shaping of the laser emission. The cavity-internal dispersion control is shown to be much more efficient than an external control with a pulse shaper.
April 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28407165/comparison-of-corneal-epithelial-remodeling-after-femtosecond-laser-assisted-lasik-and-small-incision-lenticule-extraction-smile
#17
Ik-Hee Ryu, Bong Jun Kim, Jong-Hyuck Lee, Sun Woong Kim
PURPOSE: To comparatively investigate changes in epithelial thickness between myopic femtosecond laser-assisted LASIK (FS-LASIK) and small incision lenticule extraction (SMILE). METHODS: This study compared the topographic epithelial thickness changes in 175 myopic eyes undergoing FS-LASIK (62 eyes) or SMILE (113 eyes). Epithelial thickness was obtained using spectral-domain optical coherence tomography before surgery and 1 and 3 months after surgery. Topographic epithelial thickness obtained by automatic algorithm and thickness variability (standard deviation over 17 imaged areas) was compared between two groups...
April 1, 2017: Journal of Refractive Surgery
https://www.readbyqxmd.com/read/28407162/effects-of-short-term-preoperative-topical-ketorolac-on-pupil-diameter-in-eyes-undergoing-femtosecond-laser-assisted-capsulotomy
#18
Vasilios F Diakonis, Georgios A Kontadakis, Apostolos G Anagnostopoulos, Nilufer Yesilirmak, Daniel P Waren, Florence Cabot, Sonia H Yoo, Kendall E Donaldson
PURPOSE: To assess pupil diameter before and after femtosecond laser-assisted capsulotomy in patients who were pretreated with a short-term topical nonsteroidal anti-inflammatory drug (NSAID) (ketorolac) versus those without pretreatment. METHODS: This prospective, randomized, observational case series included consecutive patients scheduled to undergo cataract extraction using the Catalys femtosecond laser platform (Abbott Medical Optics, Inc., Santa Ana, CA) to perform only capsulotomies...
April 1, 2017: Journal of Refractive Surgery
https://www.readbyqxmd.com/read/28407161/preliminary-evidence-of-successful-near-vision-enhancement-with-a-new-technique-presbyopic-allogenic-refractive-lenticule-pearl-corneal-inlay-using-a-smile-lenticule
#19
Soosan Jacob, Dhivya Ashok Kumar, Amar Agarwal, Athiya Agarwal, Ramalingam Aravind, A I Saijimol
PURPOSE: To describe a new technique (PrEsbyopic Allogenic Refractive Lenticule [PEARL] inlay) using an allogenic corneal inlay prepared from a small incision lenticule extraction (SMILE) lenticule. METHODS: A SMILE lenticule of specified thickness (mean: 61.5 ± 3.32 µm) was trephined at the center to 1-mm diameter and implanted in the cornea on the coaxially sighted light reflex under a femtosecond laser-created cap of 120 µm in the nondominant eye of presbyopic patients...
April 1, 2017: Journal of Refractive Surgery
https://www.readbyqxmd.com/read/28406144/nanoscale-interface-confinement-of-ultrafast-spin-transfer-torque-driving-non-uniform-spin-dynamics
#20
Ilya Razdolski, Alexandr Alekhin, Nikita Ilin, Jan P Meyburg, Vladimir Roddatis, Detlef Diesing, Uwe Bovensiepen, Alexey Melnikov
Spintronics had a widespread impact over the past decades due to transferring information by spin rather than electric currents. Its further development requires miniaturization and reduction of characteristic timescales of spin dynamics combining the sub-nanometre spatial and femtosecond temporal ranges. These demands shift the focus of interest towards the fundamental open question of the interaction of femtosecond spin current (SC) pulses with a ferromagnet (FM). The spatio-temporal properties of the impulsive spin transfer torque exerted by ultrashort SC pulses on the FM open the time domain for probing non-uniform magnetization dynamics...
April 13, 2017: Nature Communications
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