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Femtosecond laser

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https://www.readbyqxmd.com/read/29345707/synthesis-and-characterization-of-a-photocleavable-collagen-like-peptide
#1
Alfredo Ornelas, Kaitlyn N Williams, Kevin A Hatch, Aurelio Paez, Angela C Aguilar, Cameron C Ellis, Nishat Tasnim, Supriyo Ray, Carl W Dirk, Thomas Boland, Binata Joddar, Chunqiang Li, Katja Michael
A 34-amino acid long collagen-like peptide rich in proline, hydroxyproline, and glycine, and with four photoreactive N-acyl-7-nitroindoline units incorporated into the peptide backbone was synthesized by on-resin fragment condensation. Its circular dichroism supports a stable triple helix structure. The built-in photochemical function enables the decomposition of the peptide into small peptide fragments by illumination with UV light of 350 nm in aqueous solution. Illumination of a thin film of the peptide, or a thin film of a photoreactive amino acid model compound containing a 5-bromo-7-nitroindoline moiety, with femtosecond laser light at 710 nm allows for the creation of well-resolved micropatterns...
January 18, 2018: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/29341630/terahertz-sum-frequency-excitation-of-a-raman-active-phonon
#2
Sebastian Maehrlein, Alexander Paarmann, Martin Wolf, Tobias Kampfrath
In stimulated Raman scattering, two incident optical waves induce a force oscillating at the difference of the two light frequencies. This process has enabled important applications such as the excitation and coherent control of phonons and magnons by femtosecond laser pulses. Here, we experimentally and theoretically demonstrate the so far neglected up-conversion counterpart of this process: THz sum-frequency excitation of a Raman-active phonon mode, which is tantamount to two-photon absorption by an optical transition between two adjacent vibrational levels...
September 22, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/29340400/femtosecond-laser-induced-underwater-superaerophilic-and-superaerophobic-pdms-sheets-with-through-microholes-for-selective-passage-of-air-bubbles-and-further-collection-of-underwater-gas
#3
Jiale Yong, Feng Chen, Jinglan Huo, Yao Fang, Qing Yang, Jingzhou Zhang, Xun Hou
Controlling underwater bubble behavior on a solid surface is of great research significance, particularly in extreme cases. However, the realization of artificial underwater superaerophobic or superaerophilic surfaces is still a challenge. Herein, a micro/nanoscale hierarchical rough structure was formed on polydimethylsiloxane (PDMS) surface by one-step femtosecond laser ablation. The as-prepared surface showed superhydrophobicity in air and superaerophilicity in water. Interestingly, the wettability of such a PDMS surface could be easily switched to in-air superhydrophilicity and underwater superaerophobicity once it was further irradiated by oxygen plasma because the surface chemistry changed...
January 17, 2018: Nanoscale
https://www.readbyqxmd.com/read/29338182/-infinite-sensitivity-of-black-silicon-ammonia-sensor-achieved-by-optical-and-electric-dual-drives
#4
Xiao-Long Liu, Suwan Zhu, Hai-Bin Sun, Yue Hu, Sheng-Xiang Ma, Xi-Jing Ning, Li Zhao, Jun Zhuang
The microstructured and hyperdoped silicon as a superior photoelectric and photovoltaic material is firstly studied as a gas-sensing material. The material is prepared by femtosecond-laser irradiation on Selenium-coated silicon and then fabricated as a conductive gas sensor targeting for ammonia. At room temperature, the sensitivity, response time, repeatability, distinguishability, selectivity, and natural aging effect of the sensor have been systematically studied. Results show that such black silicon has good potential for application as an ammonia-sensing material...
January 17, 2018: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/29336641/impact-of-forward-and-backward-scattering-and-corneal-higher-order-aberrations-on-visual-acuity-after-penetrating-keratoplasty
#5
Hidenaga Kobashi, Kazutaka Kamiya, Kimiya Shimizu
PURPOSE: To assess the relationship of forward and backward scattering and corneal higher-order aberrations (HOAs) with corrected distance visual acuity (CDVA) after penetrating keratoplasty (PK). METHODS: This retrospective study comprised 25 eyes of 25 consecutive patients who underwent PK using the VisuMax femtosecond laser system and age-matched 25 eyes of 25 healthy subjects. We quantitatively assessed objective scattering index (OSI) using the double-pass instrument (OQAS II, Visiometrics), corneal densitometry (CD) and corneal HOAs with the Scheimpflug rotating camera (Pentacam HR, Oculus) 1 year postoperatively...
January 16, 2018: Seminars in Ophthalmology
https://www.readbyqxmd.com/read/29335102/comparison-of-2-laser-fragmentation-patterns-used-in-femtosecond-laser-assisted-cataract-surgery
#6
Mehdi Shajari, Sherin Khalil, Wolfgang J Mayer, Ghada Al-Khateeb, Myriam Böhm, Kerstin Petermann, Eva Hemkeppler, Thomas Kohnen
PURPOSE: To evaluate the effect of fragmentation patterns (pie pattern versus grid pattern) on effective phacoemulsification time (EPT). SETTING: Department of Ophthalmology, Goethe University, Frankfurt am Main, Germany. DESIGN: Retrospective case series. METHODS: Eyes that had femtosecond laser-assisted cataract surgery were included. One half of the group was treated with the pie pattern. The preoperative lens density was evaluated by Scheimpflug imaging (Pentacam)...
December 2017: Journal of Cataract and Refractive Surgery
https://www.readbyqxmd.com/read/29335099/femtosecond-laser-assisted-cataract-surgeries-reported-to-the-european-registry-of-quality-outcomes-for-cataract-and-refractive-surgery-baseline-characteristics-surgical-procedure-and-outcomes
#7
Mats Lundström, Mor Dickman, Ype Henry, Sonia Manning, Paul Rosen, Marie-José Tassignon, David Young, Ulf Stenevi
PURPOSE: To describe a large cohort of femtosecond laser-assisted cataract surgeries in terms of baseline characteristics and the related outcomes. SETTING: Eighteen cataract surgery clinics in 9 European countries and Australia. DESIGN: Prospective multicenter case series. METHODS: Data on consecutive eyes having femtosecond laser-assisted cataract surgery in the participating clinics were entered in the European Registry of Quality Outcomes for Cataract and Refractive Surgery (EUREQUO)...
December 2017: Journal of Cataract and Refractive Surgery
https://www.readbyqxmd.com/read/29335098/factors-affecting-corneal-incision-position-during-femtosecond-laser-assisted-cataract-surgery
#8
Chandra Bala, Thomas Chan, Kerrie Meades
PURPOSE: To compare the expected versus actual position and dimension of corneal incisions during femtosecond laser-assisted cataract surgery. SETTING: Private Ophthalmic Clinic, Sydney, NSW, Australia. DESIGN: Retrospective case series. METHODS: Video recordings of femtosecond laser-assisted cataract surgery with a Lensx laser were reviewed. The deviation of the main and 2 secondary incisions from the expected position were correlated with globe tilt, globe displacement, and biometric data...
December 2017: Journal of Cataract and Refractive Surgery
https://www.readbyqxmd.com/read/29335093/changes-in-biomechanically-corrected-intraocular-pressure-and-dynamic-corneal-response-parameters-before-and-after-transepithelial-photorefractive-keratectomy-and-femtosecond-laser-assisted-laser-in%C3%A2-situ-keratomileusis
#9
Hun Lee, Cynthia J Roberts, Tae-Im Kim, Renato Ambrósio, Ahmed Elsheikh, David Sung Yong Kang
PURPOSE: To evaluate the changes in biomechanically corrected intraocular pressure (IOP) and new dynamic corneal response parameters measured by a dynamic Scheimpflug analyzer before and after transepithelial photorefractive keratectomy (PRK) and femtosecond laser-assisted laser in situ keratomileusis (LASIK). SETTING: Yonsei University College of Medicine and Eyereum Eye Clinic, Seoul, South Korea. DESIGN: Retrospective case series. METHODS: Medical records of patients having transepithelial PRK or femtosecond-assisted LASIK were examined...
December 2017: Journal of Cataract and Refractive Surgery
https://www.readbyqxmd.com/read/29333627/saturable-absorption-in-2d-ti3-c2-mxene-thin-films-for-passive-photonic-diodes
#10
Yongchang Dong, Sergii Chertopalov, Kathleen Maleski, Babak Anasori, Longyu Hu, Sriparna Bhattacharya, Apparao M Rao, Yury Gogotsi, Vadym N Mochalin, Ramakrishna Podila
MXenes comprise a new class of 2D transition metal carbides, nitrides, and carbonitrides that exhibit unique light-matter interactions. Recently, 2D Ti3 CNTx (Tx represents functional groups such as OH and F) was found to exhibit nonlinear saturable absorption (SA) or increased transmittance at higher light fluences, which is useful for mode locking in fiber-based femtosecond lasers. However, the fundamental origin and thickness dependence of SA behavior in MXenes remain to be understood. 2D Ti3 C2 Tx thin films of different thicknesses are fabricated using an interfacial film formation technique to systematically study their nonlinear optical properties...
January 15, 2018: Advanced Materials
https://www.readbyqxmd.com/read/29331455/femtosecond-laser-cataract-surgery-in-pediatric-patients
#11
Claudia Corredor-Ortega, Roberto Gonzalez-Salinas, María José Montero, Rocío González-Flores, Allan Collura-Merlier, Guadalupe Cervantes-Coste, Erick Mendoza-Schuster, Cecilio Velasco-Barona
No abstract text is available yet for this article.
January 10, 2018: Journal of AAPOS: the Official Publication of the American Association for Pediatric Ophthalmology and Strabismus
https://www.readbyqxmd.com/read/29328247/femtosecond-alexandrite-laser-passively-mode-locked-by-an-inp-ingap-quantum-dot-saturable-absorber
#12
Shirin Ghanbari, Ksenia A Fedorova, Andrey B Krysa, Edik U Rafailov, Arkady Major
An Alexandrite laser passively mode-locked using an InP/InGaP quantum-dot semiconductor saturable absorber mirror (QD-SESAM) was demonstrated. The laser was pumped at 532 nm and generated pulses as short as 380 fs at 775 nm with an average output power of 295 mW. To the best of our knowledge, this is the first report on a passively mode-locked femtosecond Alexandrite laser using a SESAM in general and a QD-SESAM in particular.
January 15, 2018: Optics Letters
https://www.readbyqxmd.com/read/29328212/high-throughput-microchannel-fabrication-in-fused-silica-by-temporally-shaped-femtosecond-laser-bessel-beam-assisted-chemical-etching
#13
Zhi Wang, Lan Jiang, Xiaowei Li, Andong Wang, Zhulin Yao, Kaihu Zhang, Yongfeng Lu
We proposed combining temporally shaped (double-pulse train) laser pulses with spatially shaped (Bessel beam) laser pulses. By using a temporally shaped femtosecond laser Bessel-beam-assisted chemical etching method, the energy deposition efficiency was improved by adjusting the pulse delay to yield a stronger material modification and, thus, a higher etching depth. The etching depth was enhanced by a factor of 13 using the temporally shaped Bessel beam. The mechanism of etching depth enhancement was elucidated by localized transient-free electrons dynamics-induced structural and morphological changes...
January 1, 2018: Optics Letters
https://www.readbyqxmd.com/read/29328197/fiber-bragg-grating-fabricated-in-micro-single-crystal-sapphire-fiber
#14
Shuo Yang, Daniel Homa, Gary Pickrell, Anbo Wang
This Letter introduces a fiber Bragg grating (FBG) in a micro-single-crystal sapphire fiber (micro-SFBG) for sensing applications in high-temperature and harsh environments. The FBG was fabricated by a point-by-point method via an IR-femtosecond laser in a large-diameter sapphire fiber that was then wet-hot acid etched to achieve microfiber size, which culminated in fabricating and characterizing a 9.6 μm diameter micro-SFBG. The refractive index measurement ranging from 1 to 1.75 and temperature measurement from room temperature to 1400°C are also reported...
January 1, 2018: Optics Letters
https://www.readbyqxmd.com/read/29328183/ultrafast-multipulse-damage-threshold-of-femtosecond-high-reflectors
#15
Viktória Csajbók, Zsolt Bedőházi, Benedek J Nagy, Péter Dombi
Laser-induced damage threshold is a fundamental figure of merit of femtosecond optical components used in large-scale laser systems. We tested a series of ultrafast mirrors featuring high band-gap dielectric materials as well as improved design and coating techniques. In a broad range of the damage test pulse train involving between 10 and 100,000 pulses (40 fs, 800 nm), pure dielectric high reflectors exhibit around 1.5  J/cm2 and hybrid Ag-multilayer mirrors can exhibit well above 1.2  J/cm2 damage threshold...
January 10, 2018: Applied Optics
https://www.readbyqxmd.com/read/29328173/random-fiber-laser-based-on-artificially-controlled-backscattering-fibers
#16
Xiaoliang Wang, Daru Chen, Haitao Li, Lijuan She, Qiong Wu
The random fiber laser (RFL), which is a milestone in laser physics and nonlinear optics, has attracted considerable attention recently. Most previously reported RFLs are based on distributed feedback of Rayleigh scattering amplified through the stimulated Raman-Brillouin scattering effect in single-mode fibers, which require long-distance (tens of kilometers) single-mode fibers and high threshold, up to watt level, due to the extremely small Rayleigh scattering coefficient of the fiber. We proposed and demonstrated a half-open-cavity RFL based on a segment of an artificially controlled backscattering single-mode fiber with a length of 210 m, 310 m, or 390 m...
January 10, 2018: Applied Optics
https://www.readbyqxmd.com/read/29328161/ultrafast-and-low-power-crystallization-in-ge1sb2te4-and-ge1sb4te7-thin-films-using-femtosecond-laser-pulses
#17
Smriti Sahu, Rituraj Sharma, K V Adarsh, Anbarasu Manivannan
Rapid and reversible switching between amorphous and crystalline phases of phase-change material promises to revolutionize the field of information processing with a wide range of applications including electronic, optoelectronics, and photonic memory devices. However, achieving faster crystallization is a key challenge. Here, we demonstrate femtosecond-driven transient inspection of ultrafast crystallization of as-deposited amorphous Ge1Sb2Te4 and Ge1Sb4Te7 thin films induced by a series of 120 fs laser pulses...
January 10, 2018: Applied Optics
https://www.readbyqxmd.com/read/29321454/paper-like-surface-microstructure-fabricated-on-a-polymer-surface-by-femtosecond-laser-machining
#18
Kenji Goya, Yusuke Fuchiwaki
In this study, we demonstrate the precise control of fluid flow using femtosecond (FS) laser-induced microstructures. A microgroove structure inscribed on a poly(methyl methacrylate) (PMMA) substrate functions as a superhydrophilic membrane similar to paper. We first estimated the flow rate for pure water on microgrooves fabricated at various laser fluences in the range from 9.2 to 100.8 J/cm2. The results showed that the flow rate could be tuned in the range from 0.30 to 12.07 μL/s by varying the laser irradiation parameters...
2018: Analytical Sciences: the International Journal of the Japan Society for Analytical Chemistry
https://www.readbyqxmd.com/read/29317662/shrinkable-silver-diffraction-grating-fabricated-inside-a-hydrogel-using-522-nm-femtosecond-laser
#19
Manan Machida, Yasutaka Nakajima, Maria Leilani Torres-Mapa, Dag Heinemann, Alexander Heisterkamp, Mitsuhiro Terakawa
The integration of metal microstructures and soft materials is promising for the realization of novel optical and biomedical devices owing to the flexibility and biocompatibility of the latter. Nevertheless, the fabrication of three-dimensional metal structures within a soft material is still challenging. In this study, we demonstrate the fabrication of a silver diffraction grating inside a biocompatible poly(ethylene glycol) diacrylate (PEGDA) hydrogel by using a 522-nm femtosecond laser via multi-photon photoreduction of silver ions...
January 9, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29315440/femtosecond-laser-assisted-stromal-lenticule-addition-keratoplasty-for-the-treatment-of-advanced-keratoconus-a-preliminary-study
#20
Leonardo Mastropasqua, Mario Nubile, Niccolò Salgari, Rodolfo Mastropasqua
PURPOSE: To investigate the in vivo effect of a novel femtosecond laser-assisted procedure termed stromal lenticule addition keratoplasty for advanced keratoconus. METHODS: Ten patients with stage III and IV stable keratoconus were included. Negative meniscus-shaped stromal lenticules were produced from corneoscleral eye bank buttons with a refractive lenticule extraction procedure with a 500-kHz VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany). Recipient corneas underwent a modified femtosecond laser flap-cut procedure to produce an intrastromal pocket and lenticules were implanted...
January 1, 2018: Journal of Refractive Surgery
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