Podcasts about femtosecond laser

Femtosecond Laser Assisted Cataract Surgery (FLACS) has been around for over a decade, yet there isn't necessarily consensus amongst the eye care community as to how this technology should be implemented within cataract surgery. Some advocate strongly for FLACS, citing greater reliability and precision than traditional cataract surgery. Others have argued, however, that even if the femtosecond technology has improved accuracy, this doesn't necessarily mean that it translates to better cataract surgery results. Dr. Eric Donnenfeld joins the podcast.

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.07.02.547378v1?rss=1 Authors: Tang, S. Abstract: We present a simplified femtosecond laser frequency divider designed to divide the repetition frequency of an 80 MHz laser pulse into a 40 MHz laser pulse using a resonant model Pockels cell. The simplified driving electronics include a commercially obtainable frequency divider, power amplifier and impedance transformer, which can be easily assembled in a laboratory. By simply integrating this device into a conventional two-photon imaging system, we observed a two-fold increase in two-photon excitation efficiency and imaging intensity, while maintaining the same average excitation laser power. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.01.10.523473v1?rss=1 Authors: Bosch, C., Lindenau, J., Pacureanu, A., Peddie, C. J., Majkut, M., Douglas, A. C., Carzaniga, R., Rack, A., Collinson, L., Schaefer, A., Stegmann, H. Abstract: Correlative multimodal imaging is a useful approach to investigate complex structural relations in life sciences across multiple scales. For these experiments, sample preparation workflows that are compatible with multiple imaging techniques must be established. In one such implementation, a fluorescently-labelled region of interest in a biological soft tissue sample can be imaged with light microscopy before staining the specimen with heavy metals, enabling follow-up higher resolution structural imaging at the targeted location, bringing context where it is required. Alternatively, or in addition to fluorescence imaging, other microscopy methods such as synchrotron X-ray computed tomography with propagation-based phase contrast (SXRT) or serial blockface scanning electron microscopy (SBF-SEM) might also be applied. When combining imaging techniques across scales, it is common that a volumetric region of interest (ROI) needs to be carved from the total sample volume before high resolution imaging with a subsequent technique can be performed. In these situations, the overall success of the correlative workflow depends on the precise targeting of the ROI and the trimming of the sample down to a suitable dimension and geometry for downstream imaging. Here we showcase the utility of a novel femtosecond laser device to prepare microscopic samples (1) of an optimised geometry for synchrotron X-ray microscopy as well as (2) for subsequent volume electron microscopy applications, embedded in a wider correlative multimodal imaging workflow (Fig. 1). Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Factors Affecting Corneal Incision Position During Femtosecond Laser-assisted Cataract Surgery Dr Kerrie Meades was the first female ophthalmologist to perform laser vision correct in Australia. In this podcast, Dr Meades discusses the article Factors affecting corneal incision position during femtosecond laser-assisted cataract surgery. Dr Meades was prompted to explore this topic due to a lack of precision from laser for the second incision. Tilt and displacement can affect the translation of the program of the laser and the actual incision. As such, OCT guidance is needed for the secondary incision, as you do for the primary incision. Dr Meades provides an insight into how patient behaviour and anatomy can affect docking, and therefore incisions.View article here

Surendra Basti, MD and Robert Feder, MD offer the latest updates on Femtosecond Laser Cataract Surgery. They discuss and debate the controversy around this approach and what factors are part of this controversy. They share if there is a clear medical criterion for one procedure over the other, the latest research and what the Department of Ophthalmology at Northwestern Medicine offers in terms of FLCS.

Dr Preeya Gupta and Dr. Gary Wortz discuss the importance of managing low levels of corneal astigmatism and how your refractive outcomes rely on this. They review their success with using the femtosecond laser for arcuate incisions, and discuss the in's and out's of a novel Femto LRI nomogram available at www.lricalc.com

Dr. Keith Walter and Dr. Gary Wortz discuss why Femto is beneficial in 2020, how they have been very successful in integrating Femto into their busy practices, and their most common use for the Femtosecond laser.

Mark A. Rolain, MD

Ultrafast laser spectroscopy is commonly used to study dynamical processes happen in the time scale of femtoseconds (10-15 s) to picoseconds (10-12 s). When probing complex systems with many degrees of freedom, however the 1D spectrum is usually congested with contributions from many structural components. Multidimensional coherent spectroscopy is a way to overcome this problem by spreading the spectral information in two or more frequency axes. In this part, I will focus on two-dimensional (2D) laser spectroscopy which can provide an incisive tool to probe the electronic transitions, and energetic evolutions in ultrafast time scales. I will demonstrate its application to the study of organic dye Coumarin 102. This 2D spectroscopy method could monitor the energy level broadening and observe time evolution. This dynamic information will help to determine the energy and charge transfer pathways in molecular systems. In biomedical research intravital two-photon fluorescence microscopy has provided insightful information on dynamic processes in vivo. However the use of exogenous labeling agents limits its applications. I will first demonstrate in vivo mouse mast cells imaging using endogenous tryptophan as the fluorophore for immunological research. Laser beam scanning is required in most current two-photon microscopes to achieve 2D images. Based on temporal focusing of femtosecond laser pulses a new type of two-photon microscope can achieve 2D images without scanning the laser beam; therefore it could reach hundreds frames/second imaging speed. To acquire depth information, most modalities still need to move the sample stage mechanically. In temporal focusing two-photon microscope changing the group velocity dispersion of the femtosecond laser pulses could lead to the displacement of the plane of the temporal focus along the optical axis from the geometrical focus of the objective lens, yielding z-scanning as a function of dispersion. Currently my group is developing pulse shaping technique with spatial light modulators (e.g. acousto-opto modulators) to electronically control the dispersion of the femtosecond laser pulses in spectral domain to achieve fast 3D fluorescence imaging.

Guest: Gerard Sutton, MBBS MD FRANZCO Sydney Medical School Foundation Professor of Corneal and Refractive Surgery Save Sight Institute, Sydney University Vision Eye Institute Sydney, Australia

Guest: Gerard Sutton, MBBS MD FRANZCO Sydney Medical School Foundation Professor of Corneal and Refractive Surgery Save Sight Institute, Sydney University Vision Eye Institute Sydney, Australia

Presented by Michel Meunier, Professor, Department of Engineering Physics, Ecole Polytechnique de Montreal.

A conversation between Lisa B. Arbisser, MD, and Wayne Knox, PhD. Dr. Lisa Arbisser talks with Wayne Knox, professor of optics at the University of Rochester. Dr. Knox shares his experience with the latest experimental use of the femtosecond laser, using the laser to adjust the power of an IOL after it has been implanted in the eye. Unlike the light adjustable lens, this noninvasive technique of shaping the refractive index could be used on standard acrylic hydrophobic IOLs to correct for residual refractive errors, astigmatism, and higher order aberrations. It may even be used to produce multifocality on the lens after implantation. (January 2012)

An interview with David Hardten, MD. Dr. David Hardten, program director for the 2011 Refractive Surgery Subspecialty Day, discusses the highlights of this ISRS-sponsored Annual Meeting, including hotly debated topics on detecting forme fruste keratoconus and wave-front guided ablation, updates on corneal cross-linking and presbyopia correction as well as advice on using femtosecond lasers for astigmatic keratotomy. (November 2011)

Eric Mazur, the Dean of Applied Physics at Harvard University, delivers a lecture entitled, Stopping Time. In it he breaks time down into it's smallest measureable components via photography and developments in laser technology.

Eric Mazur, the Dean of Applied Physics at Harvard University, delivers a lecture entitled, Stopping Time. In it he breaks time down into it's smallest measureable components via photography and developments in laser technology.

Eric Mazur, the Dean of Applied Physics at Harvard University, delivers a lecture entitled, Stopping Time. In it he breaks time down into it's smallest measureable components via photography and developments in laser technology.

A conversation among Richard Lindstrom, MD, David F. Chang, MD, William W. Culbertson, MD, and Michael C. Knorz, MD. Dr. Richard Lindstrom moderates a panel of 3 experts who share their impressions on LASIK-assisted cataract surgery. The participants discuss the current and potential benefits of applying Femtosecond laser to the cataract procedure, including precise control of the size and location of the capsulorrhexis, an integrated imaging system, reproducible incisions for astigmatism correction, and the ability to soften or prechop a dense nucleus. (May 2011)

The generation of coherent high-order harmonics from the interaction of ultra-intense femtosecond laser pulses with solid density plasmas holds the promise for table-top sources of intense extreme ultraviolet (XUV) and soft x-ray (SXR) radiation. Furthermore, they give rise to the prospect of combining the attosecond pulse duration of conventional gas-harmonic sources with the photon flux currently only available from large-scale free-electron laser or synchrotron facilities. In this thesis a series of experiments studying various aspects of harmonic generation from such a plasma source are presented and the emitted XUV-radiation is characterized spectrally, spatially and temporally. The measurements probe the dynamics of the plasma surface on a sub-laser-cycle time scale and help to increase our understanding of the harmonic generation process. It is shown that, at moderate intensities and laser contrast, the emitted harmonics are indeed phase-locked but chirped and emitted as a train of XUV-bursts of attosecond duration. Measurements with very high contrast relativistically intense driving pulses reveal the generation of harmonics up to the relativistic cutoff in a diffraction-limited beam with constant divergence observed for all wavelength. This implies that the harmonics are generated on a curved surface and travel through a focus after the target possibly opening a route towards extreme intensities in the process. In addition it is found that a target roughness on the scale of the wavelength of the highest generated harmonic does not adversely affect the harmonic beam quality implying that the generation of diffraction-limited keV-harmonic beams should be possible. In a third set of experiments the first demonstration of harmonic generation from solid targets using an 8 fs driving laser opens a route towards the generation of ultra-intense single-as pulses and gives conclusive evidence for the unequal spacing of the harmonic emission. Based on these results the development of ultra-intense sources of single as-pulses from the interaction of intense laser pulses with solid surfaces could advance at a fast pace making XUV-pump XUV-probe type investigations of nonlinear processes with attosecond time resolution feasible in the near future.

Guest: Shahzad Mian, MDAsstant ProfessorResidency DirectorDirector of Refractive SurgeryKellogg Eye CenterUniversity of MichiganAnn Arbor, MI

In the course of this work a new technique to measure the frequency of light has been developed, implemented and refined. For all time and frequency measurements the SI second defined by the cesium ground state hyperfine splitting near 9.2 GHz is the defined standard of reference. Therefore in precision optical frequency measurements optical frequencies on the order of several 100 THz – too fast to be counted with any electronics – have to be compared with radio frequencies on the order of a few GHz. The basic idea here is to measure dierences between optical frequencies with the help of frequency combs generated by the periodic pulse trains of femtosecond lasers. The output spectrum of such a laser consists of modes equally spaced by the repetition frequency of the pulses and forms a convenient ruler in frequency space. Extending this principle to the intervals between harmonics of the same optical frequency f, in the most simple case the interval between f and 2f, allows the absolute measurement of an optical frequency f = 2f − f. To bridge the interval between an optical frequency f and its second harmonic 2f a broad frequency comb with a width of several 100 THz is needed. This can be achieved with very short pulses (on the order of 5 fs) or with moderately short pulses on the order of a few 10 fs via self phase modulation in an optical fiber. Especially suited for such massive broadening are so called photonic crystal fibers. Here the light is guided in a very small core (1-2 µm) surrounded by air holes. This development culminates in the “single laser frequency chain” linking the radio frequency domain with the optical domain with the help of just one fs laser, a piece of fiber and some optics. Our optical frequency synthesizer can be used to measure not only one but almost any optical frequency with the same compact apparatus. Originally this project has been initiated to perform precision spectroscopy on the 1S- 2S transition in atomic hydrogen, a project with a long tradition in our group, and yielded what is thus far the most precise optical frequency measurement with a relative uncertainty of 1.8×10−14. Hydrogen as the most simple bound system served and still serves as an important cornerstone for tests of quantum physics, the measurement of the 1S Lamb shift represents one of the most accurate QED tests. Furthermore the Rydberg constant can be determined very precisely from optical frequency measurements in hydrogen. Soon it became obvious that this technique has a broad applicability. In this work transition frequencies in cesium, indium and molecular iodine have been measured. Besides that principle tests on this technique have been conducted. The direct comparison of two such frequency chains showed agreement on the level of 5 × 10−16. Further applications besides precision spectroscopy can be found in the time domain. There it is now possible with this technique to control the phase evolution of ultra short light pulses and perform optical waveform synthesis. As optical clock work for future all optical clocks a fs frequency chain transfers stability and accuracy from the optical to the rf domain.