Recent Developments In Laser Technology Research Articles

Elucidating fungal decomposition of organic matter at sub-micrometer spatial scales using optical photothermal infrared (O-PTIR) microspectroscopy.

In microbiological studies, a common goal is to link environmental factors to microbial activities. Both environmental factors and microbial activities are typically derived from bulk samples. It is becoming increasingly clear that such bulk environmental parameters poorly represent the microscale environments microorganisms experience. Using infrared (IR) microspectroscopy, the spatial distribution of chemical compound classes can be visualized, making it a useful tool for studying the interactions between microbial cells and their microenvironments. The spatial resolution of conventional IR microspectroscopy has been limited by the diffraction limit of IR light. The recent development of optical photothermal infrared (O-PTIR) microspectroscopy has pushed the spatial resolution of IR microspectroscopy beyond this diffraction limit, allowing the distribution of chemical compound classes to be visualized at sub-micrometer spatial scales. To examine the potential and limitations of O-PTIR microspectroscopy to probe the interactions between fungal cells and their immediate environments, we imaged the decomposition of cellulose films by cells of the ectomycorrhizal fungus Paxillus involutus and compared O-PTIR results using conventional IR microspectroscopy. Whereas the data collected with conventional IR microspectroscopy indicated that P. involutus has only a very limited ability to decompose cellulose films, O-PTIR data suggested that the ability of P. involutus to decompose cellulose was substantial. Moreover, the O-PTIR method enabled the identification of a zone located outside the fungal hyphae where the cellulose was decomposed by oxidation. We conclude that O-PTIR can provide valuable new insights into the abilities and mechanisms by which microorganisms interact with their surrounding environments.IMPORTANCEInfrared (IR) microspectroscopy allows the spatial distribution of chemical compound classes to be visualized. The use of conventional IR microspectroscopy in microbiological studies has been restricted by limited spatial resolution. Recent developments in laser technology have enabled a new class of IR microspectroscopy instruments to be developed, pushing the spatial resolution beyond the diffraction limit of IR light to approximately 500 nm. This improved spatial resolution now allows microscopic observations of changes in chemical compounds to be made, making IR microspectroscopy a useful tool to investigate microscale changes in chemistry that are caused by microbial activity. We show these new possibilities using optical photothermal infrared microspectroscopy to visualize the changes in cellulose substrates caused by oxidation by the ectomycorrhizal fungus Paxillus involutus at the interface between individual fungal hyphae and cellulose substrates.

Analytical challenges of glycosaminoglycans at biological interfaces

The analysis of glycosaminoglycans (GAGs) is a challenging task due to their high structural heterogeneity, which results in diverse GAG chains with similar chemical properties. Simultaneously, it is of high importance to understand their role and behavior in biological systems. It has been known for decades now that GAGs can interact with lipid molecules and thus contribute to the onset of atherosclerosis, but their interactions at and with biological interfaces, such as the cell membrane, are yet to be revealed. Here, analytical approaches that could yield important knowledge on the GAG-cell membrane interactions as well as the synthetic and analytical advances that make their study possible are discussed. Due to recent developments in laser technology, we particularly focus on nonlinear spectroscopic methods, especially vibrational sum-frequency generation spectroscopy, which has the potential to unravel the structural complexity of heterogeneous biological interfaces in contact with GAGs, in situ and in real time.Graphical abstract

Parametric Study of Laser Welding on Polyamide using Design of Experiments

Laser welding was primarily employed for metals but recent developments in laser technology have enabled its applications in the polymers field. Laser transmission welding or joining of two polymers and metal-polymer has become feasible. The study was mainly aimed to investigate the influence of laser power, speed of welding, and number of passes based on Taguchi orthogonal array on responses by using continuous mode high power diode fiber laser on polyamide. The weld quality was assessed by measuring the strength of weld and width of the weld seam. Initial study on diode fiber laser welding machine and the parameters associated with it was essential to design the experimental layout. Polyamide, which is widely used in the automotive industry was selected as the material and the influence of various parameters on the laser welds were studied using design of experiments. The experimental studies were performed based on orthogonal array method. The responses of the weld were measured using an optical metallurgical microscope. The ideal parameters for maximum joint strength and minimum weld width are investigated using Taguchi method. The multi-objective optimization has been done by applying grey relational analysis to identify the levels of factors that result in the maximum strength and minimum weld seam width.

First-principles calculations for attosecond electron dynamics in solids

Nonequilibrium electron dynamics in solids is an important subject from both fundamental and technological points of view. The recent development of laser technology has enabled us to study ultrafast electron dynamics in the time domain. First-principles calculation is a powerful tool for analyzing such complex electron dynamics and clarifying the physics behind the experimental observation. In this article, we review the recent development of the first-principles calculation for light-induced electron dynamics in solids by revising its application to recent attosecond experiments. The electron dynamics calculations offer an accurate description of static and transient optical properties of solids and provide physics insight into light-induced electron dynamics. Furthermore, the microscopic decomposition of transient properties of nonequilibrium systems has been developed to extract microscopic information from the simulation results. The first-principles analysis opened a novel path to analyze the nonequilibrium electron dynamics in matter and to provide the fundamental understanding complementarily with the sophisticated experimental technique.

Gamma photons and electron-positron pairs from ultra-intense laser-matter interaction: A comparative study of proposed configurations

High-energy γ-photon generation via nonlinear Compton scattering and electron–positron pair creation via the Breit–Wheeler process driven by laser–plasma interaction are modeled, and a number of mechanisms are proposed. Owing to the small cross section, these processes require both an ultra-intense laser field and a relativistic electron bunch. The extreme conditions for such scenarios can be achieved through recent developments in laser technology. Photon emission via nonlinear Thomson and Compton scattering has been observed experimentally. High-energy positron beams generated via a multiphoton process have recently been observed too. This paper reviews the principles of γ-ray emission and e+e− pair creation in the context of laser–plasma interaction. Several proposed experimental setups for γ-ray emission and e+e− pair creation by ultra-intense laser pulses are compared in terms of their efficiency and the quality of the γ-photon and positron beams produced for ultrashort (15 fs) and longer (150 fs) multi-petawatt laser beams.

Visual Outcomes and Higher Order Aberrations Following LASIK on Eyes with Low Myopia and Astigmatism.

Background:Laser-Assisted in situ Keratomileusis (LASIK) can induce corneal aberrations that can impact vision and patient satisfaction. Recent developments in laser technologies have helped minimise these aberrations.Objective:To assess the quality of vision and change in Higher-Order Aberrations (HOAs) following wavefront-optimized LASIK in low-myopic astigmatic patients.Methods:LASIK was performed on a total of 76 eyes in patients with myopia <4.0 D and cylinder <2.0 D using the WaveLight® EX500 excimer and FS200 femtosecond laser platform. Visual acuity, contrast sensitivity and HOAs were measured at 1 and 3 months postoperatively and compared to preoperative values. Subjective quality of vision was assessed pre- and postoperatively using a VF14 questionnaire.Results:Mean postoperative Spherical Equivalent (SE) was -0.09 ± 0.26 µm with 95% of patients within ± 0.5 D of attempted SE. Postoperative uncorrected distance visual acuity was 20/20 or better for 96% of patients. Contrast sensitivity increased against horizontal and vertical gratings at all spatial frequencies except for vertical gratings at 18 cycles/degree. Spherical aberration and total HOA increased by 0.085 µm and 0.13 µm respectively. The mean VF14 score increased from 89.2 ± 16.7% to 99 ± 1.4% postoperatively.Conclusion:LASIK performed using the WaveLight® EX500 excimer and WaveLight® FS200 laser platform provided improved contrast sensitivity and visual acuity with minimal introduction of HOAs, making it a suitable platform for low myopic astigmatic patients.

Laser-driven ion acceleration: methods, challenges and prospects

The recent development of laser technology has resulted in the construction of short-pulse lasers capable of generating fs light pulses with PW powers and intensities exceeding 1021 W/cm2, and has laid the basis for the multi-PW lasers, just being built in Europe, that will produce fs pulses of ultra-relativistic intensities ~ 1023 – 1024 W/cm2. The interaction of such an intense laser pulse with a dense target can result in the generation of collimated beams of ions of multi-MeV to GeV energies of sub-ps time durations and of extremely high beam intensities and ion fluencies, barely attainable with conventional RF-driven accelerators. Ion beams with such unique features have the potential for application in various fields of scientific research as well as in medical and technological developments. This paper provides a brief review of state-of-the art in laser-driven ion acceleration, with a focus on basic ion acceleration mechanisms and the production of ultra-intense ion beams. The challenges facing laser-driven ion acceleration studies, in particular those connected with potential applications of laser-accelerated ion beams, are also discussed.

Pair production from space- and time-dependent strong fields

The recent development of laser technology and the large number of extreme laser experiments under construction renewed the research related to pair production in strong fields. If the predicted threshold of nonlinear QED is reached, pair production may be observed and the measurements must be compared with appropriate theoretical predictions. However the theoretical side still lacks the understanding of the relevant quantum processes including the effect of laser field parameters on the number and spectrum of created particles. We use the Dirac-Heisenberg-Wigner formalism to investigate the role of the pure electric inhomogeneity on the spectra of created pairs. This simplified model may also be relevant in high energy physics for the description of string fragmentation in the early stages of heavy ion collisions.

Photoacoustic radiation force on a microbubble.

We investigate the radiation force on a microbubble due to the photoacoustic wave which is generated by using a pulsed laser. In particular, we focus on the dependence of pulsed laser parameters on the radiation force. In order to do so, we first obtain a new and comprehensive analytical solution to the photoacoustic wave equation based on the Fourier transform for various absorption profiles. Then, we write an expression of the radiation force containing explicit laser parameters, pulse duration, and beamwidth of the laser. Furthermore, we calculate the primary radiation force acting on a microbubble. We show that laser parameters and the position of the microbubble relative to a photoacoustic source have a considerable effect on the primary radiation force. By means of recent developments in laser technologies that render tunability of pulse duration and repetition frequency possible, an adjustable radiation force can be applied to microbubbles. High spatial control of applied force is ensured on account of smaller focal spots achievable by focused optics. In this context, conventional piezoelectric acoustic source applications could be surpassed. In addition, it is possible to increase the radiation force by making source wavelength with the absorption peak of absorber concurrent. The application of photoacoustic radiation force can open a cache of opportunities such as manipulation of microbubbles used as contrast agents and as carrier vehicles for drugs and genes with a desired force along with in vivo applications.

高功率激光元件

Before going into the background of challenges imposed by modern laser technology on coated optical components, this letter reviews the major aspects of coating production and control. Current deposition techniques and characterisation methods for high power optical components applied in modern laser systems are summarised and discussed. In this context, methods are considered especially for the precise control of the spectral transfer properties of optical coatings during production. Also, a short review is presented regarding laser damage in optical coatings and the corresponding measurement techniques. In addition, the outlook includes recent developments in laser technology and corresponding trends in thin film production. OCIS codes: 140.0140, 310.1860, 310.6860, 310.3840, 140.3330. doi: 10.3788/COL201008S1.0140. Since the first demonstration of the laser principle at optical wavelengths in 1960, laser development has been one of the major pacemakers for the progress in production of optical laser components. Important steps in the fabrication of optical components involve the preparation of the bulk substrate material, the polishing of the optical surface, and finally, the deposition of a coating system governing the optical functioning of the component. In most applications, the optical coating system can be identified as the weakest link in the quality chain, which has to be optimized for the reliable performance of the component. As a consequence, the study of high power laser components is mainly concentrated on optical coatings and their precise characterisation. In the course of enormous improvements of laser output power and beam parameters, ever-increasing demands are imposed on optical coatings with respect to quality, stability, and precision. The present article is dedicated to these three major challenges and to recent progresses in the fields of optical coating, production, and quality control, as well as the optimization of the power handling capability of laser components. A brief review on modern trends in laser technology and on approaches in thin film technology to accomplish the corresponding prospective tasks is also presented.

Review of laser nanomachining

Lasers are widely used for macro- and micromachining applications in numerous industries such as automotive, electronics, and medical manufacturing. However, there are many challenges encountered in the utilization of lasers for nanomachining. The most critical requirement is that the diffraction limit of laser light must be overcome. With recent developments in laser technology in terms of short-wavelength and ultrashort pulse width, there is a wealth of opportunities to beat the diffraction limit for nanomachining of structures, devices, and materials. In this review paper, first the state-of-the-art lasers are examined from the perspective of the requirements of nanomachining. Second, a set of both serial and parallel types of laser-based, “top-down” nanomachining methods is described. Third, preliminary results obtained in our laboratory of the most recent, novel approach involving surface plasmon polaritons for the potential of massively parallel nanomachining are presented. Finally, the potential of lasers for cost-effective nanomanufacturing is assessed.

Toward control of point defects in lithium fluoride thin layers

AbstractPoint defect formation and stabilization properties, as well as their peculiar spectroscopic characteristics, locally modify the optical properties of insulating materials. Thin layers containing high concentrations of colour centres, hosted in a LiF single crystal and/or a polycrystalline matrix, offer the opportunity to develop innovative light‐emitting photonic devices. Control of all the critical parameters should be required on spatial dimension comparable with the optical wavelengths. Recent developments in laser technologies, electron and particles beam methods, and novel photon sources, have opened a wide range of opportunities. An overview of the most significant advances in this field is provided, with particular emphasis on colour‐centre LiF‐based innovative miniaturised light sources, optical amplifiers and lasers. (© 2007 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Laser ablation ICP—MS — a new dating tool in Earth science

Laser ablation inductively coupled plasma mass spectrometry (LA ICP—MS) is a newly established technique that is capable of in-situ U(Th)—Pb dating of accessory minerals in a wide range of rock types and geological environments. Recent developments in laser technology and mass spectrometry have led to substantial improvements in precision and accuracy of isotopic ages obtained by LA ICP-MS. Despite the advancements in technology, the precision and accuracy of U(Th)—Pb laser ablation ICP-MS dating are still limited by laser-induced elemental fractionation of Pb and U. This paper reviews the technique's history and summarizes recent achievements and possible future developments of this novel dating method.

Electronically induced surface chemistry: localised bond breaking versus delocalisation

AbstractSurface photochemistry can be considerably different from the corresponding molecular photochemistry. This is due to the fact that bonding of reactants to a surface induces modifications also in reaction paths via electronically excited states. These changes are of importance in respect of both fundamental and applied research. The past 40 years have seen the development of quite detailed understanding of the underlying effects, in particular in the case of bond breaking, which shows up by desorption of neutral and charged molecules and/or fragments. Recent developments in laser technology and nanostructuring have brought renewed interest to this field. Here a survey is given of the important facts and ideas in this realm. It will be argued that the counterplay between localisation of excitations and their delocalisation by coupling is the decisive effect to be understood. Copyright © 2006 John Wiley &amp; Sons, Ltd.

Clinical effect of combined treatment by subgingival curettage and CO2 laser application

Recent development of laser technology suggests a great deal of possibilities in the field of dentistry. The mechanism and safety of laser surgery is well established in many studies especially on the soft tissue applications. It has advantages including excellent hemostasis, visibility and less postoperative pain(claimed but undocumented)1,2. But from a periodontal point of view, much has yet to be proven. Several researchers have reported studies on laser applications to periodontal therapy. Cobb et al.3 and Ando et al.4 examined the in vivo bactericidal effect and concluded that the exposure of the root surface to laser could significantly decrease the levels of subgingival microflora of the patients with generalized adult periodontitis. Some studies have reported that the laser could reduce the number of curette strokes necessary for removing calculus5·Ito et al.6 reported that the laser irradiation effectively removed the smear layer, uncovered dentinal tubules, and exposed collagen fibers on the root surface. Many studies have also suggested efficacy of CO2 laser application on the root surfaces in vitro. There was an in vitro study which described the effectiveness of CO2 laser irradiation on the root surfaces removing the smear layer which could impede soft tissue attachment7. Crespi et al.8 found that more fibroblasts attached onto root surfaces CO2 laser applied in vitro. The objective of the present study was to evaluate the clinical effect of CO2 laser treatment when used in combination with conventional subgingival curettage through the measurement of clinical parameters.

Application of the 980-nm diode laser in stereotaxic surgery

With recent developments in laser technology, diode laser and optical delivery systems have become highly promising surgical devices with advantages of lower cost and higher precision. The aim of the study was to test the 980-nm diode laser for its potential use in stereotaxic surgery. In our dosimetric study, the response of cortical tissue to different energy levels of laser irradiation was investigated with different exposure durations. In vivo stereotaxic neurosurgical procedure was performed on female Wistar rats weighing 180 to 220 gr. In order to investigate the lesioning effects of the 980-nm diode laser as a function of pulse duration, laser power was adjusted to 2.0 and 3.0 W with exposure times ranging from 1.3 to 3.0 s resulting in an irradiance of 5.97 to 17.91 J/mm/sup 2/. Histologic investigation of brain specimens indicated that the 980-nm diode laser has the potential to create lesions in stereotaxic surgery. With proper selection of power level and exposure duration, target tissues could be evaporated and/or coagulated. We found the 980-nm diode laser a promising tool for neurosurgical applications.

Effective neutron targets

Because of the lack of a free neutron target, deuterium targets have been used extensively in studying the neutron structure. The unique spin structure of the 3He ground state wave function and the recent developments in laser technologies made polarized 3He targets widely used in many experiments from neutron electromagnetic from factor studies to nucleon spin structure function measurements at all major electron accelerator facilities. In this talk, the current status of the polarized 3He targets will be reviewed. I will focus on neutron electromagnetic form factor studies using polarized 3He targets. The polarized nucleon spin structure function measurements using polarized 3He targets will also be discussed.

Raman spectroscopy in undergraduate chemical education

Raman spectroscopy is one of the underutilized techniques in undergraduate chemical education. Recent developments in laser technology and its applications to Raman instrumentation have made Raman an extremely useful and powerful analytical tool. The article describes some of the applications of Raman in teaching chemistry at the undergraduate level.

Lasers in dermatology.

Lasers have many applications in dermatology. Recent developments in laser technology have produced significant therapeutic advances in several areas. The introduction of pulsed tunable dye lasers has considerably improved the treatment of vascular lesions, particularly port wine stain malformations in children. A wider range of continuous-wave and quasi-continuous-wave lasers have also become available for treating vascular lesions, and their use in conjunction with automated delivery systems has improved results whilst reducing adverse effects. Increasing interest in treatment of pigmented lesions and tattoos has led to investigation of a range of high-power short-pulse lasers, and early results look very promising. However, further work is needed in all these areas to determine which lesions respond best to each laser system, and which treatment techniques are optimal.

Laser Spectroscopy

A seminar-in-depth on the Impact of Lasers in Spectroscopy was featured at the SPIE 18th Annual Meeting in San Diego in August, 1974. The overall intent of the seminar was to review the current state-of-the-art and the future of laser spectroscopy with emphasis on recent developments in laser technology and on the impact of the laser on spectroscopic methods and applications. Moreover, the seminar was designed to provide an environment where practical applications of laser spectroscopy could be discussed, reviewed, and evaluated.