Advances In Laser Technology Research Articles

Spatially resolved online particle detector using scintillators for laser-driven particle sources.

Laser-based particle accelerators have been an active field of research for over two decades moving from laser systems capable of one shot every hour to systems able to deliver repetition rates in the Hz regime. Based on the advancements in laser technology, the corresponding detection methods need to develop from single to multiple use with high readout speed. Here, we present an online compact trackerof particles using scintillators with nine resolvable energy levels and a spatial resolution of 3.6 × 3.6mm2 over the whole active area. This paper describes the designand construction of the detector, which is based on pixellated scintillators embedded inside an absorber matrix. The scintillator pixels are fiberoptically coupled to a camera system for online readout and analysis. Calibration with a radioactive source and first experimental data measuring laser accelerated ions at the PHELIX laser at GSI, Darmstadt, Germany, are presented and discussed.

Advanced Laser Technology for Quantum Communications (Tutorial Review)

AbstractQuantum communications is the art of exchanging and manipulating information beyond the capabilities of the conventional technologies using the laws of quantum mechanics. With applications ranging from quantum computing to cryptographic systems with information‐theoretic security, there is strong incentive to introduce quantum communications into many areas of the society. However, an important challenge is to develop viable technologies meeting the stringent requirements of low noise and high coherence for quantum state encoding, of high bit rate and low power for the integration with classical communication networks, and of scalable and low‐cost production for a practical wide‐deployment. This tutorial presents recent advances in laser modulation technologies that have enabled the development of efficient and versatile light sources for quantum communications, with a particular focus on quantum key distribution (QKD). Such approaches have been successfully used to demonstrate several QKD protocols with state‐of‐the‐art performance. The applications and experimental results are reviewed and interpreted in the light of a complete theoretical background, allowing the reader to model and simulate such sources.

Elastic electron-proton scattering in the presence of a circularly polarized laser field

Owing to recent advances in laser technology, it has become important to investigate fundamental laser-assisted processes in very powerful laser fields. In the present work and within the framework of laser-assisted quantum electrodynamics, electron-proton scattering was considered in the presence of a strong electromagnetic field of circular polarization. First, we present a study of the process where we only take into account the relativistic dressing of the electron without the proton. Then, in order to explore the effect of the proton dressing, we fully consider the relativistic dressing of the electron and the proton together and describe them by using Dirac–Volkov functions. The analytical expression for the differential cross section (DCS) in both cases is derived at lowest-order of perturbation theory. As a result, the DCS is notably reduced by the laser field. It is found that the effect of proton dressing begins to appear at laser field strengths greater than or equal to 1010 V cm−1 and it therefore must be taken into account. The influence of the laser field strength and frequency on the DCS is reported. A comparison with the Mott scattering and the laser-free results is also included.

An Analytical Expression Of The Photoacoustic Signal For A Pulsed Laser With A Sinusoidal Radial Profile

Photoacoustic signal depends on several laser factors, particularly the pulse duration, energy, wavelength, beam-width and repetition rate of the pulsed laser. Although these dependencies are well tested through experiments, they can also be investigated via theoretical approaches for the research into photoacoustic signal generation in parallel to advances in laser technologies. In this study, the photoacustic signal is presented analytically by solving the photoacoustic wave equation for an optical absorber heated up by a pulsed laser. The spatial and temporal parts of the pulsed laser are modeled by a sampling (sinc) function and a Gaussian function, respectively. The radial profile obtained experimentally by using a spatial light modulator can be modeled accurately with a sampling function. Pulsed lasers can lead to nonlinear effects. This nonlinear mechanism has various advantageous for the photoacoustic imaging. These short pulsed lasers have a close-to-sinusoidal variation in the central pulse region so that the spatial part of the laser is modeled by a sampling function in this work. For the photoacoustic wave, a detailed expression is obtained analytically in terms of the pulse duration and beam-width. The photoacoustic signal is observed in terms of time for various detector positions. Moreover, a detailed analysis is conducted to obtain a correlation between the photoacoustic signal and the laser factors. Therefore, the resulting quantification of the physical laser factors can offer a useful theoretical guide for the applications of photoacoustics. The sampling modeling presented by this study can also be helpful for the understanding of the nonlinear mechanism in photoacoustics.

Laser enucleation for prostates larger than 100 mL: Comparison of HoLEP and ThuLEP.

Recently, with the advancements in laser technology, Holmium laser enucleation of the prostate (HoLEP) and Thulium laser enucleation of the prostate (ThuLEP) have come to the fore in the surgical treatment of benign prostatic hyperplasia (BPH). We aimed to evaluate and compare the outcomes of HoLEP and ThuLEP in patients with >100ml prostate volume. Patients who underwent HoLEP and ThuLEP between July 2017 and March 2020 were reviewed retrospectively. The patients were divided into two groups as HoLEP (Group 1, n=121) and ThuLEP (Group 2, n=104). Perioperative parameters, functional outcomes, continence status, intra and post-operative complications were compared between groups in the post-operative 1st and 6th month. No significant difference was found in terms of total laser energy (TLE), morcellation efficiency (ME), enucleated tissue weight (ETW), complication rates (CR) and continence status of patients between both groups (p>.05). In favour of ThuLEP group, there were statistically significant differences regarding total operation time (TOT), laser efficiency (LE), enucleation time (ET) and enucleation efficiency (EE) between groups (p≤.05). HoLEP and ThuLEP can be used safely and effectively in prostates larger than 100ml.

Same-Day Discharge Following Holmium Laser Enucleation in Patients Assessed to Have Large Gland Prostates (≥175 cc).

Background: Holmium laser enucleation of the prostate (HoLEP) is a highly effective and durable minimally invasive surgery for benign prostatic hyperplasia. Historically, alternative treatments for large glands (≥175 cc) are associated with prolonged length of stay (LOS) and postoperative catheterization. However, advances in laser technology combined with surgical technique optimization have early evidence supporting same-day discharge. We look to examine contemporary same-day discharge outcomes for large glands. Materials and Methods: With Institutional Review Board (IRB) approval we queried our electronic medical record and retrospective clinical registry to examine perioperative outcomes of large gland (≥175 cc) prostates that underwent HoLEP with consideration for same-day discharge. Results: From December 10, 2019 to September 29, 2020 we identified 55 patients with a preoperative prostate size ≥175 cc (39 CT, 12 MRI, 4 transrectal ultrasound), of which 45 were scheduled for same-day discharge and 10 for admission. Mean preoperative prostate size was 229.9 cc (range 175-535 cc) and 36 (65.5%) were in urinary retention. Mean preoperative prostate-specific antigen (PSA) was 8.58 ng/mL, American Urological Association Symptom Score (AUASS) 22.3, and Qmax 8.8 mL/second. At 3 months postoperative follow-up mean AUASS was 6.7, PSA 0.87 ng/mL and Qmax 20.4 mL/second. All comer same-day discharge rate was 70% (38/55). Of patients planned for same-day discharge 38/45 (84%) were effective. Average LOS for all patients was 11.8 hours with catheterization of 21.2 hours. When compared with 2010 published large gland outcomes, our current LOS represents a 220% reduction. Looking specifically at patients planned for same-day discharge, average LOS and catheter duration was 8.8 and 17.0 hours, whereas LOS and catheter duration for patients planned for admission was 25.7 and 39.4 hours, respectively. Conclusions: We report the first outcomes of preoperatively planned same-day discharge for HoLEP in large glands (≥175 cc). A combination of technologic advances and optimization of technique have allowed for a safe adoption of same-day discharge, providing additional advantages over alternative large gland treatments.

High-efficient heat flux manipulation of micro-scale thermal metamaterials with facile functional unit design

Based on the novel macro-thermophysical properties exhibited by its peculiarly artificially design structure, thermal metamaterials have been widely used in the harvest and management of thermal energy. Herein, a facile micro-scale thermal functional unit structure is proposed assisted by an advanced picosecond laser technology to realize the fabrication of thermal metamaterials with thermal shielding and thermal concentrating. To obtain the optimal design criterion of thermal functional units, the effects of thermal conductivity ratio, layer orientation angle, and laminated thickness on thermal conduction are investigated. Both simulation and experiment validate that thermal metamaterials assembled by diverse thermal functional units with different orientation angles exhibit completely neoteric performances of thermal concentrating and shielding. Besides, the results verify that the micro-scale thermal metamaterials exhibit better heat flux regulation capability and higher thermal concentration efficiency. Additionally, the effect of inevitable air convection on the thermal performance of these metamaterials has also been evaluated. This work provides an effective strategy to achieve small-scale thermal energy harvesting and protection by using thermal metamaterials with micro-structure.

The Role of the Laser Safety Officer and Laser Safety Programs in Clinical Practice.

Recent advancements in laser technology have led to its expanded utilization in smaller clinical settings and medical spas, particularly for facial rejuvenation and the treatment of other aesthetic concerns. Despite the increasing popularity of this technology, discussion of laser safety programs has remained limited, mostly to operating rooms at larger clinical institutions. Although smaller facilities do not operate at the same capacity as a large hospital or medical center, the requirements for utilizing a laser are no less stringent. Employers must comply with local and federal regulations, the Occupational Safety and Health Administration (OSHA) General Duty Clause, American National Standards Institute (ANSI) standards, and professional recommended practices applicable to their business. Although the laser safety officer (LSO) is often a full-time position within larger facilities, smaller clinical settings and medical spas may be limited in staff number. It is important, therefore, that clinical practices establish laser policies and procedures with consideration of their individual needs and capabilities. In this paper, we will define a laser safety program, highlight basic requirements needed to establish this program, and outline the specific responsibilities of the LSO. To ensure that safe laser practices are being conducted at the healthcare facility, it is imperative that small business owners are aware of these regulations and standards in place for the operation of laser systems.

Three-Photon Spectroscopy of Porphyrins.

Recent advances in laser technology have made three-photon (3P) microscopy a real possibility, raising interest in the phenomenon of 3P absorption (3PA). Understanding 3PA of organic chromophores is especially important in view of those imaging applications that rely on exogenous probes, whose optical properties can be manipulated and optimized. Here, we present measurements and theoretical analysis of the degenerate 3PA spectra of several phosphorescent metalloporphyrins, which are used in the construction of biological oxygen probes. The effective 3PA cross sections (σ(3)) of these porphyrins near 1700 nm, a new promising biological optical window, were found to be on the order of 1000 GM3 (1 GM3 = 10-83 cm6 s2), therefore being among the highest values reported to date for organic chromophores. To interpret our data, we developed a qualitative four-state model specific for porphyrins and used it in conjunction with quantitative analysis based on the time-dependent density functional theory (TDDFT)/a posteriori Tamm-Dancoff approximation (ATDA)/sum-over-states (SOS) formalism. The analysis revealed that B (Soret) state plays a key role in the enhancement of 3PA of porphyrins in the Q band region, while the low-lying two-photon (2P)-allowed gerade states interfere negatively and diminish the 3PA strength. This study features the first systematic examination of 3PA properties of porphyrins, suggesting ways to improve their performance and optimize them for imaging and other biomedical applications.

Numerical simulation of super-continuum laser propagation in turbulent atmosphere* *Project supported by the Director Fund of Advanced Laser Technology Laboratory of Anhui Province, China (Grant No. 20191002).

Considering the atmospheric extinction and turbulence effects, we investigate the propagation performances of super-continuum laser sources in atmospheric turbulence statistically by using the numerical simulation method, and the differences in propagation properties between the super-continuum (SC) laser and its pump laser are also analyzed. It is found that the propagation characteristics of super-continuum laser are almost similar to those of the pump laser. The degradation of source coherence degree may cause the relative beam spreading and scintillation indexes to decrease at different propagation distances or different turbulence strengths. The root-mean-square value of beam wandering is insensitive to the variation of source correlation length, and less aperture averaging occurs when the laser source becomes less coherent. Additionally, from the point of view of beam wandering, the SC laser has no advantage over the pump laser. Although the pump laser can bring about a bigger aperture average, the SC laser has a lower scintillation which may be due to the multiple wavelength homogenization effects on intensity fluctuations. This would be the most important virtue of the SC laser that can be utilized to improve the performance of laser engineering.

Lasers in Glaucoma: an Overview.

Lasers have been in use as a treatment modality of glaucoma for more than last four decades. Each passing year has added newer dimensions to the existing laser technologies enhancing their safety and efficacy profile. This has become possible due to continuous research and innovations with proper understanding of the mechanism of action of different variety of lasers as treatment options. Each category of glaucoma has different underlying pathologies. Adequate knowledge and understanding of indications, limitations and hazards of these laser procedures are must before their application for improvising outcome. Recent years have witnessed a revolution this field. A thorough literature search was conducted in PubMed, Medline, the Cochrane Library Database, EMBASE, and Scopus and Google Scholar until May 2020 using the keywords, and all the articles pertaining to the relevant topics were included in this review. Purpose of this review is to summarize the important laser procedures currently in use for managing glaucoma along with updating the readers with recent advances in laser technologies, their extended applications and also analyzing possible future implications.

Ba(MoO2F)2(XO3)2 (X = Se and Te): First Cases of Noncentrosymmetric Fluorinated Molybdenum Oxide Selenite/Tellurite Through Unary Substitution for Enlarging Band Gaps and Second Harmonic Generation.

Nonlinear optical (NLO) materials have critically important applications in advanced laser technologies. However, achieving a good balance between the mutual competing NLO properties and band gap within one molecular structure remains a great challenge. In this study, two alkaline earth metal fluorinated molybdenum oxide selenite/tellurite, Ba(MoO2F)2(XO3)2 [X = Se (BMFS) and Te (BMFT)], were synthesized through a facile unary substitution: BMFS was obtained by partial substitution of oxygen atoms with highly electronegative fluorine in the parent compound BaMo2O5(SeO3)2 (BMS), while BMFT was achieved by further replacing lone-pair Se4+ cations in BMFS with heavier Te4+ cations in the same main group. By partially replacing oxygen with fluorine, BMFS shows a broadened band gap and enhanced second harmonic generation (SHG) response compared to BMS owing to the high electronegativity of fluorine anions and the favorable orientation and alignment of NLO-active [MoO5F]5- and [SeO3]2- groups, which is relatively rare for unary anion substitution. BMFS and BMFT are isostructural and both belong to the polar space group Aba2, featuring a three-dimensional (3D) double-layered framework composed of 2D [MoO4F(XO3)]∞ anionic layers interconnected by divalent barium cations. Both BMFS and BMFT exhibit good optical performance, including large SHG responses (3× and 4× KH2PO4), wide band gaps (3.30 and 3.27 eV) and optical transparency window, and high laser damage thresholds (60× and 53× AgGaS2), demonstrating their potential applications as promising second-order NLO crystals. DFT calculations have elucidated the crucial role of the [MoO5F]5- groups in the enlarged band gaps and enhanced SHG responses in BMFS and BMFT. This work proposes a feasible unary substitution strategy for synthesizing the first polar fluorinated molybdenum oxide selenite/tellurite with synchronously enlarged band gaps and SHG efficiency.

Combining High‐Tech Glass Innovations with Advanced Laser Technologies

AbstractAs glass wafer products become more specialized and die sizes get smaller, the demand for high‐speed singulation of glass wafers is increasing. Corning Laser Technologies utilizes the advantages of precise laser dicing to process optimized glass types with adapted CTE values, high transmission, and specific refractive indices to enable existing and emerging applications.

Orbiting and In-Situ Lidars for Earth and Planetary Applications.

At NASA Goddard Space Flight Center, we have been developing spaceborne lidar instruments for space sciences. We have successfully flown several missions in the past based on mature diode pumped solid-state laser transmitters. In recent years, we have been developing advanced laser technologies for applications such as laser spectroscopy, laser communications, and interferometry. In this article, we will discuss recent experimental progress on these systems and instrument prototypes for ongoing development.

Maxwell Meets Marangoni—A Review of Theories on Laser‐Induced Periodic Surface Structures

AbstractSurface nanostructuring enables the manipulation of many essential surface properties. With the recent rapid advancements in laser technology, a contactless large‐area processing at rates of up to m2 s−1 becomes feasible that allows new industrial applications in medicine, optics, tribology, biology, etc. On the other hand, the last two decades enable extremely successful and intense research in the field of so‐called laser‐induced periodic surface structures (LIPSS, ripples). Different types of these structures featuring periods of hundreds of nanometers only—far beyond the optical diffraction limit—up to several micrometers are easily manufactured in a single‐step process and can be widely controlled by a proper choice of the laser processing conditions. From a theoretical point of view, however, a vivid and very controversial debate emerges, whether LIPSS originate from electromagnetic effects or are caused by matter reorganization. This article aims to close a gap in the available literature on LIPSS by reviewing the currently existent theories of LIPSS along with their numerical implementations and by providing a comparison and critical assessment of these approaches.

Safety Guidelines Concerning the Use of Protective Eyewear and Gauze During Laser Procedures.

The advancement of laser technology has seen its use gain popularity across a wide range of specialties to treat diseases, as well as address aesthetic concerns. In order to protect both the patient and the healthcare personnel providing treatment, instruction and knowledge of laser safety remain of utmost importance. In this paper, we discuss the classification of laser systems, review ocular injuries that may be caused by inappropriate laser exposure, and provide background on laser protective eyewear. In addition, we highlight the current recommendations for proper eyewear during laser use outlined in the American National Standards Institute standard Z136.3, Safe Use of Lasers in Health Care. Finally, although it is common in some healthcare facilities to place gauze under external eye shields or use gauze alone over eyes during laser procedures, this practice poses an extreme risk to both patients and healthcare personnel. Therefore, we discuss why the use of gauze under eyewear for any laser procedures is not recommended, and instead, offer suggestions to consider when acquiring safe and comfortable patient eyewear.

Tunable third harmonic generation in the vacuum ultraviolet region using dielectric nanomembranes

Tunable coherent light sources operating in the vacuum ultraviolet (VUV) region in the 100–200-nm (6–12 eV) wavelength range have important spectroscopic applications in many research fields, including time-resolved angle-resolved photoemission spectroscopy. Recent advances in laser technology have enabled the upconversion of visible femtosecond lasers to the vacuum and extreme ultraviolet regions. However, the complexity of their experimental setups and the scarcity of bulk nonlinear crystals for VUV generation have hampered its widespread use. Here, we propose the use of a free-standing dielectric nanomembrane as a simple and practical method for tunable VUV generation. We demonstrate that third harmonic VUV light is generated with sufficient intensity for spectroscopic applications from commercially available SiO2 nanomembranes of submicron thicknesses under excitation with visible femtosecond laser pulses. The submicron thickness of the nanomembranes is optimal for maximizing VUV generation efficiency and prevents self-phase modulation and spectral broadening of the fundamental beam. The observed VUV photons are up to 107 photons per pulse at 157 nm with a 1-kHz repetition rate, corresponding to a conversion efficiency of 10−6. Moreover, the central VUV wavelength can be tuned in the 146–190-nm wavelength range by changing the fundamental wavelength. We also explore material and thickness dependence with experiments and calculations. The presented results suggest that dielectric nanomembranes can be used as practical nonlinear media for VUV spectroscopic applications.

Investigation of the differences between photochemical and photothermal laser ablation on the shear strength of CFRP/CFRP adhesive joints

Ensure high bonding strength and durability is very important for composite materials that are widely used by many different industries. In order to achieve this, the surfaces of the composite materials should be prepared for the adhesion process. Surface preparation with laser is a promising technique for the adhesive joint. However, the diversity offered by the advances in laser technologies and the multiplicity of parameters that must be controlled in laser material processing makes the process somewhat complex. In the present study, two different lasers have been used with different wavelengths (355 nm (UV) and 10600 nm (IR)) and pulse durations (4,4 ns and 5 μs), to increase the lap shear strength of the adhesive joint of carbon fiber reinforced polymer (CFRP) materials. While the ultraviolet (UV) laser with high photon energy creates photo-chemical ablation, infrared laser (IR) causes photo-thermal ablation due to their low photon energy. CFRP samples treated with different lasers and the accumulated laser fluences have been adhesively joined and the results evaluated experimentally. According to the results, differences in laser ablation mechanism cause structural differences on CFRP surfaces. While resolidified epoxy was observed on CO2 laser treated surfaces, no residues were detected on UV laser treated surfaces. However, to avoid delamination or fiber damage risks an optimization of laser parameters are recommended to be performed for both laser systems.

Universal crossed beam imaging studies of polyatomic reaction dynamics.

The marriage between high level quantum calculations and experimental advances in laser technology, quantum state control, and detection techniques have opened the door to the study of molecular collision dynamics at a new level of detail. However, one current challenge lies in adapting these powerful strategies to address questions beyond the scope of the small ground state systems that have largely been the focus of reaction dynamics investigations to-date. For molecules with intermediate or large size (more than 6 atoms), lack of spectroscopic information and spectral congestion limit quantum state preparation, control and detection for experiment, and the large number of degrees of freedom of the system makes accurate quantum dynamics calculations prohibitively expensive. Nevertheless, studies of the chemical dynamics of such systems can reveal novel aspects of reactivity not anticipated based upon the behavior of smaller model systems. This Perspective will highlight applications of soft vacuum ultraviolet photoionization at 157 nm as a universal probe in combination with crossed beams and DC slice velocity map ion imaging to study bimolecular reaction dynamics of molecules of intermediate or large size, illuminated with support of high-level ab initio calculations. Here, we report on the chemical dynamics of atomic oxygen or chlorine reactions with organic compounds: propanol isomers, alkylamines (N(CH3)3 and NH(CH3)2), and isobutene ((CH3)2CCH2) studied using this approach. The polyatomic radical products from the hydrogen abstraction process have been detected by 157 nm photoionization and their slice ion images embody translational energy and angular information that directly reflect the underlying collision dynamics. Various reaction mechanisms (such as direct abstraction and addition-elimination) along with the involvement of roaming dynamics and novel intersystem crossing pathways are presented. These demonstrate the power of this technique to reveal fundamentally new aspects of reaction dynamics that arise in larger reaction systems.

Research on Laser Fusion and its Applications

In the last half century, laser fusion research has been intensively pursued to achieve energy production. The fuel for laser fusion, deuterium, can be abundantly found in sea water. Compared to fission scheme, fusion is much more benign to our environment. Along with the remarkable progress of laser technology, the laser fusion research has reached a crucial phase, and many applications in terms of such advanced laser technology are now under quick development in different fields such as medical treatment, energy, and industry.