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The purpose of this paper is to analyse nanosecond pulsed laser ablation on both metallic materials and non-metallic materials; a comparison between metallic materials and non-metallic materials has also been included.

In this paper, FEM method has been used to calculate the result by means of the finite element method. Furthermore, all the analyses are based on thermal theories.

The paper presents a comparison of metallic and non-metallic materials. Besides, the effect of how laser parameter changes would influence the ablation depth has also been assessed.

All studies in this paper are based on classical thermal theories. Thermal theories are not applicable some times.

With the results of this paper, suggestions are made so that experiments and manufactures could be optimised and improved.

The purpose of this paper is to present a numerical analysis of the laser surgery of port wine stain (PWS) with cryogen spray cooling to compare the treatment effect between pulse dye laser and Nd:YAG laser, explain the incomplete clear of the lesion and optimize the laser parameter.

The complex structure of skin and PWS is simplified to a multi-layer skin model that consists of top epidermal layer and underneath dermis layer embedded with discrete blood vessels. The cooling effect of cryogen spray before laser firing is quantified by a general correlation obtained recently from the experimental data. The light distribution is modeled by the Monte Carlo method. The heat transfer in skin tissue is calculated by Pennes bioheat transfer model. The thermal damage of blood vessel is quantified by the Arrhenius damage integral.

For the vessel size studied (10-120 µm), pulse duration is recommended shorter than 6 ms. Large and deeply buried vessels, which may survive from 595 nm laser irradiation, can be coagulated by 1,064 nm laser due to its deep light penetration depth in skin. Furthermore, a desired uniform heating within the large vessel lumen can be achieved by 1,064 nm laser whereas 595 nm laser produce non-uniform heating.

The possible reason for the poor responding and incomplete clearance lesions is clarified. Laser wavelength and pulse duration are suggested to improve the clinical results.

The advantages of lasers over broad‐band light sources for spectroscopic measurements have long been recognized. Laser techniques offer the ability to measure the concentrations of trace species in a gas stream in “real time” with sensitivity and molecular selectivity not possible with broad band spectroscopic techniques. Until recently, the use of laser‐based instruments has been largely limited to laboratory or one‐of‐a‐kind devices. However, the increased availability of solid‐state tunable diode lasers, recent advancements in fiber optic coupling and advanced signal processing have made it possible to develop instruments that offer customers enabling technology at an affordable price. Spectrum Diagnostix has developed a family of tunable diode laser‐based instruments used in a variety of applications including: fugitive release detection of HF and H₂S in the refining and petrochemical industries, stack monitoring, and using extractive sample probe, in situ process control. SpectraScan instruments obtain their high sensitivity and chemical selectivity utilizing a technique known as wavelength modulated spectroscopy. Described simply, a near infra‐red diode laser’s wavelength is scanned rapidly and repeatedly through a molecular absorption line. A photodetector senses the instantaneous fraction of emitted laser power that is transmitted through the chemical bearing gas. Measurement of the relative amplitudes of offline to online transmission yields a precise value of the quantity of chemical along the laser beam’s path. The amplitude modulated signals are then detected using established radio receiver and signal processing techniques. The SpectraScan monitors are designed for permanent installation in harsh industrial and petrochemical environments and are approved for Class I, Division 2 hazardous area use. Describes the SpectraScan instruments, their field applications, and reviews operating data compiled from open path measurements of HF in refineries.

The normal spectral absorptance of a number of metal, ceramic and polymer powders susceptible to be utilised for selective laser sintering (SLS) technique was experimentally determined. The measurements were performed with two laser wavelengths of 1.06μm and 10.6μm obtained by using two lasers – Nd‐YAG and CO₂ respectively. The change in the powder absorptance with time during laser processing was also investigated. The effect of the absorptance characteristics on the sintering process is discussed.

An interferogram is produced by modulating the difference between the extraordinary refractive index and the ordinary refractive index for photoelastic crystals in photoelastic-modulated Fourier transform spectrometers (PEM-FTs). Due to the influence of the refractive index dispersion characteristics on the maximum optical path difference of the interferogram, it is necessary to study wavelength calibration methods.

A wavelength calibration method for PEM-FTs was proposed based on the modulation principle of the photoelastic-modulated interferometer and the relationship between the maximum optical path difference and the refractive index difference. A 632.8 nm narrow-pulse laser was used as a reference source to measure the maximum optical path difference () of the interferogram, and the parameter was used to calculate the discrete frequency points in the frequency domain. To account for the influence of refractive index dispersion on the maximum optical path difference, the refractive index curve for the photoelastic crystal was used to adjust the discrete frequency coordinates.

The error in the reconstructed spectral frequency coordinates clearly decreased. The maximum relative error was 2.5%. A good solar absorption spectrum was obtained with a PEM-FT experimental platform and the wavelength calibration method.

The interferogram is produced by adjusting the difference between extraordinary refractive index and ordinary refractive index for the photoelastic crystal in the PEM-FTs. Given the wavelength dependence on the refractive indices, in view of the modulation principle of the photoelastic modulated interferometer, the relationship between the maximum optical path difference and the refractive index difference, the variation law of the refractive index of the photoelastic crystal and the process of spectral reconstruction is presented in this paper.

Optoelectronic components such as lasers and avalanche photodiodes have already revolutionised long distance transmission, and yet the technology is still in its infancy. Future generations of optoelectronic components will see the increasing integration of electronic, optoelectronic and optical functions on single chips, bringing about dramatic improvements in performance and the lower costs that will be required for widescale introduction of broadband networks and services.

The purpose of this study is, to compare laser-based additive manufacturing and subtractive methods. Laser-based manufacturing is a widely used, noncontact, advanced manufacturing technique, which can be applied to a very wide range of materials, with particular emphasis on metals. In this paper, the governing principles of both laser-based subtractive of metals (LB-SM) and laser-based powder bed fusion (LB-PBF) of metallic materials are discussed and evaluated in terms of performance and capabilities. Using the principles of both laser-based methods, some new potential hybrid additive manufacturing options are discussed.

Production characteristics, such as surface quality, dimensional accuracy, material range, mechanical properties and applications, are reviewed and discussed. The process parameters for both LB-PBF and LB-SM were identified, and different factors that caused defects in both processes are explored. Advantages, disadvantages and limitations are explained and analyzed to shed light on the process selection for both additive and subtractive processes.

The performance of subtractive and additive processes is highly related to the material properties, such as diffusivity, reflectivity, thermal conductivity as well as laser parameters. LB-PBF has more influential factors affecting the quality of produced parts and is a more complex process. Both LB-SM and LB-PBF are flexible manufacturing methods that can be applied to a wide range of materials; however, they both suffer from low energy efficiency and production rate. These may be useful when producing highly innovative parts detailed, hollow products, such as medical implants.

This paper reviews the literature for both LB-PBF and LB-SM; nevertheless, the main contributions of this paper are twofold. To the best of the authors’ knowledge, this paper is one of the first to discuss the effect of the production process (both additive and subtractive) on the quality of the produced components. Also, some options for the hybrid capability of both LB-PBF and LB-SM are suggested to produce complex components with the desired macro- and microscale features.

This paper focuses on some of the presentations given at a technical workshop on “Laser processing of polymer‐based materials”, organised by Association of Industrial Laser Users. Applications in cutting and welding are discussed and specifically how different combinations of polymer materials and laser types produce different results. Applications are described that include pre‐weakening of car trims for integrated airbags and “on the fly” scribing of web materials used in packaging. In several of these applications, robots play an important role in manipulating the laser beam.

The latest developments in the use of lasers for welding plastics are reviewed. Lasers were demonstrated as being suitable for welding plastics in 1970. However, it is only now that they are finding wide application following technical developments in transmission laser welding and ClearWeld™, and the availability of small, economic diode laser systems.

This paper aims to provide a sensor for fast, sensitive and selective ethylene (C₂H₄) concentration measurements.

The paper developed a sensor platform based on tunable laser absorption spectroscopy with a 3,266-nm interband cascade laser (ICL) as an optical source and a hollow waveguide (HWG) as a gas cell. The ICL wavelength was scanned across a C₂H₄ strong fundamental absorption band, and an interference-free C₂H₄ absorption line located at 3,060.76 cm⁻¹ was selected. Wavelength modulation spectroscopy with the second harmonic detection (WMS-2f) technique was used to improve the sensitivity. Furthermore, the HWG gas cell can achieve a long optical path in a very small volume to improve the time response.

The results show excellent linearity of the measured 2f signal and the C₂H₄ concentration with a correlation coefficient of 0.9997. Also, the response time is as short as about 10 s. The Allan variance analysis indicates that the detection limit can achieve 53 ppb with an integration time of 24 s.

The ethylene sensor has many meaningful applications in environmental monitoring, industrial production, national security and the biomedicine field.

The paper provides a novel sensor architecture which can be a versatile sensor platform for fast and sensitive trace-gas detection in the mid-infrared region.