Single Beam Method Research Articles

Morphological changes analysis using 3D bathymetric surveys in Chilia Branch - Bystroe Channel bifurcation area

The Bystroe Channel project with transboundary environmental impact in the Danube Delta, area of great ecological significance that has already a strong anthropic footprint, requires close monitoring of water quality parameters in order to determine their tendencies and their impact on the ecosystem components. Riverbed bathymetry surveys using multibeam echo-sounders are of high interest due to the data resolution and coverage capabilities that surpass the single-beam methods. Two riverbed elevation datasets, recorded in consecutive years, have been used to carry out morphological comparative analysis for the area where Chilia branch bifurcates in Bystroe Channel and Old Stambul. The analysis has been performed both on the bathymetry grids as a whole and on 3 longitudinal and 9 transversal river sections, the morphological changes values being in majority included in [-0.5 m;+0.5 m], with a minimum of -2.4 m and a maximum of 2.2 m, showing the bifurcation influence on the erosion/deposition processes results.

Single-beam technique for ultrashort pulse characterization based on the nonlinear ellipse rotation signal

We present a single-beam method based on the third-order nonlinear-ellipse-rotation (NER) measurement in thick samples to determine the pulse properties, including the duration and linear chirp. Our approach exploits the influence of the intrinsic second-order dispersions of the nonlinear materials, which affect the NER signal as a function of propagation. Two advantages can be highlighted: no delay line is required, and there are no phase-matching issues. To test our method, we characterized ultrafast chirped pulses from a Ti:sapphire amplified laser system and tunable pulses from an optical parametric amplifier using two samples with high dispersions and nonlinearities: SF6 and LaSF-N30 optical glasses.

Advanced micro- & nanostructuring for enhanced biocompatibility of stainless steel by multi-beam and beamshaping technology

Biocompatibility is one of the key issues for implants, especially in the case of stainless steel with medium to low biocompatibility, which may lead to a lack of osseointegration and consequently to implant failure or rejection. To precisely control preferential cell growth sites and, consequently, the biocompatibility of prosthetic devices, two types of surfaces were analyzed, containing periodic nanogrooves laser induced periodic surface structure (LIPSS) and square-shaped micropillars. For the fast and efficient production of these surfaces, the unique combination of high energy ultrashort pulsed laser system with multi-beam and beamshaping technology was applied, resulting in increased productivity by 526% for micropillars and 14 570% for LIPSS compared to single beam methods. In vitro analysis revealed that micro and nanostructured surfaces provide a better environment for cell attachment and proliferation compared to untreated ones, showing an increase of up to 496% in the number of cells compared to the reference. Moreover, the combination of LIPSS and micropillars resulted in a precise cell orientation along the periodic microgroove pattern. The combination of these results demonstrates the possibility of mass production of functionalized implants with control over cell organization and growth. Thus, reducing the risk of implant failure due to low biocompatibility.

Wavelength-Independent Correlation Detection of Aberrations Based on a Single Spatial Light Modulator

The cumulative achievements in the fields of science and technology have allowed us to substantially approach the solution of the phase problem in optics. Among all phasometric methods, single-beam methods are the most promising, since they are more variable and versatile. Single-beam methods are based either on the analysis of the intensity distribution, as is conducted by interferometers and wavefront sensors, or on the transformation of the phase into an intensity distribution due to spatial filtering, as is conducted by holographic methods. However, all these methods have the problem of working with polychromatic radiation and require spectral filters to process such radiation. This paper presents a new approach to the synthesis of Fourier holograms used in holographic wavefront sensors that make it possible to create achromatic elements and work with white light without the use of additional filters. The approach was numerically and experimentally verified.

Dual-Beam Circular Dichroism Spectroscopy of Jet-Cooled Chiral Molecules

Circular dichroism (CD) spectroscopy of jet-cooled molecules provides conformation-specific CD spectra. However, its widespread utilization has been limited by the weak CD effects and the low density of gas-phase molecules. Here, we developed a dual-beam method to improve the sensitivity and accuracy of gas-phase CD measurements. Circularly and linearly polarized pulses were generated from a single laser pulse and used to irradiate a single molecular-beam pulse to produce two ion peaks. The ion peaks induced by linearly polarized pulses were subtracted from those induced by circularly polarized pulses to correct the CD values for the pulse-to-pulse fluctuations in laser power and gas density. The resonant two-photon ionization CD spectrum of (1R,2R)-(-)-pseudoephedrine revealed that the standard deviations of CD values measured using the dual-beam method were three times lower than those measured using a single-beam method. The dual-beam method provides an effective, accurate, and easy-to-use tool to obtain gas-phase CD spectra.

Additive manufacturing of NdFeB magnets by synchronized three-beam laser powder bed fusion

Neodymium iron boron (NdFeB) magnet that is manufactured using laser powder bed fusion (LPBF) machines has attracted attention since the complex magnetic parts can be directly manufactured. This study used LPBF systems with single and three-beam lasers to fabricate NdFeB components, and the effects of different process parameters (pulsed or continuous wave laser, powder layer thickness, laser power, and scanning velocity) on the magnetic characteristics were investigated. The results from the synchronized three-beam method using the two-zone scanning strategy improved the maximum magnetic energy product by 33.42 kJ/m3, and the processing time was decreased by 38% compared to the single-beam method.

Adhesion strength of die attach film for thin electronic package at elevated temperature

Adhesion strength of a thin film for electronic packaging was investigated. The effects of temperature and loading rate on the adhesion were observed considering the viscoelasticity of adhesive. Various temperature conditions over the glass transition temperature of the adhesive were applied with controlled loading rates. A small hot plate was specially designed to control the temperature. Loading rate was controlled by a servo motor. A cantilever specimen was fabricated by two rectangular silicon chips. The adhesion was measured by a modified single cantilever beam method. Bending force was applied to the cantilever using rotatable jig. Adhesion strength was found to strongly depend on the temperature and loading rate. Below the glass transition temperature (Tg), the adhesion strength was increased with increasing loading rate. Near the Tg, the adhesion strength was decreased with increasing loading rate. Above the Tg, the adhesion strength did not significantly depend on the loading rate.

Laser Tweezers Raman Microspectroscopy of Single Cells and Biological Particles.

Laser tweezers Raman spectroscopy (LTRS) is a variation of micro-Raman spectroscopy that is used to analyze single cells and biological particles suspended in an aqueous environment. The Raman spectrum of the cell/particle reflects its intrinsic biochemical composition and molecular structures. The technique utilizes a laser trap generated by a tightly focused Gaussian laser beam to physically manipulate individual cells and immobilize them in the laser focal volume. The same laser that is used for optical trapping also simultaneously excites Raman signals from the trapped cell, which are detected using a spectrometer and a confocal detection setup. LTRS offers unique capabilities not commonly found in other optical cytometry methods, such as label-free chemical analysis, multi-parametric chemical detection with a single excitation laser, and a non-photobleaching signal that can be used to quantitate and monitor dynamic chemical changes. This chapter provides guidelines on the design of a single beam LTRS microscope and methods for building and aligning the system. Operating procedures for trapping particles and acquiring spectra and a summary of data analysis techniques are provided.

Single-beam phase-modulated stimulated Raman scattering microscopy with spectrally focused detection

We present a single-beam coherent Raman microscopy method based on pump–probe, time-resolved stimulated Raman scattering (SRS) measurements with shaped probe pulses. In the single-beam method, we divide a broadband laser spectrum into three frequency bands for the pump, phase-modulated (PM) probe, and local oscillator (LO) probe pulses. Multiple low-wavenumber Raman modes are efficiently excited by an impulsive pump pulse, and a specific Raman mode can be selectively probed using temporal beam coupling between the PM and LO probe pulses via the Raman-induced refractive index modulation. To achieve both high sensitivity and a high spectral resolution, we allocate a large spectral bandwidth (164 cm−1) to two probe bands and use a new selective detection scheme based on the spectral focusing technique. By giving a strong group delay dispersion to the probes (45000 fs2), we can obtain an improved spectral resolution of down to 25 cm−1. In a proof-of-concept experiment, the intrinsic molecular-vibration contrast of sevoflurane, an inhaled anesthetic drug, is successfully visualized. This result suggests that single-beam SRS imaging with pulse shaping is a potentially powerful tool for detecting the Raman signals of small-molecule drugs in living cells and tissues.

Verification of the performance of rotatable jig for a single cantilever beam method using the finite element analysis

The performance of new jig for single cantilever beam test method was verified by finite element analysis. Two types of jig were designed for a small specimen that had relatively short length compared to the width of cantilever; one was simple fixed jig and the other was specially designed rotatable jig. The rotatable jig has a rotatable seesaw which adjusts the experimental misalignments between the specimen and test machine. Among the three translational and three rotational misalignments, following three important factors were considered; rotation about x-axis, rotation about z-axis, and translation in y-axis. Adhesive layer was modeled by cohesive zone element, and crack propagation behavior and the deviation of energy release rate were investigated. The fixed jig showed undesired asymmetric crack propagation and large deviation of energy release rate when it had rotational misalignment about x-axis. However, the proposed new rotatable jig showed almost symmetrical crack propagation and small deviation of energy release rate regardless of misalignments. Rotational motion of the seesaw automatically compensated the rotational misalignment of the specimen. The rotatable jig also showed relatively small deviation of energy release rate compared with the fixed jig by the rotational misalignment about the z-axis. In contrast, the rotatable jig showed deviation of energy release rate by translational misalignments in the y-axis. However, the magnitude of the deviation was very small within the controllable range of experimental misalignment. In conclusion, it was found out that the proposed jig was appropriate for the measurement of adhesion of a small specimen by single cantilever beam method.

Periodic Surface Structures Induced by a Single Laser Beam Irradiation

Methods for inscribing periodic surface patterns by light, especially those characterized by the ability to control the pattern dimensions, are continuously sought for. In this paper, a periodic pattern, which is called the willow structure, is written to a supramolecular polymer-azobenzene complex using a single coherent laser beam of linear polarization. The willow structure can be an alternative to the commonly used surface relief grating written with an interference pattern once it is known how to manipulate its period. It is shown that the periodicity of the structure obtained with the one-beam approach can be controlled by changing the thickness of the polymer layer and the inscription temperature, in addition to the wavelength of the inscribing light. This information is useful for the utilization of the single-beam method as a way for obtaining periodic structures with desired dimensions.

Correlation of the indentation fracture resistance measured using high-resolution optics and the fracture toughness obtained by the single edge-notched beam (SEPB) method for typical structural ceramics with various microstructures

The standardized SEPB method and an accurate IF technique recently developed by the authors were employed in order to clarify the correlation of KIC and KIFR for ceramics with various microstructures. Both KIFR calculated using Miyoshi׳s equation and Niihara’s equation were roughly proportional to KIC but the correlation was incomplete. KIFR calculated using Miyoshi׳s equation has a tendency to exhibit slightly smaller values than their KIC. In contrast, the relation between KIFR and KIC was reversed when Niihara׳s equation was used for the calculation of KIFR.

Development of single cantilever beam method to measure the adhesion of thin film adhesive on silicon chip

A method to measure the tensile adhesion of thin films on a silicon chip was developed. A new test machine was designed to obtain tensile adhesion by applying a single cantilever beam method. Self-alignment of the specimen was accomplished by a specially designed jig and mount. The specimen was designed to allow fabrication by using a commercial manufacturing process. The developed method was applied to measure the adhesion of die attach films having various thicknesses ranging from 5μm to 20μm. Adhesion between the film adhesive and the top surface of a silicon chip was successfully measured. It was shown that the measured adhesion was independent of crack length and robust against variation of the initial alignment of specimen.

Dual-beam wavelength modulation spectroscopy for sensitive detection of water vapor

A technique was reported for sensitive detection of water vapor based on dual-beam wavelength modulation spectroscopy (WMS). Particular attention was focused on the problem of laser power variation (LPV) and residual amplitude modulation (RAM), which accounted for the absorption profile’s distortion during application of WMS. Impact from LPV and RAM was eliminated by photocurrent normalization through a balanced ratiometric detector, which was a dual-beam technique with shot noise-level performance. When consideration of distortion was required, this could enormously simplify the spectra analysis procedure. In the experiment symmetry of the WMS, profile had gotten an improvement by a factor of about 102 compared with traditional single-beam method. During the application test of water vapor detection, the detected amplitude of WMS was well proportional to water vapor concentration ranging from 25 to 1,048 ppmv and the sensitivity was achieved to be 52 ppbv for just a 10-cm optical path length.

Single beam optical vortex tweezers with tunable orbital angular momentum

We propose a single beam method for generating optical vortices with tunable optical angular momentum without altering the intensity distribution. With the initial polarization state varying from linear to circular, we gradually control the torque transferred to the trapped non-absorbing and non-birefringent silica beads. The continuous transition from the maximum rotation speed to zero without changing the trapping potential gives a way to study the complex tribological interactions.

Noise statistics of phase-resolved optical coherence tomography imaging: single-and dual-beam-scan Doppler optical coherence tomography

Noise statistics of phase-resolved optical coherence tomography (OCT) imaging are complicated and involve noises of OCT, correlation of signals, and speckles. In this paper, the statistical properties of phase shift between two OCT signals that contain additive random noises and speckle noises are presented. Experimental results obtained with a scattering tissue phantom are in good agreement with theoretical predictions. The performances of the dual-beam method and conventional single-beam method are compared. As expected, phase shift noise in the case of the dual-beam-scan method is less than that for the single-beam method when the transversal sampling step is large.

Fracture Toughness Properties of Gd123 Superconducting Bulks

Abstract Fracture toughness properties of melt growth GdBa 2 Cu 3 Ox (Gd123) large single domain superconducting bulks with Ag 2 O of 10 wt% and Pt of 0.5 wt%; 45 mm in diameter and 25 mm in thickness with low void density were evaluated at 77 K through flexural tests of specimens cut from the bulks, and compared to those of a conventional Gd123 with voids. The densified Gd123 bulks were prepared with a seeding and temperature gradient method; first melt processed in oxygen, then crystal growth in air; two-step regulated atmosphere heat treatment. The plane strain fracture toughness, K IC was obtained by the three point flexure test of the specimens with through precrack, referring to the single edge pre-cracked beam (SEPB) method, according to the JIS-R-1607, Testing Methods for Fracture Toughness of High Performance Ceramics. The results show that the fracture toughness of the densified Gd123 bulk with low void density was higher than that of the standard Gd123 bulk with voids, as well as the flexural strength previously reported. We also compared the fracture toughness of as-grown bulks with that of annealed bulks. The relation between the microstructure and the fracture toughness of the Gd123 bulk was clearly shown.

Sensitive and robust second-harmonic interferometer for measuring the dispersion of the electro-optic coefficients in bulk materials

Second-harmonic interferometry (SHI) is proposed for measuring the electro-optic (EO) coefficients of massive media. It combines the advantages of interferometric techniques with the mechanical stability of single-beam methods, simultaneously skimming the wavelength dispersion of the EO response. For demonstrating the effectiveness of the SHI technique, the EO coefficients r(33)(T) and r(13)(T) of the EO crystal lithium niobate are measured simultaneously at 1064 and 532 nm.

Polarization dependence of two‐photon absorption coefficient and nonlinear susceptibility tensor in InP

AbstractTwo‐photon absorption (TPA) effect in (001) InP is investigated using fs laser. Its dependences on wavelength and polarization are clarified by single and double beam methods with linearly polarized lights. Characteristic features are revealed and discussed with scaling law, crystal bonding and mutual relation of polarizations for double beams. The results are successfully analyzed on the basis of the third‐order susceptibility tensor for comprehensive understanding of TPA effect at any polarization geometry. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Z–Scan Investigations on Organic and Semiorganic Single Crystals for Optical Device Applications

Modern development of optical devices calls for new nonlinear optical (NLO) materials with extraordinary properties. Organic and semi-organic materials are getting considerable attention because of their potential uses in various optical telecommunication devices including optical modulation, optical switching and optical limiters. The Z-scan technique is a simple and sensitive single beam method to determine both the nonlinear refractive index and nonlinear absorption coefficient of materials. In this investigation Z scan was performed on potassium acid phthalate (KHP) and methyl p-hydroxybenzoate (p-MHB) single crystals by using Nd: YAG laser at 532 nm. The results were analyzed and compared. The outcome of this investigation could help us to learn the material completely and also to understand the relations between molecular structure, linear absorption and optical nonlinearity the crystals. The entire outcome of this work suggests that KHP and p-MHB are potential materials for optical device application.