scholarly journals Rainbow Archimedean spiral emission from optical fibres

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
F. Mangini ◽  
M. Ferraro ◽  
M. Zitelli ◽  
V. Kalashnikov ◽  
A. Niang ◽  
...  
Keyword(s):  
Laser Beam ◽  
Optical Tweezers ◽  
Laser Power ◽  
Near Infrared ◽  
Laser Source ◽  
Optical Fibres ◽  
Far Field ◽  
Archimedean Spiral ◽  
Spiral Shape ◽  
Helical Beam

AbstractWe demonstrate a new practical approach for generating multicolour spiral-shaped beams. It makes use of a standard silica optical fibre, combined with a tilted input laser beam. The resulting breaking of the fibre axial symmetry leads to the propagation of a helical beam. The associated output far-field has a spiral shape, independently of the input laser power value. Whereas, with a high-power near-infrared femtosecond laser, a visible supercontinuum spiral emission is generated. With appropriate control of the input laser coupling conditions, the colours of the spiral spatially self-organize in a rainbow distribution. Our method is independent of the laser source wavelength and polarization. Therefore, standard optical fibres may be used for generating spiral beams in many applications, ranging from communications to optical tweezers and quantum optics.

Approach to diameter measurement of optical fibres: Forward near-axis far-field interference

2001 ◽  
Vol 215 (4) ◽  
pp. 385-388 ◽  
Author(s):  
J Wu
Keyword(s):  
Laser Beam ◽  
Interference Pattern ◽  
Optical Fibre ◽  
Optical Fibres ◽  
Far Field ◽  
Diameter Measurement ◽  
Non Destructive

A new, simple, fast, accurate and non-destructive method is presented for determining the diameter of optical fibres. The technique is based on the analysis of the forward near-axis far-field interference pattern from an optical fibre illuminated by a laser beam perpendicular to its axis.

scholarly journals Residual stress reduction of LPBF-processed CM247LC samples via multi laser beam strategies

2021 ◽  
Author(s):  
Marcel Gerstgrasser ◽  
Michael Cloots ◽  
Josef Stirnimann ◽  
Konrad Wegener
Keyword(s):  
Residual Stress ◽  
Laser Beam ◽  
Stress Reduction ◽  
Laser Power ◽  
Electron Backscatter Diffraction ◽  
Laser Source ◽  
Scan Speed ◽  
Lateral Offset ◽  
Solidification Cracks ◽  
Backscatter Diffraction

AbstractBased on SLM parameters from previous works, which guarantee fully dense and crack free CM247LC samples, multi laser beam strategies have been pursued to reduce residual stresses or rather distortion during LPBF processing. By using a second post heating and non-melting laser source with a defocused laser beam and lateral offset, cantilever distortion is reduced more than 7.5%, compared to the reference. Based on pre-tests with 9 different offset parameters, the optimum offset has been identified. Also, an upper limit for the laser power of 65 W is identified for the second heat laser beam with a spot diameter of 380 μm, to avoid re-melting and creating new defects. A theoretical “two bar model,” to explain the residual stress behavior and reduction with multi laser beam offset strategy during the LPBF process, is presented. Furthermore, re-melting cracks, defects, and microstructure are analyzed in conjunction with the second defocused offset laser, in case of a 200 W laser power, an increased scan speed of 1300 mms/s, and a reduced hatch distance. Secondary electron signal (SE) images of re-melting cracks are analyzed and compared to SE-image of hot cracks (solidification cracks). Based on electron backscatter diffraction (EBSD), the results of the microstructure from the last mentioned multi laser beam approach, which creates re-melting cracks, are presented and analyzed.

A model of Gaussian laser beam self-trapping in optical tweezers for nonlinear particles

2021 ◽  
Vol 53 (8) ◽  
Author(s):  
Quy Ho Quang ◽  
Thanh Thai Doan ◽  
Kien Bui Xuan ◽  
Thang Nguyen Manh
Keyword(s):  
Laser Beam ◽  
Optical Tweezers ◽  
Gaussian Laser Beam ◽  
Self Trapping

scholarly journals Laser Superficial Fusion of Gold Nanoparticles with PEEK Polymer for Cardiovascular Application

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 971
Author(s):  
Oktawian Bialas ◽  
Mateusz Lis ◽  
Anna Woźniak ◽  
Marcin Adamiak
Keyword(s):  
Particle Size ◽  
Laser Beam ◽  
Gold Particle ◽  
Laser Power ◽  
Biomedical Application ◽  
Parameters Optimization ◽  
Size Reduction ◽  
Particle Size Reduction ◽  
Nano Gold ◽  
Gold Particle Size

This paper analyses the possibility of obtaining surface-infused nano gold particles with the polyether ether ketone (PEEK) using picosecond laser treatment. To fuse particles into polymer, the raw surface of PEEK was sputtered with 99.99% Au and micromachined by an A-355 laser device for gold particle size reduction. Biomimetic pattern and parameters optimization were key properties of the design for biomedical application. The structures were investigated by employing surface topography in the presence of micron and sub-micron features. The energy of the laser beam stating the presence of polymer bond thermalisation with remelting due to high temperature was also taken into the account. The process was suited to avoid intensive surface modification that could compromise the mechanical properties of fragile cardiovascular devices. The initial material analysis was conducted by power–depth dependence using confocal microscopy. The evaluation of gold particle size reduction was performed with scanning electron microscopy (SEM), secondary electron (SE) and quadrant backscatter electron detector (QBSD) and energy dispersive spectroscopy (EDS) analysis. The visibility of the constituted coating was checked by a commercial grade X-ray that is commonly used in hospitals. Attempts to reduce deposited gold coating to the size of Au nanoparticles (Au NPs) and to fuse them into the groove using a laser beam have been successfully completed. The relationship between the laser power and the characteristics of the particles remaining in the laser irradiation area has been established. A significant increase in quantity was achieved using laser power with a minimum power of 15 mW. The obtained results allowed for the continuation of the pilot study for augmented research and material properties analysis.

scholarly journals Laser beam calibration for wood surface colour treatment

2021 ◽  
Author(s):  
M. Jurek ◽  
R. Wagnerová
Keyword(s):  
Laser Beam ◽  
Power Control ◽  
Wood Surface ◽  
Laser Power ◽  
Production Quality ◽  
Chemical Processes ◽  
Continuous Control ◽  
Calibration System ◽  
Laser Engraving ◽  
Wood Surfaces

AbstractLaser engraving of photographs on wood surfaces is a challenging task. To optimize the outcome and production quality it is necessary to control every aspect of the laser engraving process. Most of the production machines and technologies overall are mainly focused on laser power control. However, with other systems and deeper knowledge of the wood characteristics it is possible to achieve even better quality. This paper deals with enlarging the number of achievable shades of burned wood and its optimization. A calibration system was developed to control colour shades of engraved wood with a combination of laser power and optic focus. With this approach it is possible to widen achievable palette of engraved shades by continuous control of chemical processes of laser and wood interaction. The production is divided into wood burning and wood carbonization by variation of laser beam focus.

Near-infrared-ray computed tomography with an 808 nm laser beam and high spatial resolutions

2021 ◽  
Vol 92 (1) ◽  
pp. 013702
Author(s):  
Eiichi Sato ◽  
Yasuyuki Oda ◽  
Sohei Yoshida ◽  
Kunihiro Yoshioka ◽  
Hodaka Moriyama ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Laser Beam ◽  
Near Infrared ◽  
Near Infrared Ray

scholarly journals Photoelectronic Properties of End-bonded InAsSb Nanowire Array Detector under Weak Light

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Xiaomei Yao ◽  
Xutao Zhang ◽  
Tingting Kang ◽  
Zhiyong Song ◽  
Qiang Sun ◽  
...  
Keyword(s):  
Near Infrared ◽  
Cooling System ◽  
Variable Temperature ◽  
Light Trapping ◽  
Nanowire Array ◽  
Infrared Light ◽  
Laser Source ◽  
Array Detector ◽  
Weak Light ◽  
Gap States

AbstractA simple fabrication of end-bonded contacts InAsSb NW (nanowire) array detector to weak light is demonstrated in this study. The detector is fabricated using InAsSb NW array grown by molecular beam epitaxy on GaAs substrate. The metal-induced gap states are induced by the end-bonded contact which suppresses the dark current at various temperatures. The existence of the interface dipole due to the interfacial gap states enhances the light excitation around the local field and thus upgrades the photoresponsivity and photodetectivity to the weak light. The light intensity of the infrared light source in this report is 14 nW/cm2 which is about 3 to 4 orders of magnitude less than the laser source. The responsivity of the detector has reached 28.57 A/W at room temperature with the light (945 nm) radiation, while the detectivity is 4.81 × 1011 cm·Hz1/2 W−1. Anomalous temperature-dependent performance emerges at the variable temperature experiments, and we discussed the detailed mechanism behind the nonlinear relationship between the photoresponse of the device and temperatures. Besides, the optoelectronic characteristics of the detector clarified that the light-trapping effect and photogating effect of the NWs can enhance the photoresponse to the weak light across ultraviolet to near-infrared. These results highlight the feasibility of the InAsSb NW array detector to the infrared weak light without a cooling system.

Application of FT-Raman spectroscopy to the study of selected organometallic complexes and proteins

1990 ◽  
Vol 68 (7) ◽  
pp. 1196-1200 ◽  
Author(s):  
Steven M. Barnett ◽  
François Dicaire ◽  
Ashraf A. Ismail
Keyword(s):  
Raman Spectroscopy ◽  
Near Infrared ◽  
Metal Carbonyl ◽  
Protein A ◽  
Organometallic Complexes ◽  
Laser Source ◽  
Chromium Tricarbonyl ◽  
Ft Raman Spectroscopy ◽  
Arene Chromium Tricarbonyl ◽  
Ft Raman

The study of colored organometallic complexes by dispersive Raman spectroscopy has been limited due to fluorescence or photodecomposition caused by the visible laser used as the excitation source. As a solution to this problem, FT-Raman spectroscopy with a near-infrared laser source has been useful in lowering fluorescence or photolysis in these samples. To investigate the utility of this technique, we have obtained and assigned the FT-Raman spectra of a series of arene chromium tricarbonyl complexes and of cyclopentadienyl manganese tricarbonyl. Some bands previously unobserved by dispersive Raman spectroscopy were seen, including a band assigned to a 13CO satellite in the spectrum of methylbenzoate chromium tricarbonyl. In addition, FT-Raman data for bovine serum albumin (BSA) and Protein-A are presented. Keywords: FT-Raman spectroscopy, metal carbonyl, proteins, organometallics, near infrared.

ORIENTATING MANIPULATION OF CYLINDRICAL PARTICLES WITH OPTICAL TWEEZERS

2008 ◽  
Vol 17 (04) ◽  
pp. 387-394 ◽  
Author(s):  
XIUDONG SUN ◽  
XUECONG LI ◽  
JIANLONG ZHANG
Keyword(s):  
Escherichia Coli ◽  
Carbon Nanotubes ◽  
Laser Beam ◽  
Optical Tweezers ◽  
Optical Trap ◽  
Polarization Direction ◽  
Beam Shape ◽  
E Coli ◽  
Potential Applications ◽  
Cylindrical Particles

Orientating manipulations of cylindrical particles were performed by optical tweezers. Vertical and horizontal manipulations of Escherichia coli (E. coli) were carried out by changing the trapping depth and the focused laser beam shape. It was found that carbon nanotubes bundles (CNTBs) could be rotated in the linear polarized optical trap until it orientated its long axis along the linear polarization direction of the laser beam. However, E.coli could not be orientated in this way. Corresponding mechanisms were discussed based on the anisomeric electric characters of CNTBs. These orientation technologies of cylindrical objects with optical trap have potential applications in assembling nano-electric devices.

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