Laser Etching Technique Research Articles

Numerical and experimental investigations into microchannel formation in glass substrate using electrochemical discharge machining

Microchannels formed in non-conductive substrates like fused silica, glass and quartz, etc, have wide applications in the field of micro-fluidic and lab-on-chip applications due to their optical transparency, chemical inertness, and biocompatible nature. Electrochemical discharge machining (ECDM) has emerged as a potential low-cost fabrication method to fabricate microfeatures in these materials, compared to conventional laser etching techniques. In this paper, numerical simulation and experimental fabrication of microchannels in a glass substrate using the ECDM based micromilling technique is demonstrated. Stainless steel needle as tool electrode is used in alkaline electrolyte medium. The effects of process parameters viz. tool feed rate, pulse frequency and machining voltage on material removal rate (MRR) and surface roughness (SR) of the microchannels were analysed. The experimental results showed that the MRR and SR increases with an increase in machining voltage and tool feed rate but reduces with an increase in the pulse frequency. Simulations using FEM-based model showed similar trends in MRR with that of experiments. A comparison between the cross-section profiles obtained by the experimental work and predicted profile by the numerical simulation showed some deviation between them due to the Gaussian heat flux assumption in the numerical model. Optical images showed that KOH performance is comparatively better than NaOH with respect to thermal damage and width of cut. Further, multi-objective optimization was performed using utility theory coupled with Taguchi’s method to optimize the process parameters. Moreover, the capability of the ECDM process was demonstrated in fabricating various other micro-features such as sinusoidal channel, letter engraving, etc in a glass substrate, which can be extended to other brittle materials like quartz, fused silica, ceramic, etc.

Lateral mode engineering in diode lasers based on coupled ridges

We present an experimental study on the edge-emitting lasers based on coupled ridges. The main idea of these structures is to ensure fundamental mode lasing in broadened multi-mode ridges by means of using a high-order mode filtering based on the resonant optical tunneling into a nearby passive stripe. For our experiments, we used a conventional InAs/InGaAs quantum dot (QD) laser wafer (λ∼1.28μm) and placed a 3 μm passive dielectric-covered ridge at the distance of 4 μm from 10 μm main active ridge. The devices demonstrated stable far-field patterns with suppressed first-order mode lasing and without any deterioration of the main laser parameters. However, side lobes in the far-field patterns indicated second-order mode traces attributed to the current spread from the main stripe, which increase the effective stripe width. We assume that optimization of the laser hafer and etching technique may lead to a pure lateral single-mode lasing in the coupled ridge devices.

A glassy carbon electrode modified with a bismuth film and laser etched graphene for simultaneous voltammetric sensing of Cd(II) and Pb(II)

Polyimide (PI) sheets were laser etched to obtain graphene-based carbon nanomaterials (LEGCNs). These were analyzed by scanning electron microscopy, X-ray diffraction and Raman spectroscopy which confirmed the presence of stacked multilayer graphene nanosheets. Their large specific surface and large number of edge-plane active sites facilitate the accumulation of metal ions. A glassy carbon electrode (GCE) with an in-situ plated bismuth film was modified with the LEGCNs to give a sensor with satisfactory response for the simultaneous determination of cadmium(II) and lead(II) by means of square wave anodic stripping voltammetry. It appears that is the first report on an electrochemical sensor based on the use of laser etched graphene for determination of heavy metal ions. Figures of merit for detection of Cd(II) include (a) a low and well separated working potential of -0.80V (vs. Ag/AgCl), (b) a wide linear range (from 7 to 120μg·L-1), and a low detection limits 0.47μg·L-1. The respective data for Pb(II) are (a) -0.55V, (b) 5 to 120μg·L-1, and (c) 0.41μg·L-1. The modified GCE displays remarkable repeatability, reproducibility, selectivity and stability. The sensor was applied to the simultaneous determination of Cd(II) and Pb(II) in spiked real water samples. The results confirm that the laser etching technique is an efficient tool for the preparation of carbon nanomaterials with high quality and great sensing performance. Graphical abstract Bismuth film and laser etched graphene-modified glassy carbon electrode (BF-LEGCN/GCE) for the simultaneous determination of cadmium(II) and lead(II) by square wave anodic stripping voltammetry.

Effects of a low-pressure water jet assisting the laser etching of polycrystalline silicon

Laser micromachining has proven to be a useful tool for the precision processing of semiconductors. In the hybrid laser–water jet micromachining process investigated in this research, a laser is used for heating and softening the work material (polycrystalline silicon, in this case), while a water jet is employed for shearing the softened material and subsequently removing it due to the high-velocity of the liquid jet impingement, as well as for cooling the material. Specifically, the use of a low-pressure water jet to assist with the laser etching of polycrystalline silicon was investigated in this study. The energy efficiency of the processing as well as the width, depth, and surface microstructure of the groove etched in the polycrystalline silicon using the composite process were considered. With increasing jet velocity, the integrated energy initially decreased before increasing and the overall groove depth decreased, then increased, and finally decreased again. When the incidence angle was 30°, the groove width in the polypolycrystalline silicon increased as the jet velocity increased from 8 and 28 m s−1, and the use of a low-pressure jet to assist with the laser etching resulted in etched surfaces smoother than those obtained in air and hydrostatic conditions. The experimental results prove that the low-pressure water-jet-assisted laser etching technique can overcome the problems of micro-crack, slag, and recast layer formation that affect traditional laser etching and consequently improve the quality of machined parts.

Enhanced Photoluminescence of Solution-Exfoliated Transition Metal Dichalcogenides by Laser Etching.

Using a conventional Raman experimental apparatus, we demonstrate that the photoluminescent (PL) yield from ultrasonication-exfoliated transition metal dichalcogenides (TMDs) (MoS2 and WS2) can be increased by up to 8-fold by means of a laser etching procedure. This laser etching process allows us to controllably pattern and reduce the number of layers of the solution-exfoliated material, overcoming the key drawback to solvent-based exfoliation of two-dimensional (2D) semiconducting materials for applications in optoelectronics. The successful laser thinning of the exfoliated 2D crystals was investigated systematically by changes in both Raman and PL spectra. A simple proof-of-principle of the scalability of this laser etching technique for solution-exfoliated TMD crystals was also demonstrated. As well as being applicable for individual materials, it is also possible to use this simple laser etching technique to investigate the structure of solution-generated van der Waals heterostructures, consisting of layers of both MoS2 and WS2.

Clarification of Colloidal Particles in Lake and River Water Using AC Electrokinetic

Scenery of clear water of a lake or river is always a fascinating view. The clarity of a water is subjected to the water free from colloidal particles. Lake or river usually have foreign colloidal particles such as sand, mud, foreign particle, etc. which make the water cloudy. Usually the cloudy water become clear because of natural sedimentation process. However it is not easy to clarify cloudy water of a lake or river and make it clear especially if the sediment of colloidal particle is influence or disturb by water current. The approach by AC Electrokinetic phenomenon able to manipulate colloidal particles in a suspension. It can separate, trap or sort colloidal particle which made the phenomenon as possible reliable option for clarifying lake or river water from colloidal particles hence make it clear water. This work will simulate the process of clarification of colloidal suspension using AC Electrokinetic phenomenon in a lab. Electrodes were fabricated on Indium Tin Oxide (ITO) coated glass slide using laser etching technique. The electrode which poses unique geometry will be able to demonstrate electric field gradient as soon as it is introduced with electrical signal. Base on the surface potential of the colloids and the surface potential of the electrode, the colloids will be manipulated. This phenomenon is known as AC Electrokinetics. This can be regarded as guided sedimentation process. The trapped colloidal particle can be now easily extracted or remove from the water thus transform the water from cloudy to clear hence complete water clarification process.

Hybrid Laser-Etching-Process for Wafer Texturing

An approach of a texturing process combining surface modification by ultra-short pulsed laser radiation and etching techniques is developed. The hybrid process is divided into two steps: Firstly, the surface of a silicon wafer is modified by laser radiation. For this purpose, the influence of several laser parameters, e.g. wavelength, pulse duration and energy density, have been analyzed. Secondly, the surface texture is fabricated by an etching process.The modification threshold of the laser treatment is determined for different silicon materials. Different surface modifications occur for different materials after applying the laser treatment. No significant influence of the pulse duration or focus radius is found.Furthermore, the influence of laser processing and plasma etching on reflectivity spectra is compared and interactions between laser and etching parameters are investigated. The developed hybrid process results in smooth and fine surface microstructures. First results show a reduction of the reflectivity in the range of 30% compared to the reflectivity of unstructured wafers.

NIR Luminescence from Sol-Gel Er3+Doped SiO2:GeO2Transparent Gels, Nanostructured Powders and Thin Films for Photonic Applications

Samples of (1 – x)SiO2:xGeO2 compositions, containing x = 10 and 20, and doped with Er3+, were prepared by a simple sol-gel route. Homogeneous and transparent gels were synthesized and xerogels were obtained by gel annealing from 700 oC to 1100 oC. Films exhibiting high transmittance in the visible and near infrared were deposited by spin-coating technique using the colloidal precursors. The materials were characterized structurally and microstructurally by some techniques. Spherical completely amorphous and tetragonal GeO2 nanocrystals from 3.7 nm to 25.0 nm in diameter embedded in silica-rich amorphous phase materials were obtained. The optical properties were studied by transmission spectra from ultraviolet to near infrared region, photoluminescence measurements in the infrared region, and the average lifetime of the metastable state 4I13/2 of Er3+ ions were determined. The 1 mol% Er3+ doped host with x = 20 have an infrared emission 4.9 times higher than the compound containing x = 10, and the Er3+4I13/2 level present lifetime between 15.0 ms and 7.5 ms. The optical band gap and refractive index values were determined, as well as the Sellmeier parameters. Finally, rib channel waveguides using femtosecond laser etching technique on silica substrates were obtained with width of 15 mm. The 1 mol% Er3+ doped 80SiO2:20GeO2 compounds can be applicable in integrated optical systems.

Laser etching technique using bubble jet impact for glass substrates

The purpose of this paper is to propose a new laser etching technique using bubble jet impact for glass substrates. An Nd:YAG laser is applied to the backside of the substrate which is partially submerged in water. A metal plate is placed below the glass substrate. The metal vaporizes the water and generates a turbulent bubble flow. The bubble nozzle is proposed to enhance the impact of the bubble jet. The glass surface will first be softened, and then expelled by the shock wave resulting from the jet impact. The phenomena of bubble nucleation, growth, collapse, and jet impact were studied in this paper. The formation of the etching cavity can be divided into three types: double-petal, triple-petal, and four-petal. The etching pits expanded and combined to form a complete cavity. The needed laser power does not exceed 5 W. The proposed laser etching method was successfully demonstrated for etching a cavity of 5–20 µm in depth and 50–250 µm in diameter. The bubble jet of the small nozzle diameter is well concentrated, creating a strong jet impact on the glass surface. A greater nozzle depth can enhance the impact of the bubble jet. The proposed etching technique has great potential to provide an improved solution for the micro-machining of glass.

Low-cost photomask fabrication using laser ablation

A specific fabrication process has been developed to produce low-cost photomasks using standard consumer products. This process is based on an indirect route, using a numerically controlled excimer laser (KrF) etching technique. It begins with RF-sputtering deposition of a titanium film (200nm-thick) on float glass substrate. Then a nitrocellulose lacquer, serving as a self-developing resist, is spin-coated on titanium. It is ablated with partially overlapping laser impacts and undergoes self-combustion under laser beam. Proper heat treatments are applied before and after laser ablation to circumvent smearing and adhesion problems. Finally the titanium layer is wet etched through the openings in the resist by dilute hydrofluoric acid. Both nitrocellulose lacquer characterization and laser parameters are discussed. The resolution achieved here (10μm, limited by diffraction effects of the laser optics and by side heating of the resist due to the titanium film) is suitable for the fabrication of microwave devices.To confirm the suitability of the proposed process, several photomasks have been fabricated to pattern coplanar tunable stub resonators on ferroelectric KTa0.5Nb0.5O3 thin films. The dielectric permittivity of the KTa0.5Nb0.5O3 material is controlled by DC biasing. A 18% tunability of the stub resonance frequency has been measured in X-band (close to 10GHz), validating thereby the whole patterning process.

Effects of laser dimple texturing on the sliding wear of friction pairs

In order to reduce the sliding wear of friction pairs under dry friction condition, the surfaces of friction pairs were textured with morphology of dimples using laser etching technique, and the influence of surface micromorphology on the wear rate of friction pairs was studied. The results show that the laser dimple texturing can reduce abrasive wear of the friction pairs when they were in rolling contact and sliding movements, the occurrence of pear-shaped ditches was eliminated and damage of the surface oxide layer was relieved. The well-preserved surface oxide layer would restrain the penetration of air oxygen molecules into the friction pair, thanks to the dense oxide layer, and thereby reduce the wear rate. For the friction pair textured with morphology of etched dimples, the oxide layer is well preserved, its wear rate is reduced, and the oxygen atomic mass percentage on the surface is rather low.

Physical modeling of anisotropic domains: Ultrasonic imaging of laser-etched fractures in glass

Many regions of subsurface interest are, or will be, fractured. Seismically characterizing these zones is a complicated but essential task for resource development. Physical modeling, using ultrasonic sources and receivers over scaled exploration targets, can play a useful role as an analog for reservoir imaging and assessment. We explored the anisotropic response of glass blocks containing internal fractures created by a novel laser-etching technique. We compared transmitted and reflected signals for P- and S-waves from fractured and unfractured zones in a suite of ultrasonic (1–5 MHz) experiments. The unaltered glass velocities have averages of [Formula: see text] and [Formula: see text] for P- and S-waves, respectively (giving [Formula: see text]). The unfractured glass has a very high quality (Q) factor of over 500 for P-waves and S-waves. The fractured zones have a small (up to 1.5%) velocity decrease. Signals propagating through the fractured zone have diminished amplitudes and increased coda signatures. Reflection surveys (zero-offset and with variable polarizations) record significant scatter from the fractured zones. The fracture-scattered energy can be migrated to provide a sharper image. The glass specimens with laser-etched fractures display a rich anisotropic response, which can help inform field-scale imaging.

NIR luminescent Er3+/Yb3+ co-doped SiO2–ZrO2 nanostructured planar and channel waveguides: Optical and structural properties

Optical and structural properties of planar and channel waveguides based on sol–gel Er3+ and Yb3+ co-doped SiO2–ZrO2 are reported. Microstructured channels with high homogeneous surface profile were written onto the surface of multilayered densified films deposited on SiO2/Si substrates by a femtosecond laser etching technique. The densification of the planar waveguides was evaluated from changes in the refractive index and thickness, with full densification being achieved at 900 °C after annealing from 23 up to 500 min, depending on the ZrO2 content. Crystal nucleation and growth took place together with densification, thereby producing transparent glass ceramic planar waveguides containing rare earth-doped ZrO2 nanocrystals dispersed in a silica-based glassy host. Low roughness and crack-free surface as well as high confinement coefficient were achieved for all the compositions. Enhanced NIR luminescence of the Er3+ ions was observed for the Yb3+-codoped planar waveguides, denoting an efficient energy transfer from the Yb3+ to the Er3+ ion.

Enhancing and broadening absorption properties of frequency selective surfaces absorbers using FeCoB-based thin film

In this paper, the influence of FeCoB-based magnetic film on the absorption properties of traditional frequency selective surface (FSS) was investigated experimentally. A single-layer Minkowski fractal planar frequency selective surface was chosen, and the laser etching technique was proposed to fabricate aluminum-based FSS (AFSS) samples. Magnetic films were prepared by radio frequency magnetron sputtering, with the targets of Fe40Co40B20 and SiO2. It is found that after the magnetic film is incorporated, the bandwidth under −10 dB increases by 33.3% from 5.08 to 6.78 GHz and the peak value of reflectivity decreases from −12.46 to −38.41 dB. The 3.1-mm-thick radar absorber is relatively light and could obtain the reflectivity of −38.41 with −20 dB bandwidth of 1.85 GHz. As a consequence, under the circumstance that the total thickness of the sample maintains relatively constant, the magnetic thin film can effectively improve the absorption properties of the sample.

Fabrication and analysis of transmission gratings produced by the indirect laser etching technique

The diffraction efficiency of gratings etched into fused silica was measured and modelled. 950, 2120 and 3710 nm period gratings were fabricated with the use of two-beam interferometric laser-induced backside wet etching (TWIN-LIBWE). The spatial distribution of the modulation depth (MD), determined from AFM measurements, followed the spatial intensity distribution of the laser beam throughout the grooved areas. The diffraction efficiency of the fabricated gratings was measured to all allowed diffraction orders at several wavelengths (266, 532 and 654.5 nm). Within the frame of Gsolver code, a model was developed that takes into account the spatial distribution of MD. The computed diffraction efficiencies showed good agreement with the results of measurements.

Laser versus conventional acid etching technique on bond strength of orthodontic brackets (An in vitro stydy)

Aims: This in vitro study was undertaken to evaluate and compare the effect of acid etching and/or diode laser (1064 nm) irradiation on shear bond strength of orthodontic brackets. Materials and Methods: Thirty freshly extracted human premolars were included in this study. Laser irradiation was done by using the new 1064 nm diode laser with output power of 2.5 Watt in continues mode, also use stainless steel orthodontic brackets (Roth, 22–slot size), and use orthodontic flowable composite resin which needs no bonding fluid. The 30 human teeth were divided into 3 groups (each group consist of 10 teeth): Group A–use acid etching (37% phosphoric acid) for 1 minute to bond bracket to tooth surface (control group), group B–use laser irradiation for 30 seconds with Indian ink (coated on teeth). Group C–use laser irradiation for 30 seconds with Indian ink after that use acid etching for 1 minute. Shear bond strength measured by using unconfined shear testing machine at a cross head speed of 5 mm/min. Results: The shear bond strength means were as follows: Group A: 11.27 MPa, group B: 6.21 MPa, group C: 14.04 MPa. The acid etching after 1064 nm diode laser irradiation (group C) has significantly higher bond strength (p
0.05) than remaining groups. In group B, orthodontic brackets had significantly lower shear bond strength (p
0.05) than remaining groups. Conclusions: These results indicate that acid etching after laser irradiation enhances and improves the bonding of orthodontic composite resin to human enamel. In the same time 1064 nm diode laser irradiation with ink coating is not consider as a replacement to acid etching in bonding of orthodontic brackets to human enamel.

Modified laser etching technique of enamel for bracket bonding

Modified laser etching technique of enamel for bracket bonding

Development of thick-foil and fine-pitch GEMs with a laser etching technique

We have produced thick-foil and fine-pitch gas electron multipliers (GEMs) using a laser etching technique. To improve production yield we have employed a new material, liquid crystal polymer, instead of polyimide as an insulator layer. The effective gain of the thick-foil GEM with a hole pitch of 140 μ m , a hole diameter of 70 μ m , and a thickness of 100 μ m reached a value of 10 4 at an applied voltage of 720 V. The measured effective gain of the thick-foil and fine-pitch GEM ( 80 μ m pitch, 40 μ m diameter, and 100 μ m thick) was similar to that of the thick-foil GEM. The gain stability was measured for the thick-foil and fine-pitch GEM, showing no significant increase or decrease as a function of elapsed time from applying the high voltage. The gain stability over 3 h of operation was about 0.5%. Gain mapping across the GEM showed a good uniformity with a standard deviation of about 4%. The distribution of hole diameters across the GEM was homogeneous with a standard deviation of about 3%. There was no clear correlation between the gain and hole diameter maps.

Investigation of sidewall roughness of the microgrooves manufactured with laser-induced etching technique

A novel laser etching technique utilizing an optical fiber as the laser beam guide is introduced. Depending upon whether a pulsed or a continuous wave (CW) laser is employed as the irradiation source, it was found that the etch depth and surface morphology of the grooves varied significantly. It was then demonstrated that deep microgrooves with smooth sidewalls can be obtained using a hybrid pulse and CW scanning process. The results of laser heating and chemical analyses revealed that sidewall roughness of the microgroove is mainly attributed to surface melting.

Structuring of nanoporous nickel-based superalloy membranes via laser etching

Structures with a very fine and regular porosity enable inventions or further developments of a multitude of components like substrate applications in fuel cell technology or catalytic reaction spaces in chemical reactors. Here we show a novel method for structuring nanoporous metal membranes to generate one-component modules with multi-functionality. For this purpose a combination of the laser etching and electrochemical-etching techniques is applied to directional coarsened nickel-based superalloys.