A STUDY OF FEMTOSECOND LASER POLISHING OF CVD NANOPOLYCRYSTALLINE DIAMOND FILMS

2021 ◽  
pp. 2150023
Author(s):  
YU-XIAO CUI ◽  
PING GUO ◽  
XUEMING ZHU ◽  
YAN-LING TIAN ◽  
DA-WEI ZHANG ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Laser Fluence ◽  
Diamond Films ◽  
Chemical Vapor ◽  
Laser Pulses ◽  
Promising Technique ◽  
Laser Polishing ◽  
Laser Fluences ◽  
Fs Laser ◽  
The Mean

Femtosecond (fs) laser ablation has been recognized as an effective and promising technique for high-precision processing of natural and synthesized diamond. In this work, a study of femtosecond laser polishing for nanopolycrystalline diamond (NCD) films by chemical vapor deposition (CVD) is reported. The laser irradiation is induced by 200-fs laser pulses with a repetition frequency of 50[Formula: see text]MHz, and various laser fluences are employed to investigate their polishing effectiveness. The results show that the optimal laser fluence is 0.7[Formula: see text]J/cm2, at which the nanodiamond grains on top of the cauliflower-like clusters of NCD films can be ablated. With such laser fluence, the mean surface roughness of NCD films reduces from 73.84[Formula: see text]nm to 31.88[Formula: see text]nm, which presents a 57% reduction. Nevertheless, when the laser fluence rises beyond 0.7[Formula: see text]J/cm2, large amount of amorphous carbon (a-C) balls and porous lava-like morphology would come into being, resulting in severe degradation of the NCD surface.

Fabrication and Characterization of Si Nano-Columns by Femtosecond Laser

2012 ◽  
Vol 16 ◽  
pp. 15-20 ◽  
Author(s):  
Omid Tayefeh Ghalehbeygi ◽  
Vural Kara ◽  
Levent Trabzon ◽  
Selcuk Akturk ◽  
Huseyin Kizil
Keyword(s):  
Laser Ablation ◽  
Femtosecond Laser ◽  
Laser Beam ◽  
Chemical Etching ◽  
Silicon Surface ◽  
Laser Pulses ◽  
Laser Beam Profile ◽  
Fs Laser ◽  
Fabrication And Characterization

We fabricated Si Nano-columns by a femtosecond laser with various wavelengths and process parameters, whilst the specimen was submerged in water. The experiments were carried out by three types of wavelengths i.e. 1030 nm, 515nm, 343nm, with 500 fs laser pulses. The scales of these spikes are much smaller than micro spikes that are constructed by laser irradiation of silicon surface in vacuum or gases like SF6, Cl2. The Si nano-columns of 300 nm or less in width were characterized by SEM measurements. The formation of these Si Nano-columns that were revealed by SEM observation, indicates chemical etching with laser ablation occurred when surface exposed by laser beam. We observed 200 nm spikes height at the center of laser beam profile and the ones uniform in height at lateral incident area.

Ablation Dynamics of Silicon by Femtosecond Laser and the Role of Early Plasma

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
X. Zhao ◽  
Y. C. Shin
Keyword(s):  
Femtosecond Laser ◽  
Laser Fluence ◽  
Energy Transport ◽  
Femtosecond Laser Ablation ◽  
Heat Diffusion ◽  
Photon Absorption ◽  
Ablation Efficiency ◽  
Two Photon Absorption ◽  
Laser Fluences ◽  
Plasma Absorption

In this paper, the femtosecond laser ablation of silicon is investigated by a two-dimensional hydrodynamic model. The ablation depth of the silicon wafer ablated in air at different laser intensities is calculated, and the corresponding experimental measurements are carried out for validation. Two different ablation regimes have been identified by varying the laser fluence. While two-photon absorption dominates in the low fluence regime (<2 J/cm2), electron heat diffusion is a major energy transport mechanism at higher laser fluences (>2 J/cm2). The ablation efficiency first increases with the laser fluence, and reaches the peak value at the laser fluence around 8 J/cm2. It starts to drop when the laser fluence further increases, because of the early plasma absorption of the laser beam energy.

scholarly journals Transient Absorption Phenomena in Synthetic HPHT and CVD Diamonds for a Fast Timing in Nuclear Instrumentation

2017 ◽  
Vol 26 (3) ◽  
pp. 253
Author(s):  
O. Buganov ◽  
S. Tikhomirov ◽  
E. Barbarchik ◽  
M. Korjik ◽  
A. Fedorov ◽  
...  
Keyword(s):  
Transient Absorption ◽  
Chemical Vapor ◽  
Laser Pulses ◽  
Linear Absorption ◽  
Transient Phenomena ◽  
Synthetic Diamonds ◽  
High Pressure High Temperature ◽  
Pump And Probe ◽  
Fs Laser ◽  
Short Laser Pulses

In this study, we investigate  transient phenomena in synthetic diamonds  obtained by High Pressure High Temperature and Chemical Vapor Deposition methods. Study was aimed at searching for inorganic crystalline media combining ionizing radiation detecting properties and non-linear absorption of ultra-short laser pulses. The nonlinear pump-and-probe optical absorption technique with of 140 fs laser pulses was used to study the effects.

Femtosecond Laser Pulses Propagation in the inhomogeneous Gas Media

2021 ◽  
Author(s):  
Katsiaryna Cidorkina ◽  
Natalia Dorozhko ◽  
Alexander Svetashev ◽  
Leonid Turishev
Keyword(s):  
Laser Pulse ◽  
Femtosecond Laser ◽  
Femtosecond Laser Pulse ◽  
Pulse Shape ◽  
Pulse Propagation ◽  
Laser Pulses ◽  
The Media ◽  
The Mean ◽  
Inhomogeneous Gas ◽  
Stimulated Raman

&lt;p&gt;The present study is devoted to the numerical simulation and analysis of the high-intensity femtosecond LIDAR pulses propagation in the air with a special emphasis on the stimulated Raman scattering (SRS) and the stimulated Raman self-mode (SRSM) processes in optically inhomogeneous gas media.&lt;/p&gt;&lt;p&gt;Numerical models have been developed on the basis of a semi-classical energetic and wave theory, including a set of wave and material equations which allow simulating the gas mixtures, regular or stochastic density inhomogeneity and aerosol particles impact on the femtosecond laser pulse shape and spectrum.&lt;/p&gt;&lt;p&gt;The propagation of laser pulses (&amp;#955; = 400, 800 nm; &amp;#964; = 1 &amp;#247; 30 fs) with positive or negative chirp was numerically investigated in pure gases: H&lt;sub&gt;2&lt;/sub&gt;, N&lt;sub&gt;2&lt;/sub&gt;, O&lt;sub&gt;2&lt;/sub&gt; and their typical atmospherically mixtures.&amp;#160; &amp;#160;&lt;/p&gt;&lt;p&gt;The media density or composition (aerosol) inhomogeneity was simulated depending on the ratio between the path length (D), the size of the inhomogeneity (l) and the mean wavelength of pulse spectrum (&amp;#955;). For D &gt;&gt; l the inhomogeneity impact was considered as a stochastic, while in the case of D &lt; l the inhomogeneity was simulated having a constant gradient along the pulse track.&amp;#160; &amp;#160;&amp;#160;&amp;#160;&amp;#160;&lt;/p&gt;&lt;p&gt;For vertical sounding tracks the real atmospheric air density profiles were used.&lt;/p&gt;&lt;p&gt;Aerosol density and size fluctuations were estimated as 5&amp;#247;30% to the mean value.&lt;/p&gt;&lt;p&gt;In model testing regime the SRS and SRMS modes of the femtosecond laser pulse propagation for tracks of up to 100 m have been calculated for investigating the dynamics of the pulse shape, spectrum and energy change under different initial conditions.&lt;/p&gt;&lt;p&gt;The SRMS mode for 10, 14 and 20 fs laser pulses with energy areas of 3&amp;#960;, 2&amp;#960;, &amp;#960;, &amp;#960;/100 was numerically investigated in different gas and aerosol compositions for tracks of &amp;#946;z = 0.5 &amp;#247; 20, where z is the space coordinate and &amp;#946; &amp;#8211; the inverse value of Raman self-scattering defined by the media.&amp;#160;&lt;/p&gt;&lt;p&gt;The results obtained show that the dynamics of pulse propagation in SRMS mode is nonlinear in the pulse shape and spectrum. Moreover, the SRMS mode having a resonance character for 2&amp;#960;-pulses may be misaligned as well as modulated by the inhomogeneity of the medium.&lt;/p&gt;

scholarly journals Ultrafast dynamical process of Ge irradiated by the femtosecond laser pulses

2016 ◽  
Vol 4 ◽  
Author(s):  
Fangjian Zhang ◽  
Shuchang Li ◽  
Anmin Chen ◽  
Yuanfei Jiang ◽  
Suyu Li ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Pulse Duration ◽  
Laser Fluence ◽  
Carrier Density ◽  
Laser Intensity ◽  
Great Influence ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses ◽  
Lattice Temperature ◽  
Dynamical Process

The ultrafast dynamic process in semiconductor Ge irradiated by the femtosecond laser pulses is numerically simulated on the basis of van Driel system. It is found that with the increase of depth, the carrier density and lattice temperature decrease, while the carrier temperature first increases and then drops. The laser fluence has a great influence on the ultrafast dynamical process in Ge. As the laser fluence remains a constant value, though the overall evolution of the carrier density and lattice temperature is almost independent of pulse duration and laser intensity, increasing the laser intensity will be more effective than increasing the pulse duration in the generation of carriers. Irradiating the Ge sample by the femtosecond double pulses, the ultrafast dynamical process of semiconductor can be affected by the temporal interval between the double pulses.

scholarly journals Laser Fluence Dependence of the Electrical Properties of MoO2 Formed by High Repetition Femtosecond Laser Pulses

2018 ◽  
Vol 215 (19) ◽  
pp. 1800226 ◽  
Author(s):  
Santiago Camacho-Lopez ◽  
Israel O. Perez-Lopez ◽  
Miroslava Cano-Lara ◽  
Alejandro Esparza-Garcia ◽  
M. Carmen Maya-Sanchez ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Femtosecond Laser ◽  
Laser Fluence ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses ◽  
High Repetition ◽  
Fluence Dependence

Fabrication of high-aspect-ratio grooves with high surface quality by using femtosecond laser

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ru Zhang ◽  
Chuanzhen Huang ◽  
Jun Wang ◽  
Hongtao Zhu ◽  
Hanlian Liu
Keyword(s):  
Laser Ablation ◽  
Aspect Ratio ◽  
Femtosecond Laser ◽  
Process Parameters ◽  
Laser Fluence ◽  
High Aspect Ratio ◽  
High Surface ◽  
Content Type ◽  
High Surface Quality ◽  
Fs Laser

Purpose The purpose of this study is to fabricate high-aspect-ratio grooves with high surface quality by femtosecond laser (FS) to improve the machinability of silicon carbide (SiC) and optimize the process parameters in micromechanical applications. Design/methodology/approach Four contrast experiments are reported to characterize the FS laser grooving process for SiC with polarization direction, crystal orientation, multi-pass scanning and z layer feed, respectively. The effects of different experimental conditions on the groove characteristics, material removal rate (MRR), aspect ratio, heat affected zone (HAZ) and surface roughness Ra are analyzed. Findings The influence of increasing laser fluence and multi-scanning pass on the groove depth is greater than on the groove width. The MRR, aspect ratio, HAZ and Ra increased with the increase of laser fluence and multi-scanning pass. The direction of laser polarization affects the direction of hot electron injection but has little effect on the material characteristics. FS laser ablation is an isotropic process and there is no obvious change in different crystal orientations. The z-layer feed can significantly increase the groove width and depth and reduce HAZ and Ra. The maximum aspect ratio of 82.67% was fabricated. Originality/value The results contribute to the understanding of the removal mechanism and reduce the friction of the microfluidic device and improve the flowability in the FS laser ablation of SiC. This paper provides suggestions for the selection of suitable process parameters and provides a wider possibility for the application of micro-texture on SiC.

Photoionization Yields in Intense fs-Laser Fields – A Systematic Investigation of Chirp Effects

2015 ◽  
Vol 229 (10-12) ◽  
Author(s):  
Nicola Reusch ◽  
Steffen Griebe ◽  
Johannes Karges ◽  
Karl-Michael Weitzel
Keyword(s):  
Femtosecond Laser ◽  
Laser Pulses ◽  
Systematic Investigation ◽  
Spectral Phase ◽  
Second Order ◽  
Laser Ionization ◽  
Laser Fields ◽  
Linear Chirp ◽  
Fs Laser ◽  
Hydrocarbon Molecules

AbstractThe femtosecond laser ionization of several small hydrocarbon molecules (methane, ethane, propane) has been investigated as a function of the second order spectral phase (linear chirp) of laser pulses centered at

Femtosecond Laser Ablation of Titanium and Silicon

2000 ◽  
Author(s):  
Mengqi Ye ◽  
Costas P. Grigoropoulos
Keyword(s):  
Laser Ablation ◽  
Femtosecond Laser ◽  
Laser Fluence ◽  
Laser System ◽  
Femtosecond Laser Ablation ◽  
Laser Pulses ◽  
Femtosecond Laser Irradiation ◽  
Nanosecond Laser ◽  
Iccd Camera ◽  
Plume Emission

Abstract Femtosecond laser ablation of titanium and silicon samples has been studied via time-of-flight (TOF), emission spectroscopy and microscopy measurement. Laser pulses of around 100 fs (FWHM) at λ = 800 nm were delivered by a Ti:sapphire femtosecond laser system. A vacuum chamber with a base pressure of 10−7 torr was built for ion TOF measurement. These ion TOF spectra were utilized to determine the velocity distribution of the ejected ions. While nanosecond laser ablation typically generates ions of a few tens of eV, femtosecond laser irradiation even at moderate energy densities can produce energetic ions with energies of up to a few keV. The most probable energy of these fast ions is proportional to the laser fluence. The structure and number of peaks of the TOF spectra varies with the laser fluence. Images of plume emission were captured by an intensified CCD (ICCD) camera. The plume emission spectrum was analyzed by a spectrometer. Laser ablated craters were measured by an interferometric microscope and a scanning electron microscope (SEM). Ablation yield was expressed as a function of laser fluence, and number of shots.

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