Direct Femtosecond Laser Surface Structuring with Optical Vortex Beams Generated by a q-plate

Nivas, Jijil Jj; He, Shutong; Rubano, Andrea; Vecchione, A.; Paparo, D.; Marrucci, Lorenzo; Bruzzese, R.

doi:10.1038/srep17929

Cited by 127 publications

(94 citation statements)

References 28 publications

(70 reference statements)

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“…only related with the pronounced enhanced ripple periodicity or depth due to the dissimilar spatial profile of the deposited energy but also with a different orientation of the produced profile. More specifically, the ripple formation induced by RP (see Fig.10 for NP=2) are concentric periodic structures that have also been observed experimentally in previous works 17,33,35,40,41 . Indeed, a simulated two-dimensional pattern that is illustrated in Fig.10a shows the surface profile while the height distribution is shown in Fig.10b.…”

Section: Resultssupporting

confidence: 82%

“…It was shown that the spatial form of the RP does not only lead to structures of different periodicity compared to those induced if LP beams are used ( Fig.9) but also produce structures of (spatially) variable height ( Fig.7-8) and spatial distribution (Fig.10b). This is a significant prediction (which was verified experimentally for Ni in a previous work 33,35 or semiconductors 40,41 ) as it demonstrates the capability of controlling characteristics of morphological features with the use of different polarization states. It should be mentioned, though, that a systematic experimental validation of the numerical results is required to confirm the accuracy of the proposed model for irradiation of noble metals with small electron-phonon coupling constant.…”

Section: Resultssupporting

confidence: 72%

“…Based on Eq. (1), the radially polarized beam has a 4 maximum intensity (corresponding to the peak fluence) at r=R 0 with value ~  2 1 e / 4 22 ~0 .74 where R 0 stands for the irradiation spot radius (R 0 =7μm in Fig.1), similar to that used in recent works 40,41 . In both types of polarization, the same total laser beam energy is assumed.…”

Section: A Polarisation Of the Laser Beammentioning

confidence: 92%

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Ripple formation on silver after irradiation with radially polarised ultrashort-pulsed lasers

Tsibidis

Stratakis

2017

Journal of Applied Physics

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We report on the morphological effects induced by the inhomogeneous absorption of cylindrically polarized femtosecond laser irradiation of silver (Ag) in sub-ablation conditions. A theoretical prediction of the role of surface plasmon excitation and thermal effects in the production of self-formed periodic ripples structures is evaluated. To this end, a combined hydrodynamical and thermoelastic model is presented to account for the influence of temperature-related lattice movements in laser beam conditions that are sufficient to produce material melting. Results indicate that material displacements due to hydrodynamics are substantially larger than strain-related movements which also emphasises the predominant role of fluid transport in surface modification. Moreover, theoretical simulations highlight the influence of the polarisation state in the size of the ripple periodicity for a specialized case of cylindrically polarized beams, the radially polarized beams. Results show that the ripple periodicity is larger than if linearly polarized beams are used. This is the opposite trend to the behaviour for materials with decreasing electron-phonon coupling constant g with increasing electron temperature which highlight the significant role of g.2 On the other hand, cylindrical vector beams (CVB) have recently gained remarkable attention as the symmetry of the polarization enables new processing strategies 23 with applications in various fields including microscopy, lithography 24 , electron acceleration 25 , material processing 23,26,27 and optical trapping 28 . The cylindrical vector polarization states have been the topic of numerous theoretical and experimental investigations 26,[29][30][31][32] and they are also characterized by a great potential to provide a plethora of complex structures and biomimetic surfaces 33 with a wide range of applications 34 .Recently, the mechanism of LIPSS formation on transition metals (i.e. nickel) upon femtosecond irradiation with CVB was explored systematically and the comparison with results derived by linearly polarized beams were highlighted 35 . While a combination of electrodynamic (i.e. related to surface plasmon excitation) and temperature gradient related effects were proposed to explain the periodically modulated surface for nickel which is a material characterized with strong electron-phonon coupling constant g, it is equally important to investigate whether metals with relatively smaller g also demonstrate similarly pronounced morphologies. This is due to the fact that the magnitude of g determines the efficiency/speed with which electron energy is transferred to the lattice system (i.e. strong coupling strength implies larger energy transfer from the hot electrons to lattice and therefore thermalisation between electron and lattice systems occurs faster). It is known that smaller electron-phonon coupling strengths are expected to lead to less pronounced ripples for linearly polarized beams for noble metals 36,37 . Hence, it is evident that more intense beams or increa...

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Section: Resultssupporting

confidence: 82%

Section: Resultssupporting

confidence: 72%

Section: A Polarisation Of the Laser Beammentioning

confidence: 92%

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Ripple formation on silver after irradiation with radially polarised ultrashort-pulsed lasers

Tsibidis

Stratakis

2017

Journal of Applied Physics

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“…More specifically, laser beams with cylindrical states, namely radial and azimuthal polarization, have gained considerable attention in the past two decades, as the symmetry of the polarization enables new processing strategies [17] with applications in various fields including microscopy, lithography [18], electron acceleration [19], material processing [17,20,21] and optical trapping [22]. The so-called cylindrical vector beams (CVB) have been the topic of numerous theoretical and experimental investigations [20,[23][24][25][26][27][28][29]. A recent work on nickel irradiation with femtosecond pulses revealed morphological changes for LPB and CVB for various fluences and number of pulses [30].…”

Section: Introductionmentioning

confidence: 99%

Formation of periodic surface structures on dielectrics after irradiation with laser beams of spatially variant polarisation: a comparative study

et al. 2018

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A comparative study is performed to explore the periodic structure formation upon intense femtosecond pulsed irradiation of dielectrics with radially and azimuthally polarised beams. Laser conditions have been selected appropriately to produce excited carriers with densities below the optical breakdown threshold in order to highlight the role of phase transitions in surface modification mechanisms. The frequency of the laser induced structures is calculated based on a theoretical model that comprises estimation of electron density excitation, heat transfer, relaxation processes, and hydrodynamics-related mass transport. The influence of the laser wavelength in the periodicity of the structures is also unveiled. The decreased energy absorption for azimuthally polarised beams yields periodic structures with smaller frequencies which are more pronounced as the number of laser pulses applied to the irradiation spot increases. Similar results are obtained for laser pulses of larger photon energy and higher fluences. All induced periodic structures are oriented parallel to the laser beam polarisation.

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“…This fact potentially increases the overall system capacity by using multiple OAM states in conjunction with other multiplexing techniques such as WDM and PDM since it is independent of wavelength and polarization. Not only optical communication, there are various applications of OAM beams highlighted in the reference 3) such as optical tweezing, 4,5) laser material surface processing, 6,7) quantum entanglement, 8,9) image processing, 10) and quantum metrology.…”

Section: Introductionmentioning

confidence: 99%

Mode sorting performance for optical beams carrying orbital angular momentum suffering lateral displacement and angular deflection

Kishikawa¹,

Sakashita²,

Goto³

2018

Jpn. J. Appl. Phys.

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Beams carrying orbital angular momentum (OAM) is expected to be a new degree of multiplexing to increase transmission capacity in the optical communication. Mode sorting methods have been reported so far as efficient ways to demultiplex such OAM multiplexed lightwaves. Since the OAM transmission is mainly through free-space, the transmitting OAM lightwave may suffer lateral displacement and angular deflection on the receiver plane. In this paper, we numerically investigate the tolerance to lateral displacement and angular deflection on the mode sorting performances for beams carrying OAM. Comparing the performance in terms of crosstalk in between high resolution and ordinary resolution mode sorting methods reveals that the high resolution one shows a slight lower crosstalk while almost the same tolerance as the ordinary resolution one.

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Direct Femtosecond Laser Surface Structuring with Optical Vortex Beams Generated by a q-plate

Cited by 127 publications

References 28 publications

Ripple formation on silver after irradiation with radially polarised ultrashort-pulsed lasers

Ripple formation on silver after irradiation with radially polarised ultrashort-pulsed lasers

Formation of periodic surface structures on dielectrics after irradiation with laser beams of spatially variant polarisation: a comparative study

Mode sorting performance for optical beams carrying orbital angular momentum suffering lateral displacement and angular deflection

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