Optical determination of three-dimensional nanotrack profiles generated by single swift-heavy ion impacts in lithium niobate

Olivares, J.; García-Navarro, A.; Garcı́a, Gustavo; Mýndez, A.; Agulló‐López, F.

doi:10.1063/1.2236221

Cited by 29 publications

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“…The physical basis is as follows: Irradiation with mediummass ions having sufficiently high energy so that their electronic stopping power ͑S e ͒ is above a certain threshold value (S th Ϸ 5 -6 keV/ nm for LiNbO 3 ) generates amorphous tracks with a nanometric diameter [10][11][12][13]. Each track is associated with a single ion impact and presents [12,13] an isotropic refractive index (n a = 2.10 at = 633 nm). It has been shown [14] that for LiNbO 3 and many other oxides the radius R c ͑z͒ of the track at a depth z increases monotonically with the stopping power S e ͑z͒ Ͼ S th .…”

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“…It dramatically reduces the required ion fluences down to ϳ10 12 cm −2 , while essentially keeping the nonlinear optical performance. The physical basis is as follows: Irradiation with mediummass ions having sufficiently high energy so that their electronic stopping power ͑S e ͒ is above a certain threshold value (S th Ϸ 5 -6 keV/ nm for LiNbO 3 ) generates amorphous tracks with a nanometric diameter [10][11][12][13]. Each track is associated with a single ion impact and presents [12,13] an isotropic refractive index (n a = 2.10 at = 633 nm).…”

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Nonlinear optical waveguides generated in lithium niobate by swift-ion irradiation at ultralow fluences

et al. 2007

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A novel method to produce optical waveguides is demonstrated for lithium niobate ͑LiNbO 3 ͒. It is based on electronic excitation damage by swift ions, i.e., with energies at approximately 1 MeV/ amu or above. The new technique uses high-energy medium-mass ions, such as Cl, with electronic stopping powers above the threshold value for amorphization ͑5-6 keV/nm͒, reaching the maximum value a few micrometers inside the crystal. At the ultralow fluence regime ͑10 12 -10 13 cm −2 ͒ an effective nanostructured medium is obtained that behaves as an optical waveguide where light propagates transversally to the amorphous nanotracks created by every single impact. The method implies a reduction of 4 orders of magnitude with respect to He implantation. The optical waveguides present reasonable losses ͑ϳ10 dB/ cm͒ and significant secondharmonic generation (SHG) and electro-optic (EO) responses (Ͼ50% bulk) for the lowest fluences. © 2007 Optical Society of America OCIS codes: 130.3730, 130.4310, 160.3730, 190.4390. Ion implantation [1] of light ions (H, He) at energies of 1 -3 MeV is a well-known procedure to fabricate optical waveguides and integrated optics devices on dielectric crystals [2]. The physical basis is the disorder and partial or full amorphization of the crystal at the end of the ion range caused by nuclear collisions between the incoming ions and the atoms of the material. A main disadvantage is that the required ion fluence (and therefore irradiation time) to achieve amorphization is very high ͑10 16 -10 17 cm −2 ͒. This feature has hindered the routine commercial use of ion implantation, so cheaper and simpler methods such as metal in-diffusion [3,4] or proton-exchange [5,6] are mostly used for LiNbO 3 . This crystal has been used in the present work since it is still a reference material in photonics for electro-optic (EO) and nonlinear optical applications [7]. Recently, the use of heavier ions and higher energies to induce damage and amorphization via electronic excitations has started to be explored. A method to produce high index-jump optical waveguides producing thick buried amorphous layers by accumulation of (subthreshold) electronic damage with moderate fluences ͑ϳ10 14 cm −2 ͒ was demonstrated in LiNbO 3 [8] and KGW [9] and is an alternative to light ion implantation.The purpose of this Letter is to go a step further and report on a novel method to fabricate a nanostructured effective medium for LiNbO 3 that acts as an optical waveguide. It dramatically reduces the required ion fluences down to ϳ10 12 cm −2 , while essentially keeping the nonlinear optical performance. The physical basis is as follows: Irradiation with mediummass ions having sufficiently high energy so that their electronic stopping power ͑S e ͒ is above a certain threshold value (S th Ϸ 5 -6 keV/ nm for LiNbO 3 ) generates amorphous tracks with a nanometric diameter [10][11][12][13]. Each track is associated with a single ion impact and presents [12,13] an isotropic refractive index (n a = 2.10 at = 633 nm). It has been show...

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Nonlinear optical waveguides generated in lithium niobate by swift-ion irradiation at ultralow fluences

et al. 2007

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“…Evidence for this structure has been provided by transmission electron microscopy 29 ͑TEM͒ and optical methods. 11 The track core has a nanometer-size diameter D I =2R at the surface and extends a certain length H I into the crystal, which may reach several microns. Both of these magnitudes increase with stopping power S e .…”

Section: A Single Impact Experiments "Low Fluences…: Thresholdingmentioning

confidence: 99%

“…7,[10][11][12][13] In such electronic regime, individual ions generate amorphous ͑latent͒ tracks of only a few nanometers in diameter [14][15][16] when the electronic stopping power overcomes a certain threshold value, which depends on material and, at a lesser extent, on irradiation conditions. This technique opens new possibilities for nanostructuring of materials and may compete with femtosecond-laser pulse irradiation.…”

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“…Therefore, the purpose of this work is to present experimental observations of a number of relevant phenomenological features and explore whether a correlation between laser and ion damage can be reasonably established. We will specifically focus on a relevant photonic material, 18 LiNbO 3 ͑having a gap of around 4 eV͒, where some systematic information on the effect of femtosecond laser [19][20][21][22] and swift-ion irradiation [7][8][9][10][11][12][13][23][24][25] ready available. To the best of our knowledge, only a few systematic comparisons have so far been reported.…”

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Femtosecond laser and swift-ion damage in lithium niobate: A comparative analysis

García-Navarro

Agulló‐López

Olivares

et al. 2008

Journal of Applied Physics

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A first principles study of the lattice stability of diamond-structure semiconductors under intense laser irradiation J. Appl. Phys. 113, 023301 (2013) High-order sideband generation in bulk GaAs Appl. Phys. Lett. 102, 012104 (2013) Defect mediated reversible ferromagnetism in Co and Mn doped zinc oxide epitaxial films J. Appl. Phys. 112, 113917 (2012) Time-domain sampling of x-ray pulses using an ultrafast sample response Appl. Phys. Lett. 101, 243106 (2012) The effects of vacuum ultraviolet radiation on low-k dielectric films App. Phys. Rev. 2012Rev. , 12 (2012 Additional information on J. Appl. Phys. Relevant damage features associated with femtosecond pulse laser and swift-ion irradiations on LiNbO 3 crystals are comparatively discussed. Experiments described in this paper include irradiations with repetitive femtosecond-laser pulses ͑800 nm, 130 fs͒ and irradiation with O, F, Si, and Cl ions at energies in the range of 0.2-1 MeV/amu where electronic stopping power is dominant. Data are semiquantitatively discussed by using a two-step phenomenological scheme. The first step corresponds to massive electronic excitation either by photons ͑primarily three-photon absorption͒ or ions ͑via ion-electron collisions͒ leading to a dense electron-hole plasma. The second step involves the relaxation of the stored excitation energy causing bond breaking and defect generation. It is described at a phenomenological level within a unified thermal spike scheme previously developed to account for damage by swift ions. A key common feature for the two irradiation sources is a well-defined intrinsic threshold in the deposited energy density U th required to initiate observable damage in a pristine crystal: U th Ϸ 1.3ϫ 10 4 −2ϫ 10 4 J / cm 3 for amorphization in the case of ions and U th Ϸ 7 ϫ 10 4 J / cm 3 for ablation in the case of laser pulses. The morphology of the heavily damaged regions ͑ion-induced tracks and laser-induced craters͒ generated above threshold and its evolution with the deposited energy are also comparatively discussed. The data show that damage in both types of experiments is cumulative and increases on successive irradiations. As a consequence, a certain incubation energy density has to be delivered either by the ions or laser photons in order to start observable damage under subthreshold conditions. The parallelism between the effects of laser pulses and ion impacts is well appreciated when they are described in terms of the ratio between the deposited energy density and the corresponding threshold value.

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Recrystallization of amorphous nanotracks and uniform layers generated by swift-ion-beam irradiation in lithium niobate

et al. 2011

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The thermal annealing of amorphous tracks of nanometer-size diameter generated in lithium niobate (LiNbOs) by Bromine ions at 45 MeV, i.e., in the electronic stopping regime, has been investigated by RBS/C spectrometry in the temperature range from 250°C to 350°C. Relatively low fluences have been used (<10 12 cm -2 ) to produce isolated tracks. However, the possible effect of track overlapping has been investigated by varying the fluence between 3 x 10 11 cm -2 and 10 12 cm -2 . The annealing process follows a two-step kinetics. In a first stage (I) the track radius decreases linearly with the annealing time. It obeys an Arrhenius-type dependence on annealing temperature with activation energy around 1.5 eV. The second stage (II) operates after the track radius has decreased down to around 2.5 nm and shows a much lower radial velocity. The data for stage I appear consistent with a solid-phase epitaxial process that yields a constant recrystallization rate at the amorphouscrystalline boundary. HRTEM has been used to monitor the existence and the size of the annealed isolated tracks in the second stage. On the other hand, the thermal annealing of homogeneous (buried) amorphous layers has been investigated within the same temperature range, on samples irradiated with Fluorine at 20 MeV and fluences of ~10 14 cm -2 . Optical techniques are very suitable for this case and have been used to monitor the recrystallization of the layers. The annealing process induces a displacement of the crystallineamorphous boundary that is also linear with annealing time, and the recrystallization rates are consistent with those measured for tracks. The comparison of these data with those previously obtained for the heavily damaged (amorphous) layers produced by elastic nuclear collisions is summarily discussed.

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Optical determination of three-dimensional nanotrack profiles generated by single swift-heavy ion impacts in lithium niobate

Cited by 29 publications

References 18 publications

Nonlinear optical waveguides generated in lithium niobate by swift-ion irradiation at ultralow fluences

Nonlinear optical waveguides generated in lithium niobate by swift-ion irradiation at ultralow fluences

Femtosecond laser and swift-ion damage in lithium niobate: A comparative analysis

Recrystallization of amorphous nanotracks and uniform layers generated by swift-ion-beam irradiation in lithium niobate

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