1,721,005 research outputs found
Self-organized nanogratings in glass irradiated by ultrashort light pulses
Full text linkPeriodic nanostructures are observed inside silica glass after irradiation by a focused beam of a femtosecond Ti:sapphire laser. Backscattering electron images of the irradiated spot reveal a periodic structure of stripelike regions of ~20 nm width with a low oxygen concentration, which are aligned perpendicular to the laser polarization direction. These are the smallest embedded structures ever created by light. The period of self-organized grating structures can be controlled from ~140 to 320 nm by the pulse energy and the number of irradiated pulses. The phenomenon is interpreted in terms of interference between the incident light field and the electric field of the bulk electron plasma wave, resulting in the periodic modulation of electron plasma concentration and the structural changes in glass
Recent advances in ultrafast laser processing of transparent materials
No full textInteraction of intense ulrashort light pulses with transparent materials reveal new interesting properties and phenomena. Recent demonstrations of 3D nanoripple formation, self-assembled form birefringency and ultrafast laser calligraphy are reviewed
Manipulation of self-assembled nanostructure in glass
No full textWe observed ultrafast writing dynamics of form birefringence produced by self-organized nanogratings. Rewritable five-dimensional optical data storage using self-assembled form birefringence was demonstrated
Self-organized nanostructures in glass irradiated by femtosecond light pulses
No full textThe ability to control light and properties of matter in small space regions and over short time intervals becomes more important as performances of electronic and optical devices are pushed to the limits. In this respect the use of femtosecond lasers to directly write photonic structures deep within transparent media has recently attracted much attention due to its capability for precise microfabrication in three-dimensions. Recent observations of anisotropic light scattering and reflection from the regions modified by intense femtosecond light pulses in the direction parallel to the polarization of wring laser, have given the evidence of sub-wavelength index gratings imprinted in irradiated materials. Form birefringence induced by self-organized sub-wavelength index gratings has been also proposed to explain a puzzling phenomenon of uniaxial birefringence of structures written within silica glass. Recently we reported direct proof of the existence of such gratings. Surface gratings with a period equal to the wavelength of incident light have been observed in many experiments involving laser deposition and laser ablation. The results of our work give the first evidence self-organized structures within the bulk of material. The observed self-organized periodic structures are the smallest (20 nm width) and the strongest (-0.2 index change) ever created by light in transparent materials. Moreover these are the first gratings created by light-matter (electron plasma) interference. In this paper the study of self-organized nanostructures in glasses is reviewed
New phenomena in ultrafast laser micro-processing: from quill to non-reciprocal writing
No full textModification of transparent materials with ultrafast lasers has attracted considerable interest due to a wide range of applications including laser surgery, integrated optics, optical data storage, 3D micro- and nano-structuring [1]. Three different types of material modifications can be induced with ultrafast laser irradiation in the bulk of a transparent material, silica glass in particular: an isotropic refractive index change (type 1); a form birefringence associated with self-assembled nanogratings and negative refractive index change (type 2) [2,3]; and a void (type 3). In fused silica the transition from type 1 to type 2 and finally to type 3 modification is observed with an increase of fluence. Recently, a remarkable phenomenon in ultrafast laser processing of transparent materials has been reported manifesting itself as a change in material modification by reversing the writing direction (Figure 1a) [4]. The phenomenon has been interpreted in terms of anisotropic plasma heating by a tilted front of the ultrashort laser pulse. Moreover a change in structural modification has been demonstrated in glass by controlling the direction of pulse front tilt, achieving a calligraphic style of laser writing which is similar in appearance to that inked with the bygone quill pen [5]. It has also been a common belief that in a homogeneous medium, the photosensitivity and corresponding light-induced material modifications do not change on the reversal of light propagation direction. More recently it have observed that in a non-centrosymmetric medium, modification of the material can be different when light propagates in opposite directions (KaYaSo effect, Figure 1b) [6]. In particular, when the direction of the femtosecond laser beam is reversed from +Z to – Z directions, the structures written in lithium niobate crystal when translating the beam along the +Y and –Y directions are mirrored. This is the first evidence of a new optical phenomenon of non-reciprocal photosensitivity. We interpret this effect in terms of light pressure and associated heat flow resulting in a temperature gradient in homogeneous media without inversion symmetry under uniform intense irradiation. Non-reciprocity is produced by magnetic field (Faraday effect) and movement of the medium with respect to the direction of light propagation: parallel (Sagnac effect) or perpendicular (KaYaSo effect). We anticipate that the observed phenomena will open new opportunities in laser material processing, laser surgery, optical manipulation and data storage
Manipulation of form birefringence in isotropic material
No full textForm-birefringent nanostructure composed of the self-organized oxygen defects can be created by light pulses with a width of 70 fs. Such rewritable and directionally controllable nanostructures have evolved by lowering threshold for defect formation
Nanostructuring of transparent materials by ultrashort light pulses
No full textThe study of the smallest (20 nm width) and the strongest (-0.2 index change) embedded periodic structures ever created by light in transparent materials are reported. These are the first gratings created by light-matter (electron plasma) interference
Optical anisotropy of self-assembled nanostructure in glass
No full textFemtosecond laser direct writing of form birefringence originated from self-organized nanostructure in glass is reviewed. Its application to rewritable five-dimensional optical data storage is also demonstrated
Self-organization in glass by light: From second-order nonlinearity to 3D nano-structures
No full textThe physics and applications of self-organised periodic structures in glass ranging from the second-order nonlinearity gratings produced by intense infrared irradiation to the periodic sub-wavelength structures induced by intense femtosecond light pulses are reviewed
New phenomena in interaction of intense ultrashort light pulses with transparent materials: from 3D self-assembled nanostructures to quill writing and nonreciprocal photosensitivity
No full textInteraction of intense ulrashort light pulses with transparent materials reveal new ultrafast phenomena. Recent demonstrations of 3D nanoripple formation, ultrafast laser calligraphy and nonreciprocal photosensitivity are reviewed
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