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As a promising approach to laser nanoprocessing, much interest has been focused on the self-organized, periodic surface nano structure s that are often observed in the femtosecond (fs) laser ablation experiment [1], while the ultrafast interaction poses a significant challenge to controlling the nanostructuring process and fabricating well-defined nano structures. Here we demonstrate that surface...
Direct laser writing is a versatile technique for the fabrication of three-dimensional nano- and microstructures and has become recently commercially available [1]. Lateral feature sizes down to 100 nm are routinely achieved due to two-photon absorption and the threshold behaviour of the photoresists. The finite numerical aperture of the objective lens used in most systems (typically NA 1.4, oil immersion)...
In the past few decades, 3D direct writing with focused femtosecond laser pulses has emerged as a technique for microfabrication inside transparent dielectrics like fused silica. It has been demonstrated that the control and the confinement of the non-linear interaction can lead to a wide variety of modifications: from a small uniform change of the refractive index to structural modifications opening...
Asymmetric GaN planar waveguides grown on (0001) sapphire by molecular beam epitaxy are promissing submicro-metric periodically poled (PP) structures required for quasi-phase-matching the counterpropagatingthree-wave parametric interactions [1, 2]. However, the realization of cm long waveguides presenting a submicronic periodicity is not possible without moving the sample under the writing beam. This...
Fiber lasers with fiber-Bragg gratings (FBGs) inscribed directly into the active fiber improve the laser lifetime as the laser resonator is fully integrated and there are no splices between the two FBGs which could generate a failure [1]. Such monolithic fiber lasers can find variety of applications, e.g., in high-power sources, narrow-bandwidth short-cavity sources for spectral-beam combining, compact...
Optical ultrashort pulses are used in wide application areas, such as a light source for millimeter/terahertz wave sources for high-speed wireless communication systems, optical sampling technologies, and so forth. For these applications, ultrashort pulse sources are required to have compactness, high stability, low timing jitter, and tunability in both wavelength and repetition rate for high accuracy...
Mode instabilities, which have recently been reported in many high-power fiber laser systems, are currently appointed as one of the most limiting factors for power scaling of fiber lasers and amplifiers [1]. They origin from the thermo-optic effect, which causes an increase of the refractive index linearly dependent upon the temperature, which allows propagation of one or more High-Order Modes (HOMs)...
Most of the tunable Yb-doped fiber lasers exploit the quasi-four-level system between 1030–1100 nm [1-2]. Extending the tunability over the whole emission bandwidth of Yb-glass and therefore covering the wavelengths between 976 nm and 1020 nm requires (i) reaching transparency and (ii) controlling the gain competition between short wavelengths (three-level transition) and 1030 nm emission (quasi three-level...
Lasers with random distributed feedback (DFB) owing to Rayleigh scattering in optical fibers [1] have attracted a great interest: a number of papers demonstrating new laser schemes and applications have been proposed [2-7] recently. Moreover, the generation output power and, more generally, generation power distribution could be described both analytically and numerically within simple balance models...
Rare-earth doped fiber lasers have emerged as attractive alternatives to traditional lasers in material processing due to the ruggedness, high efficiencies, and excellent beam quality [1]. The development of pulsed fiber lasers is driven by the fact that specific applications require different peak powers, repetition rates, and pulse energies. Some of the methods of pulsing the lasers completely avoid...
Optical Cherenkov radiation (OCR) is referred to as dispersive wave (DW) generation or non-solitonic radiation originating from soliton propagation perturbed by high order dispersion (HOD). The OCR becomes of particular importance for octave-spanning spectral broadening and blue-shifted supercontinuum generation (SCG) [1]. When the OCR generation lies in the anomalous GVD region and tends to be a...
Wavelengths around 1480 nm can be used to pump Er-doped systems [1] in order to overcome small efficiencies and huge heat loads typically related with pumping wavelengths in the 976 nm region. Additionally, Er-doped fibers suffer from fundamental limits in doping concentration, so that pump sources with high brightness to enable core pumping are preferred over multimode (976nm or 1480nm) laser diodes...
Neodymium-doped yttrium aluminum garnet (Nd:YAG) crystals are one of the favorite gain media for solidstate lasers owing to their outstanding fluorescence, thermal and mechanical properties. In this material planar and channel waveguides have been realized recently using ion beam irradiation or fs laser inscription [1,2]. Here we report on fabrication of ridge waveguides in a Nd:YAG crystal by using...
The photodarkening (PD) loss appears as time dependent broadband loss with peak at visible wavelengths and a long tail extending to near infrared wavelengths. The origin of PD is still under debate but in [1] it is proposed to be due to a “1½” bond color center (CC). The mechanism for CC absorption is by photon electric field excitation to the ionic three electron bond (TEB) of =Si<O2 :· Yb inducing...
Random distributed feedback (DFB) fiber lasers have attracted a great attention since first demonstration [1]. Despite big advance in practical laser systems, random DFB fiber laser spectral properties are far away to be understood or even numerically modelled. Up to date, only generation power could be calculated and optimized numerically [1,2] or analytically [3] within the power balance model....
Due to their features of high output power and broad wavelength band, Ytterbium-doped (Yb) fiber lasers have been investigated and developed for wide applications in the industrial, chemical, and biomedical markets [1]. Femtoseconds and picoseconds Mode-locked Yb fiber lasers have cast lots of attention and interests for various nonlinear spectroscopic and imaging systems [1-3]. Tunability of wavelength...
In the over 100 years since Wood first observed that gratings can resonantly couple light to guided modes -in this case surface plasmon polaritons (SPPs) on a metal film [1] - this process has been extensively studied, modeled, and is now used in countless plasmonic and photonic devices. At the heart of grating mediated resonant coupling lies the phenomenon of interference: coherent scattering from...
In contrast to ordinary materials, optical metamaterials can interact with light in unprecedented ways, enabling novel applications in, e.g., subwavelength imaging and optical cloaking. These extraordinary properties all originate from the excitation of higher-order multipoles in the building blocks constituting the metamaterial. Unfortunately, the knowledge of how to extract the contribution of higher-order...
A long chase for the elusive dynamic toroidal moments has been recently concluded by detecting a spectral signature of the toroidal dipolar resonance in the response of a specially designed electromagnetic metamaterial [1]. This observation brings up a new interest to the prediction made by Afanasiev and Stepanovsky in 1994 that a combination of oscillating toroidal and conventional electric dipoles...
We present our research into the fabrication of fully three-dimensional metallic nanostructures using Diffusion-Assisted Direct Laser Writing, a technique that employs quencher diffusion for the fabrication of 3D structures with resolution beyond the diffraction limit [1]. The fabrication is done by firstly making dielectric structures inside a hard polymer network containing metal-binding groups,...
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