Towards visible-wavelength passively mode-locked lasers in all-fibre format

锁模皮秒/飞秒光纤激光器具有小型化、光束质量好、稳定性佳、低成本且免维护等优点，然而，目前被动锁模光纤激光器工作波段仍主要局限在近红外1-2 μm光谱区域，在可见光波段（380-760 nm）却几乎未有进展。如何实现可见光被动锁模光纤激光器，直接产生小型化、低成本且高性能的可见光超快激光，是一直困扰超快激光研究领域的一个难题。罗正钱教授课题组通过数值求解金兹伯格-朗道方程，发现耗散孤子谐振机制利于可见光波段超大色散光纤腔被动锁模脉冲的稳定建立。基于数值模拟的结果，该研究成果是在可见光范围内向小型化超快光纤激光器迈出的重要一步。将为可见光超快光纤激光在精密光谱学、生物医学、显微成像、光通信、科学研究等领域的应用奠定基础，具有很好的研究潜力和应用价值。厦门大学为该论文的第一署名单位，电子科学与技术学院博士研究生邹金海为论文第一作者，罗正钱教授为论文通讯作者。Mode-locked fibre lasers (MLFLs) are fundamental building blocks of many photonic systems used in industrial, scientific and biomedical applications. To date, 1–2 μm MLFLs have been well developed; however, passively mode-locked fibre lasers in the visible region (380–760 nm) have never been reported. Here, we address this challenge by demonstrating an all-fibre visible-wavelength passively mode-locked picosecond laser at 635 nm. The 635 nm mode-locked laser with an all-fibre figure-eight cavity uses a Pr/Yb codoped ZBLAN fibre as the visible gain medium and a nonlinear amplifying loop mirror as the mode-locking element. First, we theoretically predict and analyse the formation and evolution of 635 nm mode-locked pulses in the dissipative soliton resonance (DSR) regime by solving the Ginzburg-Landau equation. Then, we experimentally demonstrate the stable generation of 635 nm DSR mode-locked pulses with a pulse duration as short as ~96 ps, a radio-frequency signal-to-noise ratio of 67 dB and a narrow spectral bandwidth of 1 nm) and modulated optical spectrum. This work represents an important step towards miniaturized ultrafast fibre lasers in the visible spectral region.This work was supported by the Major Research Plan of the National Natural Science Foundation of China (91750115), Equipment Pre-research Project of Equipment Development Department of Central Military Commission (61404140112), and Natural Science Foundation of Fujian Province for Distinguished Young Scientists (2017J06016).Prof. Zhengqian Luo acknowledges the Program for Young Top Notch Talents of Fujian Province and the Program for Nanqiang Young Top Notch Talents of Xiamen University.该研究受到国家自然科学基金、福建省杰出青年基金、福建省特支‘双百’青年拔尖人才项目以及厦门大学南强青年拔尖人才项目的支持

Silicon Layer Intercalation of Centimeter-Scale, Epitaxially-Grown Monolayer Graphene on Ru(0001)

We develop a strategy for graphene growth on Ru(0001) followed by silicon-layer intercalation that not only weakens the interaction of graphene with the metal substrate but also retains its superlative properties. This G/Si/Ru architecture, produced by silicon-layer intercalation approach (SIA), was characterized by scanning tunneling microscopy/spectroscopy and angle resolved electron photoemission spectroscopy. These experiments show high structural and electronic qualities of this new composite. The SIA allows for an atomic control of the distance between the graphene and the metal substrate that can be used as a top gate. Our results show potential for the next generation of graphene-based materials with tailored properties.Comment: 13 pages, 4 figures, to be published in Appl. Phys. Let

A Study On Gold Nanoparticle Synthesis Using Oleylamine As Both Reducing Agent And Protecting Ligand

The growth kinetics and mechanism of a gold nanoparticle synthesis using water as a single phase solvent and oleylamine as both reducing agent and monolayer protection agent were studied. FT-IR and 1H NMR spectroscopic analysis revealed a conversion of oleylamine ligands to oleylamides when gold(III) was reduced to gold(I) and gold atoms. During the reaction, it was found by UV-Vis absorption spectroscopy and transmission electron microscopic study that oleylamine ligands formed large complex aggregates with gold salt instantly upon mixing these two agents together. At an elevated temperature of 80°C, the complex decomposed first into very small particles and then the small particles recombined together into larger and thermally stable particles with an average core size around 9-10 nm. The oleylamide ligands formed a protecting monolayer around the nanoparticles through a hydrogen bonding network between the amide groups. The recombination of small particles into larger ones was found to follow a logistic model, as confirmed by a nonlinear regression fitting of the UV-Vis absorption data of the reaction solution with the mathematical model. Copyright © 2007 American Scientific Publishers All rights reserved

Solid Phase Monofunctionalization Of Gold Nanoparticles Using Ionic Exchange Resin As Polymer Support

A solid phase modification method using anionic exchange resin as polymer support was developed for the synthesis of monofunctional gold nanoparticles. Based on a catch and release mechanism to control the number of functional groups attached to the nanoparticle surface, bifunctional thiol ligands with a carboxylic acid end group were first immobilized at a controlled density on anionic exchange resin through electrostatic interactions. Gold nanoparticles were then immobilized to the anionic exchange resin by a one-to-one place exchange reaction between resin-bound thiol ligands and butanethiol-protected gold nanoparticles in solution. After cleaving off from the resin under mild conditions, gold nanoparticles with a single carboxyl group attached to the surface were obtained as the major product. Experimental conditions such as the solvents used for ligand loading and solid phase place exchange reaction, and the loading density of the ligands, were found to play a critical role towards the successful synthesis of monofunctional nanoparticles. Overall, the noncovalent bond-based ligand immobilization technique reported here greatly simplified the process of solid phase monofunctionalization of nanoparticles compared to a previously reported covalent bondbased ligand immobilization technique. Copyright © 2007 American Scientific Publishers All rights reserved

Direct Laser Writing Of Microtunnels And Reservoirs On Nanocomposite Materials

A direct laser writing technique has been developed to create microtunnels and reservoirs on a nanocomposite material by utilizing the photon-thermal energy conversion property of gold nanoparticles. The absorption of photon energy and conversion to thermal energy by gold nanoparticles embedded in a polymer matrix caused polymer decomposition at the subsurface layer of the nanocomposite film, leading to the formation of covered microtunnels. Laser ablation/writing of polymer and doped-polymer materials has been widely used for the fabrication of microfluidic channels, optical devices and microelectromechanical systems (MEMS). Dye molecules with a strong absorption at certain wavelength ranges are often added to the polymers as photon-thermal energy converters to extend the range of polymers that may be processed by laser irradiation

Monofunctional Gold Nanoparticles Prepared Via A Noncovalent-Interaction-Based Solid-Phase Modification Approach

The solid-phase preparation of monofunctionalized gold nanoparticles using noncovalent interaction was presented. The solid support used in this preparation was amino-group functionalized silica gel. The bifunctional ligands, 11-mercaptoundecanoic acid (MUA), were then loaded onto the support directly as a result of the electrostatic interaction of the positively charged amino groups from the silica gel with the negatively charged carboxylic acid groups from the MUA ligands. The nanoparticle was purified by washing with petroleum ether, followed by gel permeation chromatography to give 60-90 % yield of monocarboxyl gold nanoparticles. In addition to amino-group-functionalized silica gel, Rink resin, an amino-group-functionalized resin consisting of a lightly crosslinked polystyrene matrix, was also used for the surface functionalization of the gold nanoparticles. The most reliable method of determining the relative purity of the monofunctional nanoparticle product is by conducting a dimine-coupling reaction with the solid-phase-modified nanoparticles and using TEM to analyze the coupled product

Monofunctional Gold Nanoparticles Prepared via a Noncovalent‐Interaction‐Based Solid‐Phase Modification Approach

The solid-phase preparation of monofunctionalized gold nanoparticles using noncovalent interaction was presented. The solid support used in this preparation was amino-group functionalized silica gel. The bifunctional ligands, 11-mercaptoundecanoic acid (MUA), were then loaded onto the support directly as a result of the electrostatic interaction of the positively charged amino groups from the silica gel with the negatively charged carboxylic acid groups from the MUA ligands. The nanoparticle was purified by washing with petroleum ether, followed by gel permeation chromatography to give 60-90 % yield of monocarboxyl gold nanoparticles. In addition to amino-group-functionalized silica gel, Rink resin, an amino-group-functionalized resin consisting of a lightly crosslinked polystyrene matrix, was also used for the surface functionalization of the gold nanoparticles. The most reliable method of determining the relative purity of the monofunctional nanoparticle product is by conducting a dimine-coupling reaction with the solid-phase-modified nanoparticles and using TEM to analyze the coupled product

Visible-wavelength pulsed lasers with low-dimensional saturable absorbers

The recent renaissance in pulsed lasers operating in the visible spectral region has been driven by their significant applications in a wide range of fields such as display technology, medicine, microscopy, material processing, and scientific research. Low-dimensional nanomaterials as saturable absorbers are exploited to create strong nonlinear saturable absorption for pulse generation at visible wavelengths due to their absorption peaks located in visible spectral region. Here we provide a detailed overview of visible-wavelength pulsed lasers based on low-dimensional nanomaterials, covering the optical properties and various integration strategies of these nanomaterials saturable absorbers, and their performance from solid-state as well as fiber pulsed lasers in the visible spectral range. This emerging application domain will undoubtedly lead to the rapid development of visible pulsed lasers