Multi-wavelength distributed feedback laser array based tunable semiconductor lasers have been widely used owing to their high mode stability and simple tuning scheme. Comparing with the in-parallel ...laser array, the in-series one can avoid a large power loss caused by the optical combiner. However, the single-mode stability of an in-series laser array is vulnerable to the reflections of other lasers. Here we experimentally demonstrated a tunable in-series laser array with high single-mode stability and high uniformity of wavelength spacing. To reduce the impact of such reflections, the Bragg gratings in different lasers were designed in phase, and the grating phase error was reduced by utilizing the reconstruction-equivalent-chirp technique. Besides, a three-section laser structure was applied in each laser to increase the priority of the dominant lasing mode. Four lasers with small wavelength-spacings of 2.5 nm were integrated in the in-series laser array. According to the measurement results of 40 in-series laser arrays (160 lasers), wavelength deviations of 90.6% lasers were within ±0.2 nm, average wavelength spacings of 97.5% of the measured laser arrays were deviated from the design within ±0.2 nm, and SMSRs of 96.3% lasers were above 45 dB. The output power was above 25 mW and the relative intensity noise was below −130 dB/Hz. Like the in-parallel laser array, the proposed laser array can be applied in either continuous wavelength tuning or fast channel switching. For the continuous wavelength tuning applications, the 10-nm tuning range was obtained with a temperature tuning range of less than 20 °C. For the fast channel switching applications, four channels with 2.5-nm spacing are available, and the switching time between two channels was less than 300 ns.
Nanomaterials are a large area of research at present. These materials, which have at least one of their dimensions in the nanoscale (i.e., in a length range from 1 nm to 100 nm), have remarkable or ...unconventional properties, unlike bulk materials. These materials are currently used in many applications; however, new potential uses are being investigated. In this sense, there is large interest in their use in medicine, electronic devices, the production and storage of energy, composite materials, etc. The production of nanomaterials is addressed through physical and/or chemical methods; however, most of these methods exhibit low reproducibility or a low production rate or make use of toxic chemicals. In order to avoid most of these drawbacks, the laser-based synthesis of nanomaterials has emerged as an alternative to overcome these limitations. This family of methods use a laser beam to produce different nanomaterials (e.g., nanoparticles, nanowires or 2D materials) using diverse approaches. Techniques such as those based on laser ablation, laser vaporization, pulsed laser deposition (PLD), laser–chemical vapor deposition (LCVD), etc., are being explored at present to fabricate these nanoscale materials with a controlled size and shape. In this context, here we present research papers addressing the most recent developments in this field to summarize the current state of the art in the synthesis of nanomaterials using laser techniques.
Femtosecond laser micromachining of transparent material is a powerful and versatile technology. In fact, it can be applied to several materials. It is a maskless technology that allows rapid device ...prototyping, has intrinsic three-dimensional capabilities and can produce both photonic and microfluidic devices. For these reasons it is ideally suited for the fabrication of complex microsystems with unprecedented functionalities. The book is mainly focused on micromachining of transparent materials which, due to the nonlinear absorption mechanism of ultrashort pulses, allows unique three-dimensional capabilities and can be exploited for the fabrication of complex microsystems with unprecedented functionalities.This book presents an overview of the state of the art of this rapidly emerging topic with contributions from leading experts in the field, ranging from principles of nonlinear material modification to fabrication techniques and applications to photonics and optofluidics. Roberto Osellame is a Research Associate at the Institute of Photonics and Nanotechnology (IFN), Milan, Italy, of the National Research Council (CNR). From 2001 he is also a Contract Professor of Experimental Physics at the Politecnico di Milano. His research interests include integrated all-optical devices on nonlinear crystals, femtosecond laser micromachining of transparent material, fabrication and characterization of photonic and optofluidic devices and biophotonic applications. He is author of more than 60 scientific papers in premier peer-reviewed journals and received several invitations to major international conferences. He is inventor of two licensed patents in the field of photonics. He is in the technical program committees of the conferences CLEO Europe and Photonics West. He is currently the project coordinator of the 7th Framework Program EU project 'microFLUID' (2008-2011). Giulio Cerullo is Associate Professor of Physics at Politecnico di Milano. His current scientific interests concern generation of few-optical-cycle pulses, ultrafast spectroscopy with time resolution down to a few femtoseconds, and micro/nanostructuring by ultrashort pulses. He is the author of about 200 papers in international journals and has given over 40 invited presentations at international conferences. He is in the technical program committees of the conferences CLEO Europe, CLEO U.S.A., Photonics Europe and Ultrafast Phenomena. He is Topical Editor of the journal Optics Letters for the topic Ultrafast Optical Phenomena. He coordinates the European project HIBISCUS (Hybrid Integrated Bio-Sensors Created by Ultrafast Laser Sources). Roberta Ramponi is Full Professor of Physics at the Politecnico di Milano, and chair of the bachelor and master-of-science degrees in Physics Engineering. She has a long-standing cooperation with the CNR Institute of Photonics and Nanotechnology as associate researcher. Her research activity includes integrated and nonlinear optics, the development of novel fabrication and characterization techniques for optical waveguides, and photonic devices for applications to telecommunications and to biomedical and environmental sensing. She is co-author of over 130 international publications. She was the President of the European Optical Society (EOS) in 2006-2008, now being the Past-President.
This reprint is the printed edition of the Special Issue published in Materials. The reprint provides an overview on current international research activities in the field of advanced pulse laser ...machining technology. It covers fundamental and applied aspects and collects contributions of renowned scientists from academics and industries working in the fields of laser processing, materials science, physics, chemistry, and engineering in order to foster the current knowledge and present new ideas for future applications and new technologies.
We report here a wavelength widely step-tunable nanosecond 4 μm fiber laser based on HBr-filled hollow-core fibers (HCFs), which is pumped by an acousto-optic modulated narrow linewidth 2 μm ...thulium-doped fiber amplifier (TDFA) seeded by several thermally tunable diode lasers. The modulated pump pulses excite the first overtone transition of the HBr molecules in HCFs with single-pass configuration, resulting in a number of mid-infrared laser emissions containing both P and R branch fundamental transition lines from 3.87 μm to 4.5 μm. To the best of our knowledge, this is the first tunable pulsed mid-infrared fiber laser beyond 3.8 μm, and it is also the largest tuning range achieved to date for any pulsed fiber laser not by nonlinear effects. The maximum average power of 550 mW associated with a single pulse energy of 0.37 μJ (pulse duration 20 ns, pulse repetition rate 1.5 MHz) is achieved at 4.17 μm, and the laser slope efficiency is about 15.6%. The mid-infrared laser shows a good fundamental mode with a measured beam quality factor M 2 of about 1.15. The time and frequency domain characteristics are also experimentally investigated in detail. The versatility of such gas-filled HCF laser offers much flexibility in selected molecule gain media and HCF species for power scaling and wavelength extending of pulsed mid-infrared fiber lasers.
A detailed analysis of theexcited state absorption (ESA) transition 4 I 13/2 → 4 I 9/2 which occurs in erbium (Er) doped ZBLAN fiber lasers is performed through numerical modeling. It is found that ...the ESA plays a significant role in enhancing the 2.8 μ m lasing of Er 3+ ions. The ESA promotes the ions residing in 4 I 13/2 (the lower state of the 2.8 μ m laser) to 4 I 9/2 , where the ions subsequently decay to 4 I 11/2 (the upper state of the 2.8 μ m laser) rapidly. An energy recycling is consequently realized via the ESA. The ESA can be activated in cascaded 2.8 μ m/1.6 μ m Er-doped ZBLAN fiber lasers by absorbing the 1.6 μ m signal. Through numerical simulation it is found that in cascaded lasers the slope efficiency of the 2.8 μ m laser can be elevated to ∼48% with the assistance of the ESA, a value that surpasses the Stokes limit (∼35%) substantially and agrees well with the experimental results previously reported. It is also found that the ESA-induced energy recycling is exothermic, an effect that is non-ignorable in the high-power circumstance. Moreover, the injection of an additional 1.6 μ m pump for directly exploiting the 4 I 13/2 → 4 I 9/2 ESA is simulated using the model. It is found that as the second pump is introduced, the 2.8 μ m lasing almost entirely relies on the ESA-induced energy recycling, and hence, the laser is capable of operating under very low 976 nm pump power. The simulation results indicate that the 2.8 μ m lasing in Er-doped ZBLAN fiber lasers can even be realized using a single 1.6 μ m pump, via a combination of the 4 I 15/2 → 4 I 13/2 and 4 I 13/2 → 4 I 9/2 transition. The outcomes of this work can inspire the development of novel, high-performance 2.8 μ m Er-doped ZBLAN fiber lasers.
This volume presents the latest advancements and future perspectives of atomic, molecular and optical (AMO) physics and its vital role in modern sciences and technologies. The chapters are devoted to ...a wide range of quantum systems, with an emphasis on the understanding of ionization, high-harmonic generation, molecular orbital imaging and coherent control phenomena originating from light-matter interactions. The book overviews current research landscape and highlight major scientific trends in AMO physics interfacing with interdisciplinary sciences. It may be particularly interesting for young researchers working on establishing their scientific interests and goals.Contents:Long Range Ionic Potential Effect on Strong-Field Tunneling (Xufei Sun, Min Li, Chengyin Wu, and Yunquan Liu)Photoelectron Interference and Photoelectron Holography (Min Li, Qihuang Gong, and Yunquan Liu)Dissociation of Hydrogen Molecular Ions in Strong Laser Fields (Feng He)Nonsequential Double Ionization of Atoms in Strong Laser Field (Difa Ye, Libin Fu, and Jie Liu)Few-Photon Double Ionization of He and H2 (Wei-Chao Jiang, Wei-Hao Xiong, Ji-Wei Geng, Qihuang Gong, and Liang-You Peng)Probing Orbital Symmetry of Molecules Via Alignment-Dependent Ionization Probability and High-Order Harmonic Generation by Intense Lasers (Song-Feng Zhao, Xiao-Xin Zhou, and C D Lin)High-order Harmonic Generation Driven by Sub-Cycle Shaped Laser Field (Yinghui Zheng, Zhinan Zeng, Pengfei Wei, Jing Miao, Ruxin Li, and Zhizhan Xu)Imaging Ultra-fast Molecular Dynamics in Free Electron Laser Field (Y Z Zhang and Y H Jiang)Readership: This book is most suitable for the active scientists and graduates in strong-field community and also for other scientists who work with the ultrafast lasers in biology and chemistry. Key Features:Contributors for this volume are all internationally recognized experts in their fieldsThe book offers a unique overview of the state of current AMO physics, while outlining future directions. No comparable titles were identified so far (by editors or by reviewers)All contributions include new unpublished research, and will be of interest for anyone pursuing scientific investigations in presented areas
Recent progress in chromium and iron doped II‐VI semiconductor materials makes them the laser sources of choice when one needs a compact system with tunability over 1.9–5.1 μm. Output powers ...exceeding 10 W and efficiency up to 70% were demonstrated in several Cr doped semiconductors. The unique combination of technological (low‐cost ceramic material) and spectroscopic characteristics makes these materials ideal candidates for mid‐IR tunable laser systems. This article reviews transition metal doped II–VI materials and recent progress in Cr‐ and Fe‐doped solid‐state mid‐IR lasers.
Recent progress in chromium‐ and iron‐doped II‐VI semiconductor materials makes them the laser sources of choice when one needs a compact system with tunability over 1.9–5.1 µm. Output powers exceeding 10 W and efficiencies up to 70% were demonstrated in several Cr‐doped semiconductors. The unique combination of technological (low‐cost ceramic material) and spectroscopic characteristics makes these materials ideal candidates for mid‐IR tunable laser systems. This article reviews transition‐metal‐doped II‐VI materials and recent progress in Cr‐ and Fe‐doped solid‐state mid‐IR lasers.
Particle accelerators and radiation based on radio-frequency (RF) cavities have significantly contributed to the advancement of science and technology in the most recent century. However, the rising ...costs and scales for building cutting-edge accelerators act as barriers to accessing these particle and radiation sources. Since the introduction of chirped pulse amplification technology in the 1990s, short-pulse, high-power lasers have enabled the realization of laser-driven accelerations and radiation sources. Laser-driven accelerators and radiation sources could be a viable alternative to providing compact and cost-effective particle and photon sources. An accelerating field in a plasma, driven by intense laser pulses, is typically several orders of magnitude greater than that of RF accelerators, while controlling the plasma media and intense laser pulses is highly demanding. Therefore, numerous efforts have been directed toward developing laser-driven high-quality particle beams and radiation sources with the goal of paving the way for these novel sources to be used in a variety of applications. This Special Issue covers the latest developments in laser-based ion and electron accelerators; laser-plasma radiation sources; advanced targetry and diagnostic systems for laser-driven particle accelerators; particle beam transport solutions for multidisciplinary applications; ionizing radiation dose map determination; and new approaches to laser–plasma nuclear fusion using high-intensity, short laser pulses.
