High-harmonic generation is one of the most extreme nonlinear-optical processes observed to date. By focusing an intense laser pulse into a gas, the light-atom interaction that occurs during the process of ionising the atoms results in the generation of harmonics of the driving laser frequency, that extend up to order  300 (corresponding to photon energies from 4 to >500eV). Because this technique is simple to implement and generates coherent, laser-like, soft-x-ray beams, it is currently being developed for applications in science and technology including probing of dynamics in chemical and materials systems and for imaging. In this work we demonstrate that by carefully controlling the shape of intense light pulses of 6-8 optical cycles, we can control the interaction of light with an atom as it is being ionised, in a way that improves the efficiency of x-ray generation by an order of magnitude. Furthermore, we demonstrate that it is possible to control the spectral characteristics of the emitted radiation and to channel the interaction between different- order nonlinear processes. The result is an increased utility of harmonic generation as a light source, as well as the first demonstration of optical pulse-shaping techniques to control high-order nonlinear processes.

We present a multi- octave, mid-infrared supercontinuum source spanning from 3.6 mu m and extending into long-wave infrared region out to 11 mu m with an exceptionally high conversion efficiency of 8.2% and output power of 39 mW. These results were enabled by intra-pulse difference frequency generation involving a femtosecond Thulium doped fiber laser, an indium fluoride fiber and a zinc germanium phosphide crystal.

We present a femtosecond-pumped, octave-spanning, FTIR-compatible supercontinu-um covering 5-11 μm. The SC is generated with record efficiency in ZGP through intra-pulse DFG of a spectrally broaden fiber laser with a 15-fs pulse centered around 2-μm.

Utilizing highly cascaded harmonic generation, we upconvert a MHz fiber laser to the vacuum ultraviolet (up to 18 eV). We apply the source to combustion-chemistry experiments and conduct numerical simulation to understand the nonlinear generation process.

Vacuum ultraviolet (VUV) light is critical for the study of molecules and materials, but the generation of femtosecond pulses in the VUV region at high repetition rates has proven difficult. Here, we demonstrate the efficient generation of VUV light at MHz repetition rates using highly cascaded four-wave mixing processes in a negative-curvature hollow-core fiber. Both even and odd order harmonics are generated up to the 15th harmonic (69 nm, 18.0 eV), with high energy resolution of ~40 meV. In contrast to direct high harmonic generation, this highly cascaded harmonic generation process requires lower peak intensity and therefore can operate at higher repetition rates, driven by a robust ~10 W fiber-laser system in a compact setup. Additionally, we present numerical simulations that explore the fundamental capabilities and spatiotemporal dynamics of highly cascaded harmonic generation. This VUV source can enhance the capabilities of spectroscopies of molecular and quantum materials, such as photoionization mass spectrometry and time , angle , and spin-resolved photoemission.

Using a cascaded four-wave-mixing process in negative-curvature fibers, we produce high-flux, high-rep-rate femtosecond pulses of UV and VUV light with wavelengths as short as 115 nm, with applications in spectroscopy and materials science.

W ELCOME to the IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS (JSTQE) Issue on Ultrafast Science & Technology. The field has seen a big highlight, since the Nobel prize in physics for 2018 was announced in high intensity lasers. The application space integrates state-of-the-art photonics techniques coming from the areas of quantum electronics, lasers, fiber optics and electro-optics to chemistry. This field continues to vastly expand with advanced developments across the entire spectrum of ultrafast applications ranging from fundamental laboratory studies to high harmonic generation, attosecond science, non-linear optics, and laser innovation. Recently developed innovative technologies have made a significant impact on ultrafast research in many areas, and is now expanding out of the realm of fundamental science research to industrial applications. In the papers included in this JSTQE Issue on UST, you will be introduced to some of the latest leading-edge developments in generating, propagating, measuring, and applications of ultrafast pulses of light. Moreover, the UST field has introduced opportunities for interdisciplinary research between physicists, chemists and engineers leading to the development of novel laser, fiber optics, and high intensity light in the midInfrared, to EUV region of the electromagnetic spectrum, which is employed in a broad range of scientific areas. The objective of this JSTQE Issue on Ultrafast Science and Technology is to highlight recent progress, challenges and trends in innovative UST developments. The papers published in this issue cover a broad range of advanced areas summarized in the following sections: High harmonic generation: Advances in generation UV, VUV, and EUV light. Including single cycle pulse synthesis. Ultrafast lasers: New materials, and mid-IR laser technology. Non-linear optics: New laser light conversion techniques and ultrafast propagation in materials. Ultrafast chemistry: Advances in techniques using ultrafast lasers for chemistry applications. These key research topics are highlighted as comprehensive overviews of the current status and future trends, as well as original results and recent developments in the field of Ultrafast Science and Technology. This issue contains 25 papers, including 8 invited and 17 contributed papers authored by well-regarded research groups and scientists, both established and emerging, from all over the world. The invited papers include overviews on recent ultrafast

We demonstrate cascaded harmonic generation to 9 th harmonic (115nm) of 1040nm in a negative curvature hollow fiber filled with Xenon gas. By injecting the fundamental and second harmonic of a commercial ultrafast fiber laser at 1040nm and 520nm respectively, 3 rd harmonic is generated with sufficient efficiency to produce phase matched harmonics at the 4th (260nm), 5 th (205nm), 6 th (173nm), 7 th (148nm), 8 th (130nm), and 9 th (115nm) from a non-resonant cascaded harmonic generation process. © 2019 The Author(s)

Ultrafast fiber lasers have the potential to make applications of ultrashort pulses widespread - techniques not only for scientists, but also for doctors, manufacturing engineers, and more. Today, this potential is only realized in refractive surgery and some femtosecond micromachining. The existing market for ultrafast lasers remains dominated by solid-state lasers, primarily Ti:sapphire, due to their superior performance. Recent advances show routes to ultrafast fiber sources that provide performance and capabilities equal to, and in some cases beyond, those of Ti:sapphire, in compact, versatile, low-cost devices. In this paper, we discuss the prospects for future ultrafast fiber lasers built on new kinds of pulse generation that capitalize on nonlinear dynamics. We focus primarily on three promising directions: mode-locked oscillators that use nonlinearity to enhance performance; systems that use nonlinear pulse propagation to achieve ultrashort pulses without a mode-locked oscillator; and multimode fiber lasers that exploit nonlinearities in space and time to obtain unparalleled control over an electric field.

We present a monolithic, ultrafast, mid-infrared laser designed specifically for seeding an optical parametric chirped pulse amplifier. The compact laser system output nearly transform-limited pulses with MW class peak powers at repetition rates of ≥1MHz.

We inject the fundamental and second harmonic from a commercial ultrafast fiber laser into a Xe-filled negative curvature hollow waveguide, resulting in generation of coherent light to 9w (115 nm) through cascaded non-resonant wave mixing.

Consumer-driven technologies breathe life into the material of choice for ultrafast lasers.

We describe a system for automated modelocking and optimization of a fiber laser oscillator employing nonlinear polarization evolution. Using four liquid crystal variable retarders, we fully control the fiber launch and output polarization states, enabling compensation for mechanical and environmental perturbations to the fiber cavity. We demonstrate mapping of the modelocking regions for an ANDi fiber oscillator and demonstrate that local and global optimization algorithms can be used to maintain the laser in the same operating state. This technique enables robust operation of nonlinear polarization evolution modelocked fiber lasers, rivaling the stability of PM fiber lasers while maintaining the advantages of the NPE modelocking mechanism. (C) 2017 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

We introduce an optical parametric amplifier driven by a 3.5 μJ, 130 fs pulse at 1040 nm from a KMLabs Y-Fi HP. The optical parametric amplifier is seeded with white-light generated in a bulk YAG crystal. The net conversion efficiency into the short-wave infrared signal is as high 14%, and we are presently able to cover 1360–1800 nm (signal) and 2.35–4.15 μm (idler).

We report on a direct diode-pumped Ti:sapphire ultrafast regenerative amplifier laser system producing multi-μJ energies with a repetition rate from 50 to 250 kHz. By combining cryogenic cooling of Ti:sapphire with high brightness fiber-coupled 450nm laser diodes, we for the first time demonstrate a power-scalable CW-pumped architecture that can be directly applied to demanding ultrafast applications such as coherent high-harmonic EUV generation without any complex post-amplification pulse compression. Initial results promise a new era for Ti:sapphire amplifiers not only for ultrafast laser applications, but also for tunable CW sources. We discuss the unique challenges to implementation, as well as the solutions to these challenges.

We present a mid-IR OPCPA laser producing multi-mJ femtosecond pulses at 1kHz. The beam profile of the 3.1μm idler is excellent, enabling efficient coupling into high-gas-pressure waveguides, required for phase matched 1keV high harmonic generation.

We present a method for accessing all possible polarization states in a fiber oscillator allowing complete control of nonlinear polarization evolution using just four variable liquid crystal elements. We show automatic discovery of modelocking states as well as correction for environmental perturbations using an all-normal dispersion oscillator.

We demonstrate a direct diode-pumped Kerr Lens Modelocked Ti:sapphire laser producing 13 fs pulses with 1.85 nJ energy at 78 MHz (145 mW) using a single laser diode pump. We also present a similar laser using three spectrally combined diodes, generating >300 mW output power with >50 nm bandwidth. We discuss the use of far-from TEM00 pump laser sources, and their effect on the Kerr lens modelocking process.