Idler-resonant femtosecond optical parametric oscillator with high mid-infra-red beam quality

We report an idler-resonant femtosecond optical parametric oscillator (OPO) with average output power of 520 mW, repetition-rate of 80 MHz, pulse duration of 90 fs and nearly diffraction-limited beam quality at ~2.4 µm

Single exposure wavefront curvature estimation of high harmonic radiation by diffraction from a regular array

We present a novel technique for estimating the radius of curvature from a single exposure of EUV light from a high harmonic source diffracted by a grating of square apertures

Simulations and experiments showing the origin of multiwavelength mode locking in femtosecond, Yb-fiber lasers

A stable and self-starting femtosecond breathing-pulse Yb-fiber oscillator is reported, mode-locked using the nonlinear polarization evolution mechanism. A bifurcation between two distinct modes of operation is demonstrated experimentally, producing pulses with a single central wavelength in one state, or following adjustment of the intracavity waveplates, the emission of pulses with three distinct central wavelengths. The maximum bandwidth was 72 nm at the-10 dB level, and the pulses were compressible externally to 70 fs with energies of 0.75 nJ. The multiwavelength pulses reported here are significantly shorter than the picosecond pulses previously observed from similar mode-locked multiwavelength sources. Vector simulations based on the nonlinear Schrödinger equation show that the multiwavelength behavior is produced by overdriving the nonlinear polarization evolution-based saturable absorber at the peak of the pulse, leading to transmission of the two wings of the strongly chirped pulse. This new insight shows clearly that the three pulses output in the multiwavelength state are coherent. The agreement between simulation and experimental data shows nonlinear polarization evolutionbased mode-locked fiber lasers are a suitable platform for studying the nonlinear dynamics underlying the bifurcation of the output. © 2016 Optical Society of America

Advances in high power short pulse fiber laser systems and technology

We review recent advances in Yb fiber lasers and amplifiers for high power short pulse systems. We go on to describe associated recent developments in fiber components for use in such systems. Examples include microstructured optical fibers for pulse compression and supercontinuum generation, and advanced fiber grating technology for chirped-pulse amplifier systems

Mid-IR coherent supercontinuum generation in all-solid step-index soft glass fibers

We numerically demonstrate that normal dispersion femtosecond pumping of tailored soft glass step-index fibers can generate highly coherent mid-IR supercontinuum light with two octaves bandwidth, suitable for recompression to few-cycle pulse durations

Pulsed fibre laser and amplifier systems

Tremendous progress has been made over recent years in the development of high-power fibre laser systems. Gone are the days when fibre lasers were perceived as an irrelevant curiosity offering interesting performance features but always at a power level that seemed inadequate for all but a few niche applications. Improvements in high-power, high-brightness multi-mode pump lasers, coupled with the development of cladding-pumped laser technology, have changed that view. It is now widely appreciated that the excellent heat dissipation characteristics of fibre along with the high efficiencies (often greater than 80%), actually make fibre lasers a front runner for many high power laser applications and in particular those that require the generation of high average power continuous-wave radiation. Average power levels of 110W have already been reported for a fibre laser and there is significant potential for scaling the power levels still higher. Whilst such arguments have proved compelling from the continuous wave laser perspective the suitability of fibre based systems for pulsed laser and amplifier systems is less obvious. In a conventional single-mode fibre light is confined within a mode with a characteristic diameter of order 5-10µm. This limits the energy storage of the medium and compromises laser operation for applications, such as Q-switching, which critically depend on this. Furthermore, fibres are inherently nonlinear and the tight mode confinement limits the pulse peak powers that can be reliably generated, or transmitted, through the system. Fortunately however it is possible to reduce the impact of such limitations by using advanced large mode-area single-mode fibre designs, or by going to multi-mode cores which offer even larger mode-areas. The key to successfully using the later is to manage the mode-selection and mode-coupling issues that naturally arise in order to ensure good spatial mode-quality output. Using such an approach it is possible to increase by more than two orders of magnitude the pulse energies attainable from both fibre laser, and seeded MOPA systems. For example we recently achieved ~8mJ pulses from a Q-switched fiber laser thereby opening up the possibility of using such sources for applications such as LIDAR that were previously considered incompatible with the pulse energies achievable with fibre technology. Moreover using techniques such as fibre based chirped pulse amplification it is possible to construct femtosecond pulse sources operating at several hundred pJ pulse energies and at multi-watt average power levels. Such sources are suited to a range of applications ranging from scientific research through to materials processing. In this presentation we review the latest advances in pulsed fibre laser and amplifier systems operating from the nanosecond to femtosecond regime. We discuss a number of the key application areas for such technology and conclude by making predictions for future research directions and ultimate performance limits

Holey fiber amplifiers and lasers

We review our recent activities in the development of small-core, active holey fibers and describe a number of experiments that highlight the advantages of this technology within a range of both linear and nonlinear devices

Silica holey fibres: fabrication and nonlinear effects

Holey fibres (HFs) [1] have emerged as a novel class of optical fibres which can provide completely new optical properties, such as endlessly single mode operation and novel dispersion properties as anomalous dispersion below 1.3µm, broadband flat dispersion and highly normal dispersion at 1.55µm. Moreover by changing the HF parameters (i.e. hole and core size), it is possible to fabricate HFs with an effective area so high as 800µm2 or so low as approximately 1µm2 [2]. A holey fibre perform is fabricated by stacking silica rod and capillaries inside a silica tube. This perform is then drawn to a fibre using a conventional fibre drawing equipment.In particular we will discuss the basic fabrication procedure for the production of HFs with a very high nonlinearity, and describe recent progress in nonlinear applications of HFs.For example we have demonstrated for the first time a HF-based Brillouin laser. This experiment used a robust silica jacketed HF with a 1.5µm core, a 100µm outer diameter (see figure 1) and an effective area of 2.85µm2. The laser threshold was found to be 125mW, and the slope efficiency ~70% [3].By using the same fibre perform and modifying the drawing parameters during the fabrication process, we obtained a different HF with a standard outer dimension of 125µm and a 2µm core. Using this fibre we achieved ultra-broad supercontinuum generation, as shown in figure 2, by launching 20kW peak power pulses at 1.06µm into 7 meter fibre length[4].Fig 1. SEM of a HF with a 1.5µm coreFig 2. Broadband continuum spectr

Supercontinuum generation and nonlinearity in soft glass fibers

The optical fiber based supercontinuum source has recently become a significant scientific and commercial success, with applications ranging from frequency comb production to advanced medical imaging. This one-of-a-kind book explains the theory of fiber supercontinuum broadening, describes the diverse operational regimes and indicates principal areas of applications, making it a very important guide for researchers and graduate students. With contributions from major figures and groups who have pioneered research in this field, the book describes the historical development of the subject, provides a background to the associated nonlinear optical processes, treats the generation mechanisms from continuous wave to femtosecond pulse pump regimes and highlights the diverse applications. A full discussion of numerical methods and comprehensive computer code are also provided, enabling readers to confidently predict and model supercontinuum generation characteristics under realistic conditions

Modelling pulse compression in BBO using cascaded nonlinearity: the effects of self-steepening in quadratic media

In a χ(2) material such as BBO, third order nonlinear effects can occur efficiently via a cascaded nonlinearity where light is rapidly converted from the fundamental to the second harmonic and back again with an intensity dependant phase shift. This cascaded nonlinearity has been used to demonstrate a wide range of χ(3) effects such as soliton propagation and compression. Here we study soliton-like pulse compression in a BBO crystal of 100fs input pulses looking to see the minimum pulse duration that can be obtained. Included for the first time in a systematic study is the χ(2) self steepening term[1] which we have found plays a significant role in the pulse dynamics