High power, broadly tunable all-solid state synchronously-pumped lithium triborate optical parametric oscillator

The past few years have seen major advances in optical parametric oscillators (OPOs), based on new nonlinear materials, such as lithium triborate (LBO) and capitalising on the availability of improved pump sources having high power and high spatial and spectral coherence. An area of particularly rapid development has been that of synchronously-pumped OPOs, exploiting the wide gain-bandwidth, which allows efficient pumping with short (picosecond or less) pump pulses. In this presentation we describe the performance of an optimised singly-resonant LBO OPO in which a number of significant improvements have been made over previously reported results. These improvements include greater available pump powers, by making use of a diode-pumped Nd:YLF amplifier stage, a fully optimised resonant frequency doubler, also based on lithium triborate as well as the introduction of cavity length (and hence oscillation wavelength) stabilisation of the OPO and the addition of chirp compensation in the OPO. The full tuning range available from 0.65 to 2.65µm is realised in this device. With the increased available pump power we can routinely obtain > 180mW (>90mW) average output power for the signal (idler) waves respectively. These increases in average output power have meant a consequent increase in intracavity peak power. This has led to the observation of significant chirp on the emitted picosecond pulses due to the combined effects of self-phase modulation (SPM) and group velocity dispersion (GVD). Emphasis in this presentation will be given to the results achieved through compensation of the chirp via the inclusion of negative GVD through an SF10 prism pair. We will also describe an active cavity length stabilisation system introduced in order to improve the long term stability both in amplitude and wavelength which has proved both very easy to implement and extremely reliable. Typical values of stability are now ~3% rms. amplitude noise, mainly from the resonant frequency doubler, and ~10-20 GHz linecentre variance

FastJet user manual

FastJet is a C++ package that provides a broad range of jet finding and analysis tools. It includes efficient native implementations of all widely used 2-to-1 sequential recombination jet algorithms for pp and e+e- collisions, as well as access to 3rd party jet algorithms through a plugin mechanism, including all currently used cone algorithms. FastJet also provides means to facilitate the manipulation of jet substructure, including some common boosted heavy-object taggers, as well as tools for estimation of pileup and underlying-event noise levels, determination of jet areas and subtraction or suppression of noise in jets.Comment: 69 pages. FastJet 3 is available from http://fastjet.fr

Broadly tunable all-solid-state picosecond LBO optical parametric oscillator

We report a synchronously-pumped optical parametric oscillator with a tuning range of 0.72-1.91µm, average output powers up to 89mW and pulse durations of 1.5psec

CW synchronously pumped optical parametric oscillators in periodically poled LiNbO₃

Synchronous-pumping of optical parametric oscillators in periodically-poled LiNbO3, with 0.5235µm and 1.047µm pumps confirm its suitability for short pulse operation. Tuning from 0.883-1.285µm and 1.67-2.806µm is demonstrated. Prospective tuning is to ~5µm

1.047µm synchronously pumped optical parametric oscillator in bulk periodically poled LiNbO₃

Picosecond pulses have been efficiently generated over the tuning range 1.670-2.806 µm via cw 1.047µm synchronously pumped optical parametric oscillation in periodically poled lithium niobate. Average signal and idler powers as high as 120mW and 90mW respectively have been generated with an overall slope efficiency of 61%. The corresponding pump depletion was 75% at 3 times above threshold

Feedback-controlled prelasing: a technique for pulse amplitude and frequency stabilisation of Q-switched lasers

A reliable single-frequency Q-switched laser with high pulse repetition frequency (PRF) and good pulse to pulse stability is desirable for many applications, including those where a high average power is required. One popular approach for obtaining single-frequency operation of Q-switched lasers is to use the technique of prelase Q-switching, where a low power single-frequency oscillation is established prior to opening the Q-switch. In practice this technique has been limited to low PRFs (typically < or = 1kHz) since the prelase usually begins with strong spiking behaviour followed by relaxation oscillations. These take a time to decay to the steady prelase required for reliable single-frequency operation and high pulse to pulse stability. At high PRFs, when the Q-switched pulse builds up from prelase spikes, large fluctuations in pulse amplitude and excessive timing jitter occur. In this paper we report a new technique involving actively controlling the diffraction loss of the Q-switch, so as to damp out spiking and relaxation oscillation. We have applied this technique to a Nd:YAG ring laser, pumped by a 1.2W high-brightness diode, in which a single acousto-optic modulator enforces unidirectional operation and is used to Q-switch the laser

Green-light generation of picosecond pulses in first-order quasi-phase-matched lithium niobate

Bulk periodically poled lithium niobate has been used for efficient first-order quasi-phase matched second harmonic generation of green light in the picosecond regime. We measured an effective nonlinear coefficient of ~14 pm/V

Synchronous pumping of an optical parametric oscillator using an amplified quasi-cw pump envelope

Pulse-slicing from a cw laser output followed by high gain amplification can produce quasi-cw pulses at power levels well in excess of those available from large frame cw lasers. Mode-locked pulse trains with an envelope of 10µs duration and at 2kHz repetition rate are amplified by a factor of 20 to give 5 Watts of envelope average power. These power levels allow efficient single-pass frequency doubling and subsequent pumping of a lithium triborate optical parametric oscillator

Jets in Hadron-Hadron Collisions

In this article, we review some of the complexities of jet algorithms and of the resultant comparisons of data to theory. We review the extensive experience with jet measurements at the Tevatron, the extrapolation of this acquired wisdom to the LHC and the differences between the Tevatron and LHC environments. We also describe a framework (SpartyJet) for the convenient comparison of results using different jet algorithms.Comment: 68 pages, 54 figure

Structure of Fat Jets at the Tevatron and Beyond

Boosted resonances is a highly probable and enthusiastic scenario in any process probing the electroweak scale. Such objects when decaying into jets can easily blend with the cornucopia of jets from hard relative light QCD states. We review jet observables and algorithms that can contribute to the identification of highly boosted heavy jets and the possible searches that can make use of such substructure information. We also review previous studies by CDF on boosted jets and its measurements on specific jet shapes.Comment: invited review for a special "Top and flavour physics in the LHC era" issue of The European Physical Journal C, we invite comments regarding contents of the review; v2 added references and institutional preprint number