Abstract:We present an ultrafast thin disk laser that generates an average output power of 275 W, which is higher than any other modelocked laser oscillator. It is based on the gain material Yb:YAG and operates at a pulse duration of 583 fs and a repetition rate of 16.3 MHz resulting in a pulse energy of 16.9 μJ and a peak power of 25.6 MW. A SESAM designed for high damage threshold initiated and stabilized soliton modelocking. We reduced the nonlinearity of the atmosphere inside the cavity by several orders of magnitude by operating the oscillator in a vacuum environment. Thus soliton modelocking was achieved at moderate amounts of self-phase modulation and negative group delay dispersion. Our approach opens a new avenue for power scaling femtosecond oscillators to the kW level. 435-453 (1996). 19201-19208 (2010). Huber, and U. Keller, "High-power ultrafast thin disk laser oscillators and their potential for sub-100-femtosecond pulse generation," Appl. Published in OpticsExpress 20, issue 21, 23535-23541, 2012 which should be used for any reference to this

We present a semiconductor saturable absorber mirror mode-locked thin disk laser based on Yb:Lu(2)O(3) with an average power of 141 W and an optical-to-optical efficiency of more than 40%. The ideal soliton pulses have an FWHM duration of 738 fs, an energy of 2.4 microJ, and a corresponding peak power of 2.8 MW. The repetition rate was 60 MHz and the beam was close to the diffraction limit with a measured M(2) below 1.2.

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Abstract:The kinetics of the OH + CO reaction, fundamental to both atmospheric and combustion chemistry, are complex due to the formation of the HOCO intermediate. Despite extensive studies on this reaction, HOCO has not been observed at thermal reaction conditions. Exploiting the sensitive, broadband, and high-resolution capabilities of time-resolved cavityenhanced direct frequency comb spectroscopy, we observe OD + CO reaction kinetics with the detection of stabilized trans-DOCO, the deuterated analogue of trans-HOCO, and its yield. By simultaneously measuring the time-dependent concentrations of both trans-DOCO and OD species, we observe unambiguous low-pressure termolecular dependence on the reaction rate coefficients for both N2 and CO bath gases. These results confirm the HOCO formation mechanism and quantify its yield. One Sentence Summary:We detect trans-DOCO and OD in the reaction of OD + CO using cavity-enhanced direct frequency comb spectroscopy and determine the kinetics and trans-DOCO branching yield in the low pressure regime. Main Text:2 The apparent simplicity of gas phase bimolecular reaction kinetics of free radicals often belies the complexity of the underlying dynamics. Reactions occur on multidimensional potential energy surfaces that can possess multiple pre-reactive complexes, bound intermediate complexes and multiple transition states. As a result, effective bimolecular rate coefficients often exhibit complex temperature and pressure dependence. The importance of free radical reactions in processes such as combustion and air pollution chemistry has motivated efforts to determine these rate constants both experimentally and theoretically. Quantitative ab initio modeling of kinetics remains a major contemporary challenge (1), requiring accurate quantum chemical calculations of energies, frequencies and anharmonicities, master equation modeling, energy transfer dynamics, and, when necessary, calculation of tunneling and non-statistical behavior.Experimentally, detection of the transient intermediates, which is the key to unraveling the dynamics, is often quite challenging. has been extensively studied over the last four decades because of its central role in atmospheric and combustion chemistry (2); it has come to serve as a benchmark for state-of-the-art studies of chemical kinetics of complex bimolecular reactions (3,4). In Earth's atmosphere, the hydroxyl radical OH is critical as the primary daytime oxidant (5, 6). CO, a byproduct of fossil fuel burning, acts through reaction 1 as an important global sink for OH radicals and is the dominant OH loss process in the free troposphere. In fossil fuel combustion, OH + CO is the final step that oxidizes CO to CO2 and is responsible for a large amount of heat released.The rate of reaction 1 is pressure dependent and exhibits an anomalous temperature dependence, which led Smith and Zellner (7) to propose that the reaction proceeds through a highly energized, strongly bound intermediate, HOCO, the hydrocarboxyl radical. Formation of H + CO2 produc...

Ultrafast thin disk laser oscillators achieve the highest average output powers and pulse energies of any mode-locked laser oscillator technology. The thin disk concept avoids thermal problems occurring in conventional high-power rod or slab lasers and enables high-power TEM 00 operation with broadband gain materials. Stable and self-starting passive pulse formation is achieved with semiconductor saturable absorber mirrors (SESAMs). The key components of ultrafast thin disk lasers, such as gain material, SESAM, and dispersive cavity mirrors, are all used in reflection. This is an advantage for the generation of ultrashort pulses with excellent temporal, spectral, and spatial properties because the pulses are not affected by large nonlinearities in the oscillator. Output powers close to 100 W and pulse energies above 10 µJ are directly obtained without any additional amplification, which makes these lasers interesting for a growing number of industrial and scientific applications such as material processing or driving experiments in high-field science. Ultrafast thin disk lasers are based on a power-scalable concept, and substantially higher power levels appear feasible. However, both the highest power levels and pulse energies are currently only achieved with Yb:YAG as the gain material, which limits the gain bandwidth and therefore the achievable pulse duration to 700 to 800 fs in It is important to evaluate their suitability for power scaling in the thin disk laser geometry. In this paper, we review the development of ultrafast thin disk lasers with shorter pulse durations. We discuss the requirements on the gain materials and compare different Yb-doped host materials. The recently developed sesquioxide materials are particularly promising as they enabled the highest optical-tooptical efficiency (43%) and shortest pulse duration (227 fs) ever achieved with a mode-locked thin disk laser.