Figure 43 - uploaded by Clément Paradis
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a) Schematic of the SESAM mode-locked laser oscillator. BP, Brewster plate; OC, output coupler; CM1, concave mirror with a 3-m radius of curvature (RoC); CM2, 0.4-m-RoC convex mirror; CM3, 0.75-m-RoC concave mirror. Other mirrors are dispersive mirrors. b) Picture of the large-size high-power SESAM. c) Output-beam profile of the mode-locked laser at 27-W average power.
Source publication
In this work, recent achievements in the field of ultrafast thin-disk lasers (TDLs) are discussed. The novel ultrafast Yb-based TDL oscillators presented in this thesis show improved performance at sub 100 fs pulse duration. Benefiting from the fruitful combination of the Kerr lens mode locking scheme and the broad emission of the gain materials, T...
Citations
... Nonlinear passive modulation methods, such as Kerr-lens mode-locking (KLM), are more suited for producing ultrashort pulses [22]. The main disadvantage of Kerr lens modelocked lasers is their resonator design, which often necessitates operating near a stability edge and links the spatial and temporal soliton dynamics [23]. ...
High average-power laser pulses are essential for spectroscopy applications at a high repetition rate. These features in the short-wave infrared regime (0.7-2.5 um) are interesting for molecular fingerprinting and low-order high-harmonic generation from solids.
In this spectrum window, the wavelength of 2 um opens the gate to remotely detecting the presence of greenhouse gases such as methane molecules in the air. The high average-power laser provides a strong signal in the gas phase, and the high repetition rate decreases the duration of measurements and reaches the shot noise. While this feature is feasible with direct lasers such as Tm-based fibre or mode-locked lasers, the carrier-envelope phase stability prioritizes the nonlinear methods. This output is possible by a high average-power pump at 1 um at a high repetition rate and down-conversion to 2 um. The high efficiency of optical parametric oscillators and wide phase-matching bandwidth lead to high average-power broadband pulses in the wavelength of interest.
This work presents and experimentally demonstrates a watt-level sub-100 femtosecond Optical Parametric Oscillator (OPO) synchronously pumped by a multi-megahertz repetition-rate thin-disk Yb:YAG oscillator. The procedure to design a synchronously pumped optical parametric oscillator is described, and the vital factors in high-power performance and challenges are documented and considered here. Moreover, the active stabilization of the system by implementing dither locking is explained.
The output is self-phase locked pulses at the wavelength of 2060 nm with 1 Watt of average power for the 0.5 mm Periodically Poled Lithium Niobate (PPLN).
... TDLs is very instructive [37,102]. ...
... Lastly, from the different negative dispersion mirrors that were tried, it seemed that the pulse duration and the TBP were highly affected by the design and quality of the coatings, specially by the flatness of the GDD curve at the gain bandwidth. This is explored in more detail in [102,129]. A strong indication that in order to push the limits of short pulse formation, optimization of all cavity parameters is crucial. ...
... When it comes to the scaling of the output power of materials with gain bandwidths capable of delivering sub-100-fs pulses, fantastic works have been already presented, with the demonstration of 21 W of average power from a Yb:LuO TDL, boasting pulses with a duration of 95 fs [38]. However, further scaling laser systems which can deliver sub-50-fs will always prove challenging as the observed efficiency from these systems decreases drastically [102] and perhaps a paradigm shift -such as similaritons [189] or quartic solitons [190] -will be needed to achieve the optical-to-optical efficiency observed by TDLs operating at longer pulse durations, where again, it is hoped that the information provided in this thesis will be of a helpful nature. ...
Titanium doped sapphire (Ti:sapphire) systems are the backbone of current ultrafast technology and they are invaluable research tools in contemporary science. However, little progress was observed in their average power scaling due to lack of suitable pumping systems, therefore, no Ti:sapphire laser in the kilowatt-class exists. In contrast, ytterbium (Yb) doped gain media is cementing itself as the new-wave of ultrafast technology. Enabled by the diminished costs of high-grade crystal production for industrial applications, maturity of optics and the developments of high power laser diodes able to pump these gain media, Yb-doped solid-state laser are more cost effective, compact and of lower complexity when compared to titanium doped sapphire systems. Not only does this makes them attractive for industrial applications, but their lowered complexity and cost mean that their further dissemination through the scientific world becomes easier, opening the doors to cutting-edge research in every scientific subject.
Within this frame, the development aspects of compact high power ultrafast thin-disk laser oscillators based on Yb gain media will be given. Not only about their design and implementation, but also on how to further improve a system by its post-compression and implementing carrier-envelope offset (ϕ CEO ) locking. At the core of this work is the understanding and effective implementation of hard-aperture Kerr-lens mode-locking which enables a successful exploitation of the gain bandwidth offered by these gain media.
The work being reported in this thesis aims to deliver several of the important aspects and hurdles which may be encountered while implementing a state-of-the-art high-power system and also provide a groundwork to future developments by the demonstration of two things: first, how to improve existing numerical methods to help with the design of high-power oscillators and second, give a detailed guide towards the ϕ CEO locking of such systems.
