Conference Agenda

Light revolutionized our vision of technology. Carrying five internal degrees of freedom, it offers unlimited capabilities in light-matter interactions. The recent advances in coherent light sources enable remarkable progress in harnessing degrees of freedom and boost light-induced applications. The further increasing demand for controlling the light states catalyzes technological innovations in laser-based systems. In this presentation, I will focus on our recent advances in developing laser systems capable of delivering high power optical vortices with exceptionally high modal purity. By employing the coherent beam combining technique in the filled-aperture configuration, we show the power scaling of short pulsed high-dimensional optical vortices up to 100 W and modal purity in the range of 92-97%.

We report on a MidIr source generating bursts of intense pulses with

tunable repetition rates in the GHz range. The wavelength is also adjustable

between 2.88 to 3.03 μm. The system is based on an electro-optic frequency

comb emitting at 1030 nm out of which bursts of ns duration are carved and

amplified to several W leading to significant pulse peak power. This Yb-based

fiber system is then used to pump an optical parametric amplifier seeded by a

tunable CW Er-doped fiber laser. Due to the second-order non-linear process

properties, the temporal and spectral structure of the pump are transferred to the

idler wave leading to a transient optical frequency comb in the MidIr spectral

range.

We report on the development of the first red diode-pumped fs regenerative alexandrite amplifier. For seeding the amplifier, we will utilize our previously developed SESAM modelocked red diode-pumped alexandrite oscillator, which generates sub-100-fs pulse durations with nJ pulse energy. We will then amplify these pulses to achieve a pulse energy of 10 μJ. We achieved a continuous-wave (CW) output power of up to 2.8 W with 8 W of pump power, and watt-level output power with up to 4% output coupling using additional amplifier components inside the cavity. This demonstrates that there is sufficient net gain for regenerative amplification.

Passively modelocked solid-state lasers can exhibit two types of instabilities with very different origins. Near threshold, pulses are prone to the Q-switching instability, where pulse energy shows strong periodic modulation over successive roundtrips. This behaviour disappears as the pump power increases, giving way to the fundamental modelocked state—characterized by a single stable pulse circulating in the cavity. At higher pump levels, this state can become unstable again, leading to the generation of multiple equidistant pulses per roundtrip, forming harmonic modelocking states with 2, 3, …, n pulses. These instabilities critically affect laser performance, especially in systems using slow saturable absorbers, where accurate modelling becomes particularly challenging. Despite their practical relevance, analytical expressions for the boundaries of these instability regimes are scarce. In this work, we derive such expressions from a recently proposed generalization of the Haus master equation, providing a compact framework to describe the onset of both Q-switching (QML) and harmonic modelocking (HML) in passively modelocked solid-state lasers. These results contribute to a deeper understanding of the dynamics involved and offer valuable guidance for experimental design and optimization.

We report the post-compression of 180 fs pulses with 610 μJ pulse

energy to 44 fs using an LG0,3 beam in a compact bulk multi-pass cell. As a

result, the peak power of an Ytterbium laser system is boosted from 2.5 GW to

9.1 GW and the topological charge of the beam is shown to be conserved after

compression.