arXiv subjects

Florian Kiesel

Publications and source records attributed to Florian Kiesel.

4 recordsLinked to original sources

arXiv2026

AOM-based ultra-low noise laser intensity control up to the MHz range

High-power laser sources that exhibit low relative intensity noise and allow simultaneous dynamic control of their light level are required for a broad range of applications in various fields of physics. Acousto-optic modulators (AOMs) are widely used for active power stabilization and regulation due to their simple drive electronics requirements and high optical power handling capability in free-space. However, the rather slow propagation speed of the sound wave within the AOM crystal typically limits their control bandwidth to a few hundred kHz. In this work, we present a novel AOM-based control system that is capable of significantly suppressing intensity noise of high-power lasers up to the MHz range. By combining two standard feedback loops with one feedforward control branch and optimizing the beam path in the AOM crystal, ultra-low relative intensity noise levels down to $-155\, \text{dB}\,\text{Hz}^{-1}$ even at several hundred kHz are achieved. Our results are relevant for applications that require ultra-low intensity noise at Fourier frequencies up to the MHz range, such as optical lattice experiments with light ultracold atoms.

physics.optics↗

arXiv2026

Isothermal compression of a Fermi gas to deep quantum degeneracy

The standard approach for generating deeply degenerate quantum gases is evaporative or sympathetic cooling in a harmonic trap, after which the gas has reached its minimum entropy. All subsequent state transformations rely on adiabatic changes of a closed system, and coupling to the environment or non-adiabatic processes monotonically increase the entropy. Here, we demonstrate that this experimental paradigm can be bypassed by utilizing species-selective trapping with a low-dissipation optical tune-out trap in a dual-species mixture. We successfully reduce the entropy of a two-component fermionic quantum gas via isothermal compression within a bosonic bath, reaching deep quantum degeneracy of $T/T_F = 0.024^{+0.007}$, with $T_F$ the Fermi temperature. By characterizing the cross-dimensional relaxation and thermalization, we demonstrate that cooling light fermions with heavy bosons remains efficient and fast, even deep in the degenerate regime, where the thermalization time is found to be independent of $T/T_F$. Our results pave the way for direct cooling within optical lattices, box traps, or other complex potentials, thereby eliminating the reliance on adiabatic state transformations to reach strongly interacting many-body regimes.

cond-mat.quant-gas↗

arXiv2025

Dissipationless tune-out trapping for a lanthanide-alkali quantum gas mixture

Quantum gas mixtures offer a wide field of research, ranging from few-body physics of impurities to many-body physics with emergent long-range interactions and ultracold molecular gases. Achieving precision control of mixtures is much harder than for single-component gases and, consequently, the respective techniques are less developed. Here we report on a decisive step forward in this direction by realizing dissipationless and fully differential optical control of the motional degrees of freedom of one of the species without affecting the other. This is achieved in a novel Bose-Fermi mixture with extreme mass imbalance, erbium-166 and lithium-6. Our experiments pave the way to a new generation of precision many-body experiments with quantum gas mixtures with unprecedented long lifetimes and low temperatures.

cond-mat.quant-gas↗

arXiv2024

Long-term stable laser injection locking for quasi-CW applications

Generating high output powers while achieving narrow line single mode lasing are often mutual exclusive properties of commercial laser diodes. For this reason, efficient and scalable amplification of narrow line laser light is still a major driving point in modern laser system designs. Commonly, injection locking of high-power semiconductor laser diodes are used for this purpose. However, for many laser diodes it is very challenging to achieve stable operation of the injection locked state due to a complex interplay of non-linearities and thermal effects. Different approaches of active or passive stabilization usually require a large overhead of optical and electrical equipment and are not generally applicable. In our work we present a passive stabilization scheme, that is generally applicable, technically easy to implement and extremely cost-effective. It is based on the externally synchronized automatic acquisition of the optimal injection state. Central to our simple but powerful scheme is the management of thermalization effects during lock acquisition. By periodical relocking, spectrally pure amplified light is maintained in a quasi-CW manner over long timescales. We characterize the performance of our method for laser diodes amplifying 671 nm light and demonstrate the general applicability by confirming the method to work also for laser diodes at 401 nm, 461 nm and 689 nm. Our scheme enables the scaled operation of injection locks, even in cascaded setups, for the distributed amplification of single frequency laser light.

physics.optics↗