arXiv subjects

Mohammed Sabbah

Publications and source records attributed to Mohammed Sabbah.

5 recordsLinked to original sources

arXiv2025

Tunable megawatt-scale sub-20 fs visible pulses from a fiber laser source

Ultrafast laser pulses that are both tunable in wavelength and very short in duration are essential tools in fields ranging from biomedical imaging to ultrafast spectroscopy. While resonant dispersive-wave emission in gas-filled hollow-core fibers is a powerful technique for generating such pulses, it has traditionally required complex and expensive pump laser systems. In this work, we present a more compact and accessible alternative that combines gain-managed nonlinear amplification with resonant dispersive-wave emission. Our system produces sub-20 femtosecond pulses tunable from 400 nm to beyond 700 nm, with energies up to 39 nJ and peak powers exceeding 2 MW, operating at a 4.8 MHz repetition rate. This compact and efficient laser source opens new avenues for deploying resonant dispersive-wave-based technologies for broader scientific and industrial applications.

physics.optics↗

arXiv2024

Resonance-free deep ultraviolet to near infrared supercontinuum generation in a hollow-core antiresonant fibre

Supercontinuum generation in the ultraviolet spectral region is challenging in solid-core optical fibres due to solarization and photodarkening. Antiresonant hollow-core fibres have overcome this limitation and have been shown to guide ultraviolet light at sufficient intensity for ultraviolet spectral broadening through nonlinear optics in the filling gas. However, their ultraviolet guidance is usually limited by discontinuities caused by the presence of high-loss resonance bands. In this paper, we report on resonance-free supercontinuum generation spanning from the deep ultraviolet to the near infrared achieved through modulation instability in an argon-filled antiresonant hollow-core fibre. The fibre was directly fabricated using the stack-and-draw method with a wall thickness of approximately 90 nm, enabling continuous spectral coverage from the deep ultraviolet to the near infrared. We also report numerical simulations to investigate the supercontinuum bandwidth and the factors limiting it, finding that the overall dispersion landscape, and associated group-velocity matching of cross-phase modulation interactions, is the dominant constraint on spectral extension.

physics.optics↗

arXiv2023

On-target delivery of intense ultrafast laser pulses through hollow-core anti-resonant fibers

We report the flexible on-target delivery of 800 nm wavelength, 5 GW peak power, 40 fs duration laser pulses through an evacuated and tightly coiled 10 m long hollow-core nested anti-resonant fiber by positively chirping the input pulses to compensate for the anomalous dispersion of the fiber. Near-transform-limited output pulses with high beam quality and a guided peak intensity of 3 PW/cm2 were achieved by suppressing plasma effects in the residual gas by pre-pumping the fiber after evacuation. This appears to cause a long-term removal of molecules from the fiber core. Identifying the fluence at the fiber core-wall interface as the damage origin, we scaled the coupled energy to 2.1 mJ using a short piece of larger-core fiber to obtain 20 GW at the fiber output. This scheme can pave the way towards the integration of anti-resonant fibers in mJ-level nonlinear optical experiments and laser-source development.

physics.optics↗

arXiv2023

The effect of rotational Raman response on ultra-flat supercontinuum generation in gas-filled hollow-core photonic crystal fibers

We experimentally and numerically investigate flat supercontinuum generation in gas-filled anti-resonant guiding hollow-core photonic crystal fiber. By comparing results obtained with either argon or nitrogen we determine the role of the rotational Raman response on the supercontinuum formation. When using argon, a supercontinuum extending from 350 nm to 2 μm is generated through modulational instability. Although argon and nitrogen exhibit similar Kerr nonlinearity and dispersion, we find that the energy density of the continuum in the normal dispersion region is significantly lower when using nitrogen. Using numerical simulations, we find that due to the closely spaced rotational lines in nitrogen, gain suppression in the fundamental mode causes part of the pump pulse to be coupled into higher-order modes which reduces the energy transfer to wavelengths shorter than the pump.

physics.optics↗

arXiv2023

Generation and characterization of frequency tuneable sub-15 fs pulses in a gas-filled hollow-core fiber pumped by a Yb:KGW laser

We investigate soliton self-compression and photoionization effects in an argon-filled antiresonant hollow-core photonic crystal fiber pumped with a commercial Yb:KGW laser. Before the onset of photoionization, we demonstrate self-compression of our 220~fs pump laser to 13~fs in a single and compact stage. By using the plasma driven soliton self-frequency blueshift, we also demonstrate a tuneable source from 1030 to ~700 nm. We fully characterize the compressed pulses using sum-frequency generation time-domain ptychography, experimentally revealing the full time-frequency plasma-soliton dynamics in hollow-core fibre for the first time.

physics.optics↗