arXiv subjects

Caroline Juliano

Publications and source records attributed to Caroline Juliano.

4 recordsLinked to original sources

arXiv2026

Multiscale carrier-envelope phase characterization of 2-μm pulses delivered by a 200-kHz optical parametric amplifier

Light fields with a central wavelength of 2 um are very well suited for strong-field-driven charge carrier control: Their photon energy lies far below the band gap of many materials, while their oscillation period remains significantly shorter than the coherence time of charge carrier oscillations. The resulting potential for field-driven charge carrier control is contingent on the reproducibility of the field structure of such ultrashort laser pulses. Here, we present a compact 200-kHz laser system that delivers ultrashort pulses with a duration of less than 20 fs in the spectral range around 2 um and with a pulse energy of 25 uJ. The electric field structure of the 2-um pulses is characterized in detail. In particular, the carrier-envelope phase (CEP) is measured over a wide range of timescales, from microseconds to hours. Passive stabilization due to difference frequency generation results in a root mean square value of carrier-envelope phase noise of less than 70 mrad over all measured time scales. The applicability of the pulses is demonstrated by measuring CEP-dependent high-order harmonic spectra with energies of up to 160 eV.

physics.optics↗

arXiv2026

Optical parametric multi-pass cell amplifier

Ultrafast lasers with simultaneously high average and peak power have become indispensable for driving a multitude of applications, including high-harmonic generation, strong-field physics, and particle source applications. Both parametric amplifiers and post-compressed Ytterbium lasers have emerged as prime platforms to meet these demands. While multi-pass cell (MPC) based post-compression offers broadband output with high beam quality, it provides limited wavelength tunability and suffers from temporal contrast degradation. Conversely, optical parametric amplifiers (OPAs) provide spectral tunability and high temporal contrast but they are limited by low pump-to-signal conversion efficiency and spatial beam inhomogeneities. Here, we introduce the Optical Parametric Multi-Pass Cell Amplifier (OPMPC), a hybrid architecture that overcomes the limitations of both schemes. Our approach utilizes two non-collinearly intersecting MPCs providing broadband parametric amplification of the seed pulses and complete idler removal after each pass through the crystal, thereby suppressing back-conversion. We experimentally demonstrate a record pump-to-signal power conversion efficiency of 43% using a 1030 nm pump at a 1 kHz repetition rate with a pulse energy of 174 $μ$J. The amplified signal at 1500 nm exhibits excellent beam quality, power and spectral stability and is compressed to 48 fs, demonstrating a new platform for ultrafast pulse generation.

physics.optics↗

arXiv2025

THz emission from multiple ionized plasma

Studies employing nonlinear interactions of THz pulses are nowadays a promising scientific research field. To capture these phenomena, THz pulses with energy ranging from hundreds of \muJ to the mJ level are necessary. However, techniques that provide pulses with such energy levels are still not widely established. Upscaling methods of laser-solid interaction is limited by the damage threshold of materials, while the mechanism of THz generation from high intensity laser-gas interactions is not fully understood yet. Here, we establish the photocurrent model of laser-driven plasma THz generation in the high-intensity regime by accounting for high-ionization states of the target gas. Our model shows excellent agreement with experimental observations, provides a clear explanation of phenomena in both spectral and temporal domains, and explains the high conversion efficiency from laser to THz. In the experiments, we achieved a generation of 0.2 mJ THz pulses, driven by a Ti:sapphire laser with a conversion efficiency exceeding 1 %.

physics.plasm-ph↗

arXiv2021

Direct (3+1)D laser writing of graded-index optical elements

We propose single-step additive fabrication of graded-index optical elements by introducing the light exposure as the additional dimension to three-dimensional (3D) laser writing, hence (3+1)D writing. We use a commercial printer and photoresist to realize the proposed single step fabrication method that can be swiftly adopted for research and engineering. After presenting the characterization of the graded-index profiles via basic structures, we demonstrate two different optical devices: volume holograms that are superimposed using angular and peristrophic multiplexing, and optical waveguides with well-defined refractive index profiles. In the latter, we precisely control the propagating modes via tuning the (3+1)D-printed waveguide parameters and report step-index and graded-index core-cladding transitions.

physics.optics↗