Conference Agenda

Plasma mirrors driven at kHz-repetition-rate with waveform-controlled relativistic-intensity near-single-cycle laser pulses produce extreme ultraviolet spectral continua supporting isolated attosecond pulses with diffraction limited beam quality. A newly developed liquid leaf target yields unprecedented stability and duration of operation. This lifts a major obstacle to exploiting plasma mirrors as attosecond pulse sources.

We present studies on boosting high-harmonic generation (HHG) efficiency from solids in the extreme-ultraviolet (XUV) region by two-color non-collinear wave mixing in silica. Our results show that the conversion efficiency of two-color wave mixing exceeds that of single-color HHG by a factor of at least ten. We analyze the underlying mechanisms, revealing that the synergy between Floquet-Bloch dressing and inter- and intraband dynamics under laser irradiation enables efficient carrier excitation, enhancing harmonic yield. Integrating wave mixing into solid-state HHG could help establish compact, coherent XUV sources for applications where traditional gas-HHG is impractical.

Shaping of the spectrum of frequency comb sources is highly beneficial for application that require controllable optical source, such as ranging or communications. However, efficient in-situ reconfiguration of the spectrum is a challenge. We demonstrate spectral shaping of frequency combs in fast-gain active devices by engineering an Aharonov-Bohm phase in a synthetic frequency lattice. By modulating a fast gain circular laser at its resonance and twice this frequency with a relative phase, we created a triangular ladder in the modal space, where the phase added with staggered phase flux. This broke the time-reversal symmetry in the system, allowing for non-trivial gauge fields that manipulate the light. This enable the control over the frequency lattice dynamics, enabling full bandwidth tuning of a strong central lobe in a Quantum Cascade Laser comb. This paves the wave to new efficient and simple reconfigurable optical frequency comb sources.

Light beams exhibit two intrinsic quantized degrees of freedom: spin angular momentum (SAM) and orbital angular momentum (OAM) whose manipulation enables precise control over the topological characteristics of electromagnetic fields. Recently, structured fields formed from a non-separable combination of SAM and OAM have attracted significant interest. These fields correspond to eigenstates of the generalized angular momentum (GAM), an operator merging SAM and OAM components which can yield remarkable fractional eigenvalues. The conservation of GAM, observed through harmonic generation, suggests its potential significance as a fundamental quantum number. In this work, we extend the analysis by examining its conservation laws through second-harmonic generation within an underdense, isotropic, and inhomogeneous plasma; a process governed by dipole-forbidden interaction which implies spin-orbit coupling. Our findings indicate that the symmetry and topological properties of the field are disrupted, leading to conservation of the GAM charge only on average. This symmetry breaking provides an easily detectable signature of the driving field’s topology