Advances in Ultrafast Optics Unlock Attosecond Control of Few-Cycle Laser Pulses

Controlling light at its most fundamental level , on attosecond timescales , presents a significant challenge for modern optics. Researchers Mohamed Sennary and Javier Rivera-Dean, from the University of Arizona and ICFO respectively, alongside Maciej Lewenstein and Mohammed Th. Hassan, demonstrate a novel approach to generating and manipulating squeezed light with unprecedented temporal precision. Their work introduces a light field squeezer which overcomes limitations in broadband phase-matching, allowing for the creation of intensity- and phase-squeezed states directly from few-cycle laser pulses. This breakthrough enables attosecond control over the characteristics of ultrafast light, offering potential advancements in fields such as strong-field physics and solid-state systems. By revealing a time-dependent squeezing distribution and demonstrating control over high-harmonic emission, the team has extended the possibilities for optical manipulation into the realm of the incredibly small and fast.

Attosecond Pulse Generation via High-Harmonic Generation The generation

The generation and control of attosecond pulses has revolutionised the study of electron dynamics in atoms, molecules, and materials. This field, known as attosecond science, relies on the development of novel techniques to create and characterise extremely short pulses of light, typically in the extreme ultraviolet (XUV) region of the electromagnetic spectrum. High-harmonic generation (HHG) is the dominant method for producing these attosecond pulses, where intense femtosecond laser pulses interact with a gaseous medium to generate coherent XUV radiation. Optimising HHG efficiency and controlling the properties of the generated attosecond pulses are central challenges in the field.

Recent advances have focused on shaping the driving laser field to tailor the attosecond pulse characteristics. Techniques such as pulse shaping and the use of complex laser waveforms allow for the control of the harmonic spectrum and the resulting attosecond pulse duration and intensity. Furthermore, the incorporation of advanced theoretical models and numerical simulations has been crucial for understanding the underlying physics of HHG and for guiding the development of new control strategies. These theoretical frameworks often involve solving the time-dependent Schrödinger equation for the interacting electron and laser fields.

Beyond pulse shaping, significant effort has been directed towards exploiting the quantum properties of the HHG process itself. Quantum interference effects between different harmonic orders can be harnessed to enhance specific harmonic components or to suppress unwanted ones. This allows for the creation of attosecond pulses with tailored spectral properties and improved coherence. Moreover, the use of multi-dimensional coherent spectroscopy in the XUV regime provides a powerful tool for probing the electronic structure and dynamics of matter with unprecedented temporal resolution. The applications of attosecond science are rapidly expanding.

Investigations into fundamental processes such as photoionisation, electron diffraction, and charge migration are providing new insights into the behaviour of electrons in complex systems. Furthermore, the development of attosecond microscopy promises to enable the direct imaging of electronic processes at the atomic scale. Future research directions include the exploration of novel materials for HHG, the development of more efficient and compact XUV sources, and the extension of attosecond techniques to the study of condensed matter systems and chemical reactions.

Attosecond Squeezed Light Generation and Characterisation Researchers have

Researchers pioneered a light field squeezer (QLFS) to generate and control ultrafast broadband squeezed light at the attosecond level. The study employed degenerate four-wave mixing within a quasi-collinear focusing geometry, a technique that overcomes limitations of conventional broadband phase-matching. This approach directly produces intensity- and phase-squeezed states originating from few-cycle laser pulses, enabling unprecedented control over the light’s properties. The team then harnessed ultrafast optical metrology to reveal a time-dependent squeezing distribution across individual half-cycles of the electric field, a crucial step towards manipulating light at its fundamental timescales.

To characterise the squeezed light, scientists sampled the few-cycle pulse waveform using a dielectric reflectivity method. The intensity difference was extracted from statistics gathered across numerous shots and rigorously benchmarked against coherent-state reference measurements to ensure observed spectral structures represented genuine quantum uncertainty redistributions. Analysis revealed a quasi-similar trend in intensity uncertainty each half-cycle, contrasting sharply with the random behaviour observed in classical coherent light fields. Zooming in on a single half-cycle, the research demonstrated that the squeezing level varied with time, reaching a minimum at zero intensity and increasing towards the half-cycle maximum.

Further investigation involved simulations of high-harmonic generation (HHG) driven by five distinct field types. These included coherent light, symmetrically squeezed fields, and variations of time-dependent squeezed fields. The resulting HHG spectra showed that intensity-squeezed fields produced spectra with reduced cut-offs, while phase-squeezed and time-dependent fields yielded broader bandwidths. Calculations of the second-order correlation function revealed that time-dependent squeezing imprinted itself onto the HHG process, influencing both the harmonic spectrum and photon statistics. This work establishes a clear link between the driving field’s quantum properties and the characteristics of the generated high-harmonic radiation.

Attosecond Squeezed Light Generation and Control

Scientists have achieved a breakthrough in quantum optics with the development of a light field squeezer (QLFS) capable of generating and controlling ultrafast broadband squeezed light at the attosecond timescale. The team employed degenerate four-wave mixing in a quasi-collinear focusing geometry, successfully overcoming conventional broadband phase-matching limits to produce both intensity- and phase-squeezed states directly from few-cycle laser pulses centered at 790nm. Experiments revealed a time-dependent squeezing distribution across individual half-cycles of the electric field, demonstrating a level of control previously unattainable in ultrafast optics. Measurements confirm that the QLFS generates squeezed light with a broad bandwidth, effectively addressing limitations inherent in traditional quantum nonlinear optics.

Researchers evaluated the intensity uncertainty by calculating integrated spectral intensity fluctuations, comparing them to the input coherent light, and establishing the presence of squeezing. Further analysis correlated intensity and phase uncertainty, providing a comprehensive characterization of the generated quantum states. This detailed metrology allows for visualization of inferred effective Wigner representations of the light field, offering a direct assessment of the quantum state’s evolution. The breakthrough delivers attosecond precision in controlling squeezing characteristics by tuning both the relative pulse delay and the phase-matching angle.

By manipulating these parameters, scientists directly engineer the squeezed quadrature and quantum uncertainty level, opening new possibilities for quantum state engineering. Tests prove that quantum light-induced tunneling current is sensitive to the nonclassical intensity-noise statistics of the driving squeezed light, enabling sub-femtosecond control over this fundamental process. Results demonstrate that the temporal redistribution of uncertainty reshapes high-harmonic emission, highlighting the potential for manipulating strong-field interactions with tailored quantum light sources. The study extends the generation, control, and phase-space representation of squeezed light into the ultrafast and attosecond regimes, paving the way for advancements in strong-field and solid-state systems. This work establishes a practical path toward ultrafast quantum metrology and real-time quantum-state engineering, forming the foundation of a new era in ultrafast quantum optics.

Ultrafast Squeezed Light and Temporal Control

This work introduces a quantum light field squeezer capable of generating and actively controlling squeezed states of light across a broad spectrum. By employing degenerate four-wave mixing within a quasi-collinear geometry, researchers overcame limitations typically encountered in broadband phase-matching, successfully producing both intensity- and phase-squeezed states from few-cycle laser pulses. Detailed ultrafast optical metrology then revealed a time-dependent distribution of squeezing across individual half-cycles of the electric field, demonstrating a new level of control over quantum light. The significance of these findings lies in extending the manipulation of squeezed light into.