Ultrafast optics and structured light create light springs

Did you know that light can be shaped like a spring? An international team of researchers, led by Marco Piccardo, has achieved this feat using ultrafast optics and structured light. They have synthesized a new type of light beam called “light springs” in the laboratory. This groundbreaking discovery, published in Nature Photonics, has the potential to revolutionize photonics applications involving complex light.

In ultrafast optics, researchers can manipulate the duration of extremely short optical pulses, which can be as brief as a few femtoseconds (thousandths of billionths of a second). Pulse shaping, a technique employed in this field, involves separating a pulse into its constituent colors, manipulating them individually, and then recombining them to create a new pulse shape. Meanwhile, wavefront shaping techniques enable the spatial structuring of light.

By combining pulse shaping and wavefront shaping, scientists can simultaneously manipulate the temporal and spatial characteristics of light, opening up new possibilities for spatiotemporal applications. This research collaboration involved the Italian Institute of Technology (IIT), Politecnico di Milano, and Técnico Lisboa, with Marco Piccardo leading the team. The potential applications of light springs range from time-resolved microscopy, which can capture the motion of molecules and viruses, to laser-plasma acceleration and free-space optical communications, including those in the atmosphere.

A paradigm shift in spatiotemporal light shaping

In their recent publication in Nature Photonics, Piccardo and his team have introduced a groundbreaking approach to shaping spatiotemporal light. Unlike conventional methods that separate colors along a colorful strip, the researchers utilized a specialized diffraction grating with circular symmetry to create a round rainbow of colors.

You can even try a simplified version of this experiment at home by shining a flashlight on an old CD-ROM and capturing a photo with your phone camera. You will witness a round rainbow effect. Now, replace the flashlight with an ultrashort laser pulse and the CD-ROM with a microstructured diffractive device fabricated in a nanofabrication cleanroom, and you’re halfway through the experiment. The second part involves using advanced holograms to structure the different colors of light into optical vortices resembling corkscrews.

This innovative approach generates a new family of spatiotemporal light beams that possess a twisted and highly customizable light structure, evolving on an ultrafast femtosecond timescale. According to Marco Piccardo, this opens up unprecedented possibilities in photonics, allowing for the design of various spectral and structural components.

Characterizing these new broadband light beams presented challenges that the team overcame by developing a powerful reconstruction technique called hyperspectral holography. This technique, combining holography with Fourier transform spectroscopy, enables the complete tomography of complex space-time structures, facilitating a comprehensive understanding of these beams’ spatiotemporal profiles and their interactions with matter.

The team demonstrated the remarkable control afforded by their space-time shaper by tailoring multiple properties of the light springs. A captivating display showcased two of these springs dancing together in space and time.

Exploring the interesting physics exhibited by these beams, the researchers foresee potential advancements in compact accelerators and plasma-based light sources. By bringing these concepts to the laboratory and combining the advanced space-time beams with intense nonlinear laser-matter interactions, they anticipate significant fundamental and technological implications in laser-plasma physics.

While synthesizing these light springs with complete freedom in the laboratory marks a significant achievement, the next step is to integrate them into laser-plasma experiments. The nanophotonic fabrication capabilities of INESC MN in Lisbon and the expertise of plasma research groups at Técnico Lisboa provide an ideal environment for pursuing this ambitious research, according to Piccardo. The aim is to combine these advanced beams with intense nonlinear laser-matter interactions, potentially leading to groundbreaking advancements in the field.

Source: Técnico Lisboa

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