How a Long Laser Pulse Was Squeezed into an Ultrafast Lightning Bolt

Original: "Sub-2-Cycle, Terawatt Pulses via Double-Stage Multi-Pass Cell Compression of an Yb Laser"

· Victor Koltalo, Jaismeen Kaur, Louis Daniault, Antoine Cavagna, Mickael Allemand, Florent Pallas, Antoine Courjaud, Emilien Gontier, Cédric Sire, François Sylla, Rodrigo Lopez-Martens

arXiv:2609.04989v1 · 2026-09-04 · CC BY 4.0 · 1 min

Optics

Send light through gas twice, and it becomes 65 times shorter and hundreds of times more powerful.

When a blacksmith works the bellows, air comes out in a strong jet. You can do something similar with light: take a long laser pulse and compress it so it becomes shorter and more powerful. Scientists in France compressed an ytterbium laser pulse by a factor of 65. It went from 400 femtoseconds down to 6.2 femtoseconds, and its power climbed to 1.4 terawatts.

In 6.2 femtoseconds, light travels just 1.86 micrometers. That is less than the thickness of a human hair.

How does it work? First, the laser beam is sent through a chamber filled with argon many times. The gas broadens the light's spectrum, adding new colors. Then special mirrors align those colors, and the pulse gets compressed. The same trick is repeated once more with helium. Very little energy is lost: at the end, 12.5 millijoules remain out of the original 18.

Such a short, powerful pulse is needed to accelerate electrons in plasma. Conventional accelerators are huge, but a laser-based one can fit on a tabletop. That could prove useful in medicine and in testing materials for strength.

Whole graph →

A pulse of 6.2 femtoseconds is so short that light travels only 1.86 micrometers during it, less than the thickness of a human hair.

a_0 = 0.85 \sqrt{I[10^{18} \text{ Вт/см}^2] \lambda^2[\text{мкм}]}

Dimensionless amplitude of the laser field, determining the regime of interaction with plasma; for a0 > 1 electrons become relativistic.

C = 0.59B + 1

Empirical formula relating the compression factor C to the accumulated nonlinear phase shift B; for C=65, B≈100 rad is required.

Concepts

ultrashort pulse attosecond laser laser power

I am the author

How a Long Laser Pulse Was Squeezed into an Ultrafast Lightning Bolt