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Content

• Background
• Development of Attosecond Pulses
• Applications of attosecond physics

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Quick Summary:

Anne L’Huillier, Pierre Agostini and Ferenc Krausz have been awarded Nobel Prize in Physics, 2023.

What did they do?

• Through their experiments, they have created flashes of light that are short enough to take snapshots of electrons’ extremely rapid movements.
• Anne L’Huillier discovered a new effect from laser light’s interaction with atoms in a gas.
• Pierre Agostini and Ferenc Krausz demonstrated that this effect can be used to create shorter pulses of light than were previously possible.

Background: Understanding the Problem:

Human eyes cannot clearly see hummingbird’s beating its wings which can be around 80 times per second. We are only able to perceive this as a whirring sound and blurred movement. It is because extremely short events are impossible to observe by human eyes.

High Speed photography can capture detailed images of fleeting (short) phenomena. A highly focused photograph of a hummingbird in flight requires an exposure time that is much shorter than a single wingbeat.

The faster the event, the faster the picture needs to be taken if it is to capture the instant.

Atom’s natural timescale is that of femtoseconds (10-15 sec). These movements can be studied with the very shortest pulses that can be produced with a laser.

• A femtosecond was, in the 1980s, regarded as the limit for the flashes of light it was possible to produce.

But, electrons natural timescale is further lower in attoseconds (10-18 sec) i.e. in the world of electrons, positions and energies change at speeds of between one and a few hundred attoseconds. Therefore, flashes of light produced at femtosecond was not enough to see processes occurring on the timescale of electrons.

Development of Attosecond Pulses:

• The mathematics that describes waves demonstrate that any wave form can be built if enough waves of the right sizes, wavelengths, and amplitudes (distance between peaks and troughs) are used. The trick to attosecond pulses is that it is possible to make shorter pulses by combining more and shorter wavelengths.
• In 1987, Anne L’ Huillier and her colleagues at a French laboratory passed an infrared laser beam through a noble gas. The beam’s interaction with atoms in the gas produced overtones (overtones are waves of light whose wavelength was an integer fraction of the beam. For e.g, if the beam had a wavelength of 100, the overtones would have wavelength of 10, 25, 50 etc.)
  • By finetuning the setup used to produce the overtones, scientists realized that it should be possible to create intense pulses of light each a few attosecond long.
• In 2001, Pierre Agostini and his research group in France successfully produced and investigated a series of 250-attosecond light pulses, or a pulse train.
• At the same time, Ferenc Krausz and his team in Australia developed a technique to separate an individual 650 second pulse from a pulse train.
  • Using this researcher were able to measure the energy of some electrons released by some krypton atoms.

Applications of attosecond physics:

• It allows scientists to capture images of activities that happen in incredible short spans. This can be used for exploring short-lived atomic and molecular processes implicated in fields like material, science, electronics, and catalysis.
• In medical diagnostics, attosecond pulses can be used to check for the presence of certain molecules based on their fleeting signatures.
• These pulses could also be used to develop faster electronic devices, and better telecommunication, imaging and spectroscopy.