Degree of Excellence in the Interaction of Light with Matter

Degree of Excellence in the Interaction of Light with Matter
Degree of Excellence in the Interaction of Light with Matter - Mina Bionta/SLAC

It explores how oscillations of light interact with matter, capturing snapshots of interactions on a time scale. Mina Bionta has not always been interested in physics, despite living with two other physicists. As a child he experimented with different sciences to carve his own path, but by the time he graduated from high school she had changed her mind about becoming a physicist. After completing several summer internships at various laboratories, Bionta continued her studies in physics at the university level. Asking professors, “Will they hire me?” She states that cold e-mailing to ask gives her plenty of opportunities. The SLAC National Accelerator Laboratory in California was one of these opportunities.

The world's first x-ray free electron laser, the Linac Coherent Light Source (LCLS), was newly operational in 2009, and Bionta spent his internship synchronizing with optical lasers to get the system ready to take snapshots of atoms and molecules at ultrafast timescales.

Bionta holds a PhD in ultrafast laser-induced emission of electrons from metallic nanostructures, as he was very impressed with the light-matter interaction research enabled by SLAC's x-ray laser. Since then, people have been taking advantage of these rapid emissions to learn more about how light interacts with various materials. spectroscopic instruments it creates. Bionta completed her postdoctoral fellowship at the Massachusetts Institute of Technology in August and will rejoin SLAC as a staff scientist in October. He wants to create new techniques for observing how X-ray and visible light pulses interact with matter there. Bionta discussed his passion for lasers and ultrafast optics research with Physics Magazine. Let me give you a summary of this short interview.

What is your favorite aspect of using the laser?

I'm fascinated by the fact that a wide variety of events, including phase transitions, nonlinear behavior, and chemical reactions, can result from a laser coming into contact with a material. The interactions between light and matter are also extremely clean, because light only supplies matter with energy, and scientists can precisely control how much energy goes into the system by adjusting a few key parameters, such as the hue of the light.

What laser issue are you currently dealing with?

I'm working with my team on a small device that can track the pattern of ultra-fast laser pulses before and after they come into contact with a laser-conducting material. This technique will allow us to study how these pulses interact with a material without damaging it, for example, how it transmits energy to a photovoltaic film.

Why is it vital to measure these interactions?

Understanding the electrical and atomic properties of a material depends on it. There are two methods for measuring interactions between light and matter. As one method, the absorption spectrum of light after interacting with a substance can be measured.

However, this strategy has a downside: if the interaction results in a phenomenon with extremely fast dynamics, such as a chemical reaction, the sharp peaks in the absorption spectrum expected from various material components may instead coalesce into a single, disturbing bump.

The alternative method is to measure the waveform of light over time to directly determine the phase and amplitude of light before and after it interacts with a substance. These measurements are difficult because they require a measurement approach with very precise time resolution. However, we can achieve this accuracy by causing the emission of incredibly fast electron bursts.

How do you do this?

In a clever way involving nanometer-sized antennas. These nanoantennas are the building blocks of our microprocessor-sized device. The electric field of the incoming light will be amplified by the antennas, thanks to their well thought-out form. The device is placed on or next to an interesting item. The device reads data on how the ultra-fast pulsed laser interacts with the sample after stimulating the material.

The field at the tip of a nanoantenna becomes so intense when a laser pulse penetrates it, causing the tip to discharge a burst of electrons. When you send several laser pulses to a tip, the result is a quick succession of short but powerful bursts of electrons, each containing data about the light entering the tip.

The time resolution of the bursts is less than a femtosecond, or half a cycle of the illuminating laser pulse, for our tests. So, by tracking these bursts, we can probe light-matter interactions with fast time resolution.

How exactly do you track the explosions?

Nanoantennas release a burst of electrons in response to each incoming laser pulse. Each of these electron bursts is picked up by a nanowire placed perpendicular to the antenna array. The electric field of the laser drives a current, which is also carried by the nanowire. As a result of the interaction between the nanowire and the electron burst, the intensity of the current changes, providing us with time-dependent information about the light waveform. We plot these final changes on an external detector.

Why is this information important to scientists?

To observe how light-dependent processes happen very quickly. For example, plant scientists can use our method to investigate how energy is transferred from sunlight to plant cells. However, the method is not limited to biological samples. It is used for gas detection, drug discovery, food safety, photovoltaics and medicine. This tool can be used to investigate nonlinear condensed matter processes such as high harmonic generation, exciton dynamics in photovoltaic systems, and spectroscopic signatures of certain molecules.

Source: physics.aps.org/

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