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She Studies the Sound of Light

Published: 28 June 2013

Ph.D student Erika Svanström transmits laser pulses into materials and then analyzes the ultrasound that’s created from light interacting with the sample in order to determine the properties of the material. In the future she hopes that her work will help to facilitate diagnosis in the area of biomedicine.

- When light hits and is absorbed by a material the temperature change causes an expansion of the material, which in turn leads to a pressure wave in the form of ultrasound. Using sensitive sensors we can analyze the blast and characterize the material, says Erika Svanström, Ph.D student at the Department of EISLAB.

She has been working for three years at Luleå University of Technology with research in the photo acoustics to develop an analytical model of laser-induced ultrasound, how a short pulse of light is absorbed in the thin layer and provides ultrasound.

Using photo acoustic techniques, one can deduce, thermal properties, how much a material expands by heating, optical properties such as how much light is absorbed, or mechanical properties e.g. how quickly the sound travels in the material.

- Photo acoustics is an exciting research field. It is interesting to see how we can get this information out of the physical world with various sensors which provide data that we later use with different mathematical models.

Measurement instruments are already used today to analyze industrial materials, for diagnostics in biomedicine, for example to look for superficial cancer tumors. The research area is growing and finding new application areas, according to Erika Svanström.

- There are proposals to use photo acoustic paper measurement techniques in the paper industry to examine the quality of paper pulp to analyze its properties and to control the manufacturing process in real-time. It increases efficiency and saves money for the company. I believe that there are many areas in which both the human, economic, and environmental interests may benefit from research in photo acoustics, says Erika.

A possible continuation of her postgraduate work could be to use the model as a basis for reconstruction algorithms that will be able to visualize the measured sample in a virtual environment. The model can also be used for ultrasonic measuring technology in order to device a laser induced ultrasound that will be able to match the material properties of the sample.

- Alexander Graham Bell, whom was accredited the invention of the telephone, reported on the effect in the late 1800’s. The research has developed a lot since then and we know a lot more today. My job demanded very long calculations. I had to split up the expressions to study the mathematics in detail. It was also a challenge to find the right materials to conduct experiments on, but I have been privileged to gain much experience from the work, says Erika Svanström.

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