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We use ultrafast optical techniques to study highly non-equilibrium electron and lattice dynamics in semiconductors and metals — materials that are important for electronic and optoelectronic devices. Because of their miniaturization, electronic and optoelectronic devices operate increasingly in a regime of extremely high carrier density. We excite a very high number of electrons in a material by an intense optical pulse with a duration of less than a hundred femtoseconds. This allows us to create exotic states of matter that contain excited electronic populations 3 to 4 orders of magnitude larger compared to weak excitation studies.
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Broad band probe of the dielectric function |
Ripples in the dielectric function of tellurium |
We developed a unique time-resolved, broad-band dual angle reflectometry technique, that allows us to probe the real and imaginary parts of the dielectric function of a solid as it evolves in response to the optical excitation. Our setup has a time resolution of 20 fs and a broadband frequency range extending from the near infrared to the near ultraviolet. Recently, we directly observed an ultrafast semiconductor to metal phase transition in gallium arsenide and demonstrated all-optical control of the lattice configuration of highly excited tellurium via optical phonon excitation.
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| Plainly Speaking | The miniaturization of electronic devices pushes the operation of these devices to increasingly higher speed and higher temperatures. We use very short pulses of light to create extreme conditions in electronic materials and use a second short laser pulse to probe how the fundamental properties of the materials are changing.
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Measuring electronic properties at light speed
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With a better understanding of materials we hope to develop the means to tailor their properties according to the needs of technology.
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