Femtosecond near-field scanning optical microscopy |
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Authors: | B A Nechay U Siegner M Achermann F Morier-Genaud A Schertel & U Keller |
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Affiliation: | Swiss Federal Institute of Technology Zurich, Institute of Quantum Electronics, ETH Hönggerberg ? HPT, CH-8093 Zürich, Switzerland,;Micrion GmbH, Kirchenstr. 2, 85622 Feldkirchen, Germany |
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Abstract: | We have developed an instrument for optically measuring carrier dynamics in thin-film materials with ≈150 nm lateral resolution, ≈250 fs temporal resolution and high sensitivity. This is accomplished by combining an ultrafast pump–probe laser spectroscopic technique with a near-field scanning optical microscope. A diffraction-limited pump and near-field probe configuration is used, with a novel detection system that allows for either two-colour or degenerate pump and probe photon energies, permitting greater measurement flexibility than that reported in earlier published work. The capabilities of this instrument are proven through near-field degenerate pump–probe studies of carrier dynamics in GaAs/AlGaAs single quantum well samples locally patterned by focused ion beam (FIB) implantation. We find that lateral carrier diffusion across the nanometre-scale FIB pattern plays a significant role in the decay of the excited carriers within ≈1 μm of the implanted stripes, an effect which could not have been resolved with a far-field system. |
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Keywords: | Near-field optics semiconductors ultrafast spectroscopy |
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