title: Femtosecond near-field scanning optical microscopy.
abstract: We have developed an instrument for optically measuring carrier dynamics in thin-film materials with approximately 150 nm lateral resolution, approximately 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/AIGaAs 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 approximately 1 microm of the implanted stripes, an effect which could not have been resolved with a far-field system.
authors.affiliation: Swiss Federal Institute of Technology Zurich, Institute of Quantum Electronics. nechay@iqe.phys.ethz.ch
authors.forename: B A
authors.initials: BA
authors.lastname: Nechay
authors.forename: U
authors.initials: U
authors.lastname: Siegner
authors.forename: M
authors.initials: M
authors.lastname: Achermann
authors.forename: F
authors.initials: F
authors.lastname: Morier-Genaud
authors.forename: A
authors.initials: A
authors.lastname: Schertel
authors.forename: U
authors.initials: U
authors.lastname: Keller