title: A confocal optical microscope for detection of single impurities in a bulk crystal at cryogenic temperatures.
abstract: A compact sample-scanning confocal optical microscope for detection of single impurities below the surface of a bulk crystal at cryogenic temperatures is described. The sample, lens, and scanners are mounted inside a helium bath cryostat and have a footprint of only 19 × 19 mm. Wide field imaging and confocal imaging using a Blu-ray lens immersed in liquid helium are demonstrated with excitation at 370 nm. A spatial resolution of 300 nm and a detection efficiency of 1.6% were achieved.
authors.affiliation: Department of Physics, Lund University, P.O. Box 118, SE-22100 Lund, Sweden.
authors.forename: Jenny
authors.initials: J
authors.lastname: Karlsson
authors.affiliation: Department of Physics, Lund University, P.O. Box 118, SE-22100 Lund, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Rippe
authors.affiliation: Department of Physics, Lund University, P.O. Box 118, SE-22100 Lund, Sweden.
authors.forename: Stefan
authors.initials: S
authors.lastname: Kröll