title: Spectroscopy of single Pr3+ ion in LaF3 crystal at 1.5 K.
abstract: Optical read-out and manipulation of the nuclear spin state of single rare-earth ions doped in a crystal enable the large-scale storage and the transport of quantum information. Here, we report the photo-luminescence excitation spectroscopy results of single Pr(3+) ions in a bulk crystal of LaF3 at 1.5 K. In a bulk sample, the signal from a single ion at the focus is often hidden under the background signal originating from numerous out-of-focus ions in the entire sample. To combine with a homemade cryogenic confocal microscope, we developed a reflecting objective that works in superfluid helium with a numerical aperture of 0.99, which increases the signal by increasing the solid angle of collection to 1.16π and reduces the background by decreasing the focal volume. The photo-luminescence excitation spectrum of single Pr(3+) was measured at a wing of the spectral line of the (3)H4 → (3)P0 transition at 627.33 THz (477.89 nm). The spectrum of individual Pr(3+) ions appears on top of the background of 60 cps as isolated peaks with intensities of 20-30 cps and full-width at half-maximum widths of approximately 3 MHz at an excitation intensity of 80 W cm(-2).
authors.affiliation: Department of Physics, Tokyo Institute of Technology, Ookayama 2-12-1 Meguro Tokyo, 152-8550 Japan.
authors.forename: Ippei
authors.initials: I
authors.lastname: Nakamura
authors.affiliation: Department of Physics, Tokyo Institute of Technology, Ookayama 2-12-1 Meguro Tokyo, 152-8550 Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Yoshihiro
authors.affiliation: Department of Physics, Tokyo Institute of Technology, Ookayama 2-12-1 Meguro Tokyo, 152-8550 Japan.
authors.forename: Hironori
authors.initials: H
authors.lastname: Inagawa
authors.affiliation: Department of Physics, Tokyo Institute of Technology, Ookayama 2-12-1 Meguro Tokyo, 152-8550 Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Fujiyoshi
authors.affiliation: Department of Physics, Tokyo Institute of Technology, Ookayama 2-12-1 Meguro Tokyo, 152-8550 Japan.
authors.forename: Michio
authors.initials: M
authors.lastname: Matsushita