Kasperczyk Mark, Person Steven, Ananias Duarte, Carlos Luis D, Novotny Lukas
Photonics Laboratory, ETH Zürich, 8093 Zürich, Switzerland.
Institute of Optics, University of Rochester, Rochester, New York 14627, USA.
Phys Rev Lett. 2015 Apr 24;114(16):163903. doi: 10.1103/PhysRevLett.114.163903. Epub 2015 Apr 23.
We use the magnetic field distribution of an azimuthally polarized focused laser beam to excite a magnetic dipole transition in Eu^{3+} ions embedded in a Y2O3 nanoparticle. The absence of the electric field at the focus of an azimuthally polarized beam allows us to unambiguously demonstrate that the nanoparticle is excited by the magnetic dipole transition near 527.5 nm. When the laser wavelength is resonant with the magnetic dipole transition, the nanoparticle maps the local magnetic field distribution, whereas when the laser wavelength is resonant with an electric dipole transition, the nanoparticle is sensitive to the local electric field. Hence, by tuning the excitation wavelength, we can selectively excite magnetic or electric dipole transitions through optical fields.
我们利用方位角偏振聚焦激光束的磁场分布来激发嵌入Y2O3纳米颗粒中的Eu3+离子的磁偶极跃迁。方位角偏振光束焦点处不存在电场，这使我们能够明确证明纳米颗粒是由527.5 nm附近的磁偶极跃迁激发的。当激光波长与磁偶极跃迁共振时，纳米颗粒映射局部磁场分布，而当激光波长与电偶极跃迁共振时，纳米颗粒对局部电场敏感。因此，通过调节激发波长，我们可以通过光场选择性地激发磁或电偶极跃迁。
