Direct detection of photoinduced magnetic force at the nanoscale reveals magnetic nearfield of structured light

Abstract

We demonstrate experimentally the detection of magnetic force at optical frequencies, defined as the dipolar Lorentz force exerted on a photoinduced magnetic dipole excited by the magnetic component of light. Historically, this magnetic force has been considered elusive since, at optical frequencies, magnetic effects are usually overshadowed by the interaction of the electric component of light, making it difficult to recognize the direct magnetic force from the dominant electric forces. To overcome this challenge, we develop a photoinduced magnetic force characterization method that exploits a magnetic nanoprobe under structured light illumination. This approach enables the direct detection of the magnetic force, revealing the magnetic nearfield distribution at the nanoscale, while maximally suppressing its electric counterpart. The proposed method opens up new avenues for nanoscopy based on optical magnetic contrast, offering a research tool for all-optical spin control and optomagnetic manipulation of matter at the nanoscale.

Optical Forces on Multipoles Induced by the Belinfante Spin Momentum

“…We envision that the family of multipolar BSM forces here demonstrated, which comprises information about high-order derivatives of the local BSM, would also be exploited for developing advanced photon-induced microscopy for field measurements and topographic reconstruction. [8,52,53]…”

Surface-phonon-polariton-enhanced photoinduced dipole force for nanoscale infrared imaging

“…the dipole force, on the tip [ 22 ]. Additionally, by incorporating a resonant nanostructure and employing structured light illumination, the tip can also be polarized as an exclusive magnetic dipole, enabling the direct detection of the magnetic dipole force [ 23 ]. Therefore, the PiDF is expected to show significantly localized multidimensional electromagnetic responses compared to those of the PiTF, so that imaging with PiDF could yield information far beyond the scope of PiTF, such as sample-tip distance, localized refractive index differences, and various types of subtle electric and magnetic near-field properties.…”

Nanoscopic visualization of chiro-optical field in photoinduced force microscopy

“…As a nanoscopic chiro-optical measurement method, utilization of optical force is promising [4][5][6]. For the optical force measurements based on a scanning probe, photoinduced force microscopy (PiFM), has been developed and extensively investigated recently [7][8][9][10][11]. In PiFM, both the tip and the sample are irradiated by polarized light, and the nanoscopic optical responses of matters are observed via the motion of the tip induced by the incident light.…”