Skip to main content
. Author manuscript; available in PMC: 2018 Apr 3.
Published in final edited form as: Optica. 2017 Nov 20;4(11):1337–1343. doi: 10.1364/OPTICA.4.001337

Fig. 3.

Fig. 3

Magnetic-particle-guided optical focusing with the frequency modulation method. The electromagnets were driven by 25 Hz rectangular waves. Images were captured with the setup shown in Fig. 2(b). The focus achieved when the reference beam frequency was shifted by (a) 25 Hz (fundamental frequency), (b) 50 Hz (second harmonic), and (c) 75 Hz (third harmonic) relative to the laser frequency. (d) Control experiment: no focus was observed when the reference beam frequency was shifted by 30 Hz (frequency mismatch). Scale bar, 5 µm.