Fig. 1. Classification of the optical force models

Fig. 2. Schematic diagram of the optical tweezers in vacuum. (a) Single-beam optical tweezers; (b) dual-beam optical tweezers

Fig. 3. Schematic diagram of the single-beam optical tweezers system with vertical upward^[66]

Fig. 4. Schematic diagram of the single-beam optical tweezers system with a parabolic mirror^[67]

Fig. 5. Influence of the misalignment distance d in the double-beam optical tweezers on the behavior of capturing microspheres. (a) When d=0, the microsphere is stably captured at the center of the optical tweezers; (b) when 0<d<d₁, the microsphere spirals to the center; (c) when d≥d₁, the microsphere rotates around the center^[36]

Fig. 6. Principle diagram of the integrated optical tweezers. (a) Cross-section of the waveguide; (b) image of the waveguide cross-section by scanning electron microscopy; (c) spot pattern in the waveguide; (d) top view of optical tweezers using waveguides when coupling red light; (e) microscopic view of optical tweezers using waveguides^[69]

Fig. 7. Schematic diagram of the particle loading structure by piezoelectric ceramics^[71]

Fig. 8. Schematic diagram of the single-microsphere launching by pulsed lasers^[72]

Fig. 9. Principle diagram of the back focal plane displacement measurement^[80]

Fig. 10. Displacement measurement using lateral scattered laser on back focal plane^[39]

Fig. 11. Schematic diagram of the displacement detection by balanced detectors^[16]

Fig. 12. Principles of back-light interference displacement measurement method^[83]

Fig. 13. Basic process of optical tweezers feedback control

Fig. 14. Principle of the optical momentum feedback^[16]

Fig. 15. Schematic diagram of the parameter feedback scheme^[17]

Fig. 16. Diagram of the feedback cooling scheme by electrostatic forces^[19]

Fig. 17. Diagram of the cavity feedback cooling scheme. (a) Light path of the feedback cooling scheme; (b) light transmission^[16]

Fig. 18. Schematic diagram of the self-feedback intracavity optical tweezers. (a) Intracavity optical tweezers without trapped particles; (b) when trapped particles are located in the center of optical tweezers; (c) when trapped particles are offset from the center of optical tweezers ^[86]

Fig. 19. Quality factors of the different resonance subsystems^[32]

Fig. 20. Sensing system of the vacuum optical tweezers. (a) Experimental device; (b) optical tweezers force corresponding to axial offset; (c) time series curve of axial displacement of captured particles^[30]

Fig. 21. Diagram of the optical tweezers system in vacuum for acceleration sensing applications^[90]

Fig. 22. Rapid spinning of the nanoparticles suspended by a circularly polarized laser beam in optical tweezers in vacuum. (a) Experimental setup; (b) relationship curves between the rotation rate of the captured particles and the ambient air pressure^[94]

Fig. 23. Responses of the trapped microsphere in the electric field due to residual charges^[66]