Abstract
Optical trapping is an indispensable tool in physics and the life sciences. However, there is a clear trade off between the size of a particle to be trapped, its spatial confinement, and the intensities required. This is due to the decrease in optical response of smaller particles and the diffraction limit that governs the spatial variation of optical fields. It is thus highly desirable to find techniques that surpass these bounds. Recently, a number of experiments using nanophotonic cavities have observed a qualitatively different trapping mechanism described as ‘self-induced back-action trapping’ (SIBA). In these systems, the particle motion couples to the resonance frequency of the cavity, which results in a strong interplay between the intra-cavity field intensity and the forces exerted. Here, we provide a theoretical description that for the first time captures the remarkable range of consequences. In particular, we show that SIBA can be exploited to yield dynamic reshaping of trap potentials, strongly sub-wavelength trap features, and significant reduction of intensities seen by the particle, which should have important implications for future trapping technologies.
Highlights
InroductionOptical trapping is one of the most important experimental tools in physics and life sciences because it enables precise control over small dielectric particles [1]
Interplay between the intra-cavity field intensity and the forces exerted
We show how parameters can be chosen to maximize the effects of back-action, and that a single ‘back-action parameter’ h μ Q V, Vm proportional to the resonator quality factor and the ratio of particle to cavity mode volumes, characterizes the performance of any optimized system
Summary
Optical trapping is one of the most important experimental tools in physics and life sciences because it enables precise control over small dielectric particles [1]. The difficulty of trapping a particle generally increases with decreasing size, due to the decreased optical response of the particle This requires a commensurate increase in field intensity to maintain trap stability, and leads to associated problems such as thermal or material damage. The key physics is that the position of the trapped particle alters the resonance frequency This results in a ‘self-induced back-action’ (SIBA) effect in which the motion dynamically affects the build up of intra-cavity intensity, and the optical force exerted. Large shifts in the cavity detuning relative to the laser frequency as the particle moves can induce strong changes in the intra-cavity intensity Under these circumstances, and when properly optimized, such a trap yields very different trade-offs between intensities, trap depth, and confinement, which should have significant consequences for optical trapping technology. We discuss the possibilities for implementation in nano-plasmonic (figure 1(b)) and photonic crystal (figure 1(c)) systems
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
