Photonic Nanojet Mediated Backaction of Dielectric Microparticles

Abstract

Optical radiation force points to the same direction as the photon flux, while the direction reversal is quite challenging and necessitates special efforts. Herein, we present the observation of a photonic nanojet-mediated backaction of dielectric particles owing to the local heating of solvent molecules inside the nanojet in a purely dielectric system. Such backaction has been verified to be photothermal, without the influence from thermally induced turbulence. Our findings have been theoretically corroborated by statistical analysis on the size-dependent force and speed. In addition to the increase with laser power, the backaction force is a competing effect between the absorption and thermal conductivity of the immersion medium and is also affected by the photothermally raised background temperature. The backaction force exerts on dielectric particles with a broad size range. Since most biological particles are dielectric, with a refractive index greater than that for the surrounding medium, this work could inspire applications in biophotonics, such as cell sorting and classification.

Non-Diffracting Light Wave: Fundamentals and Biomedical Applications

“…This also suggests that the unique features of non-diffracting beams can benefit many applications in biomedical optics. Such field is still developing, as the non-diffracting beams can also be applied in many studies, for instance, to homogeneously induce the photonic nanojet on the dielectric microparticles with enhanced backaction force against the photon flux [163] and to excite the fluorophores in the nonlinear optical microscope for multi-photon or high-harmonic generation. All in all, we anticipate that the non-diffracting beam will continue to contribute to many of the biomedical application researches to overcome the light scattering and large penetration drawbacks.…”

Micro-scale opto-thermo-mechanical actuation in the dry adhesive regime

“…To bypass this challenge, the micro-scale mechanical devices, especially actuators—indispensable in various applications, such as optical communications 2 – 5 , optical displays 6 and molecular cargo 7 , 8 —, nowadays generally exploit membrane architecture to mitigate undesirable surface effects and employ scale-invariant electrostatic force 9 , 10 . Alternatively, they operate in low adhesive environments (e.g., immersed in liquids) using tiny optical force (~pN) 11 – 17 , photoelectric force (~ pN) 17 – 19 or taking advantage of bio-inspired actuation strategy 20 . Realizing micro-scale actuators that can freely walk on two-dimensional dry (non-liquid) surfaces directly against strong resistance from the parallel component of surface force, i.e., friction force (~µN), is challenging 21 .…”

Optical Trapping, Sensing, and Imaging by Photonic Nanojets

“…The nanoscopy surpassed the diffraction limit under white light conditions to obtain optical imaging with 50 nm resolution. This simple and effective method can convert a near-field evanescent wave with high-frequency spatial information into propagation modes [45][46][47], offering the possibility to trap and detect nanoparticles [48][49][50][51], enhance the signal [52][53][54][55], mediate backaction force [56], and improve the performance of optical systems [57,58]. In this article, we will summarize the recent research progress of microsphere lenses, introduce three types of microsphere lenses, focus on the applications of microsphere lenses in optical trapping, sensing, and imaging, and discuss potential application scenarios.…”