Optical levitation of nanodiamonds by doughnut beams in vacuum

Abstract

Optically levitated nanodiamonds with nitrogen-vacancy centers promise a high-quality hybrid spinoptomechanical system. However, the trapped nanodiamond absorbs energy form laser beams and causes thermal damage in vacuum. It is proposed here to solve the problem by trapping a composite particle (a nanodiamond core coated with a less absorptive silica shell) at the center of strongly focused doughnut-shaped laser beams. Systematical study on the trapping stability, heat absorption, and oscillation frequency concludes that the azimuthally polarized Gaussian beam and the linearly polarized Laguerre-Gaussian beam LG 03 are the optimal choices. With our proposal, particles with strong absorption coefficients can be trapped without obvious heating and, thus, the spin-optomechanical system based on levitated nanodiamonds are made possible in high vacuum with the present experimental techniques.Introduction-. By trapping, detecting and manipulating nano-and micro-particles [1], optical tweezers are widely used in biophysics [2-4], colloidal sciences [5], chemistry, microfluidic dynamics [6], and fundamental physics [7][8][9][10][11][12][13][14][15]. Because of the wide applicability and high tunablity of the optically levitated systems, several schemes [16] were proposed to realize the ground-state cooling [17], to search for non-Newtonian gravity [18] and to detect gravitational wave [19]. Particularly, it brings about more interesting phenomena and novel applications [20,21] when the trapped particles have internal degrees of freedom (such as spins or electric dipoles) and enter the quantum regime.Optically levitated nanodiamonds with nitrogen-vacancy (NV) centers [22][23][24][25][26] are one of the most promising candidates for implementing a spin-optomechanical hybrid system. In principle, this system can have both long spin coherence time and high quality factor of mechanical oscillation in vacuum. The electron spins of NV centers were shown to have long spin coherence time (in the order of 10 2 µs) even in nanodiamonds of diameter about 20 nm [27]. When trapped in high-vacuum, the dielectric particles are predicted to have ultra-high quality factor Q larger than 10 10 [16,18,28]. Researchers have trapped diamond particles and observed the signal from NV centers in liquid [29,30], in air [31] and very recently in vacuum with pressure down to ∼ kPa [24,25] and ∼ 100 Pa [26].Realizing high quality mechanical oscillation requires trapping the particles in high vacuum (e.g, 10 −6 Pa) to get Q ∼ 10 10 . However, the high-vacuum condition usually causes the thermal damage problem, and experimentally trapping a nanodiamond in high vacuum is still very challenging. Nanodiamonds will absorb energy from the trapping laser beams due to the intrinsic defects [26] and the inevitable imperfections or graphitization [32] on diamond surface. The absorbed energy can hardly be dissipated in a high-vacuum environment, and the nanodiamonds will be quickly heated up significantly [24][25][26], which is unfavorable to the defect centers...

Optomechanics with levitated particles

“…There is, in principle, no limit to the value of the topological charge, and as of now the record value is 10,010 quanta [202]. OAM beams often have interesting intensity profiles, such as doughnut beams, which may be useful to avoid optical absorption and heating [203]. Transfer of OAM does not require a polarization anisotropy, rather the c.o.m.…”

“…of a particle undergoes a (potentially complex) orbit. This has only recently been observed for particles levitated under vacuum conditions [203][204][205]. The rotation rate increases with increasing topological charge, but at high topological charge the motion may become extremely complex, and potentially unstable [47; 205].…”

Fano Resonance in Artificial Photonic Molecules

“…So, various systems, including optical cavities, [ 36–39 ] nanoclusters, [ 40–43 ] photonic crystals, [ 44–45 ] gratings, [ 46–49 ] metamaterials, [ 50–53 ] metasurfaces, [ 54–57 ] and many others, [ 58–63 ] have been proposed theoretically and observed experimentally to exhibit Fano resonance. Inspired by recent progress in numerous novel materials, [ 64–69 ] including 2D materials with exotic optoelectronic properties, [ 70–72 ] superconducting materials, [ 73,74 ] phase‐changed materials, [ 75,76 ] low loss dielectric materials [ 77,78 ] and quantum dots, [ 79–82 ] many opportunities to investigate Fano resonance are anticipated.…”

Radiation forces study of a Laguerre Gaussian beam type TEM∗01 on a dielectric sphere in the Rayleigh scattering regime

“…Currently, the use of optical vortex trapping beams has been increasing and many applications have been found [5][6][7][8][9]. Compared to regular Gaussian beams, doughnut-shaped modes, such as TEM 01 * , are suitable to avoid laser-induced heating and optical damage since the intensity profile drops to zero at the optical axis [6,9].…”