A New Twist for Materials Science: The Formation of Chiral Structures Using the Angular Momentum of Light

Abstract

and various applications particularly at the microscopic scale. This includes optical trapping and manipulation, [4][5][6] optical telecommunications, [7,8] quantum physics, [9] and "super-resolution" microscopy with a spatial resolution beyond the diffraction limit. [10][11][12] New applications for OAM fields have also been proposed in environmental optics and free-space telecommunication. As an example OAM states can potentially propagate though air turbulence with lower degradation than a conventional Gaussian beam. [13,14] New physical effects include studies such as the rotational Doppler effect originating from interactions of such fields and rotating objects that may provide new technologies for remote sensing of rotating bodies in astrophysics. [15,16] In this area of original physical demonstrations, recent studies have shown that irradiation by such an OAM field can twist materials, such as metal, silicon, azo-polymer, and even a liquid-phase resin with the help of spin angular momentum (SAM) of circularly polarized light with the rotating electric field. This can thus shape helical nano/microstructures. [17][18][19][20][21][22][23][24] Going beyond fundamental aspects, twisted materials created by such OAM fields may provide a new understanding of interactions between optical fields and matter on the subwavelength scale that may reveal new physics, e.g., spin-orbit coupling effects or unconventional optomechanical effects for moving beyond traditional forms of optical manipulation. Furthermore, twisted materials created by such OAM fields, will provide a new understanding of interactions between optical fields and matter on a subwavelength scale. For example, the twisted materials manifest the role of both SAM and OAM of light fields and the coupling of SAM and OAM (so-called spin-orbit coupling) effects. This coupling is key not only for understanding fundamental physics but also for controlling optical material structures.Conventional optical tweezers rely on the field gradients near the diffraction limited focus of a laser beam to hold mesoscopic particles solely with focused light beams. However, the technique often fails to efficiently trap and manipulate particles at the nanoscale because the gradient force scales with the volume of the particle (for a dielectric object) and is proportional to the particle's polarizability. In this domain, advanced materials science and nanofabrication technologies have made remarkable progress in structured devices, e.g., photonic crystals, metamaterials, and metasurfaces. These devices offer novel trapping geometries to enhance the interaction between optical fields and materials at the nanoscale. Furthermore, these devices allow the control of Recent work has shown that irradiation with light possessing orbital angular momentum (OAM) and an associated phase singularity, that is an optical vortex, twists a variety of materials. These include silicon, azo-polymer, and even liquid-phase resins to form various helically structured materials. This article provides...

Optical trapping with structured light: a review

“…254 Moreover, among the diverse optical trapping schemes discussed in this review, in our view, several topics have great potential to find exciting future applications, such as the optical trapping of metal particles [183][184][185][186][187][188][189] and chiral particles, 52,53 vacuum levitation, structured light in waveguides, [255][256][257][258][259] optical binding and other collective motions in structured light fields, 113,185,[260][261][262] quantum optomechanics, 30 and optical trapping for multidisciplinary applications. 32 In the future, besides SLMs and DMDs, more flexible, efficient and much less expensive devices will be developed to produce structured beams, which can help build the next generation of optical trapping technology. Furthermore, acoustic trapping 30 and plasmonic trapping 252 have developed rapidly in recent years, and trapping of nanoparticles with electron beams 263,264 has emerged as well, which can find promising applications in biosciences, biosensors, and engineering as well.…”

“…Thus far, structured light beams with customized phase and amplitude have been successfully applied to drive the optical transport of particles in 3D trajectories by exerting optical forces arising from high intensity and phase gradients. Recently, there are several excellent review articles on this topic, [27][28][29][30][31][32][33] including optical pulling force, 28 optical transport of small particles, 29 optomechanics with levitated particles, 30 acoustic and optical trapping for biomedical research, 31 and so on. 32 More recently, advanced optical manipulation using structured light was reviewed, 33 which focused on the manipulation of transparent dielectric particles.…”

Picosecond optical vortex-induced chiral surface relief in an azo-polymer film

“…[18][19][20][21] Optical vortices carry an annular intensity profile and orbital angular momentum (OAM), characterized by a quantum number l, which associated with its helical wavefront. [22][23][24][25][26] To date, several researchers have reported that irradiation with a continuous-wave visible optical vortex can force the helical mass transport of irradiated azo polymers to form wavefront-sensitive surface relief, i.e., chiral surface relief, facilitated by the spin angular momentum (SAM) of circularly polarized light with a helical electric field. [27][28][29][30][31] An ultrafast laser-induced two-photon-absorption (TPA) process offers the trans-cis photoisomerization of azo polymers with high spatial resolution, which could yield further advanced technologies, such as high-density rewritable data storage.…”

Generation of coupled orbital angular momentum modes from an optical vortex parametric laser source

“…The handedness of the optical vortex is also determined by the sign of the topological charge. The optical vortex has been widely applied in a variety of fields, such as optical trapping and manipulation [6][7][8][9][10][11][12], optical metrology [13][14][15], fiber-based or free-space optical communication [16][17][18][19][20][21][22][23][24], quantum computing [25][26][27], cold atom physics [28][29][30][31][32], astrophysics [33][34][35], and material processing [36,37]. Furthermore, an optical vortex enables the twisting of a variety of materials, such as metals [38][39][40][41], semiconductors [42,43], azopolymers [44][45][46], and even liquid-resin to shape helical nano/microscale structures.…”