Optical Vortices Illumination Enables the Creation of Chiral Nanostructures

Omatsu, Takashige; Miyamoto, Katsuhiko; Morita, Ryuji

doi:10.5772/67073

“…Notably, such helical structures formed by OAM field illumination have also been demonstrated in a bulk copper (Cu), silver (Ag), and gold (Au) thin films, which are well‐known to support surface plasmons. In particular, helical Ag needles formed on a thin film, which are dubbed “chiral plasmonic nanojets.” were successfully demonstrated by Syubaev et al A visible wavelength OAM beam (wavelength: 532 nm, pulse energy: 40–230 nJ, pulse duration: 4 ns, ℓ = ±1) was focused to form an annular spot with a diameter of 2–4 µm onto a sample Ag film (thickness: ≈500 nm), deposited by e‐beam evaporation onto a silica glass substrate.…”

Section: Helical Structuresmentioning

confidence: 98%

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

Omatsu

¹

,

Miyamoto

²

,

Toyoda

³

et al. 2019

Advanced Optical Materials

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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...

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“…In summary, the optical radiation force and its deflection angle are constant with respect to for the Gaussian beam and 6-beam interference pattern, while they are non-uniform for the 4-beam interference pattern due to the presence of undulation. Considering past successes in chiral structure formation using Gaussian beams 5 , 23 , 24 , it can be hypothesised; given a vector with the centre of the light spot at and polar coordinates , and an optical radiation force vector at , the deflection angle and must be constant with respect to for the chiral structure to form. Next, we investigate the difference based on the experimental results with interference patterns.…”

Section: Theorymentioning

confidence: 99%

Simulation of optical radiation force distribution in interference patterns and necessary conditions for chiral structure formation on dielectrics

Nakata

¹

,

Tsubakimoto

²

,

Shiraga

³

et al. 2022

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A chiral structure is formed by the optical radiation force induced by a circularly polarized light that has spin angular momentum; chiral structures are expected to be used for light control devices and molecular chirality discrimination devices. In this paper, we clarify the relationship between the differences in the distributions of the optical radiation force and the possibility of formation of chiral structures. We first simulate the optical radiation force distribution in the case of a Gaussian beam that successfully forms a chiral structure. Given a vector $${\varvec{r}}$$ r with a centre of the light spot $$\mathrm{O}$$ O and polar coordinates $$R(\left|{\varvec{r}}\right|, \theta )$$ R ( r , θ ) , and an optical radiation force vector $${\varvec{F}}$$ F at $$R$$ R , the angle $${\theta }^{\mathrm{^{\prime}}}=\mathrm{\angle }({\varvec{r}}, {\varvec{F}})$$ θ ′ = ∠ ( r , F ) and $$\left|{\varvec{F}}\right|$$ F must be constant with respect to the declination angle $$\theta$$ θ for a chiral structure to form. These conditions are fulfilled in the case of a 6-beam interference pattern, but not in the case of a 4-beam interference pattern, which is consistent with the result that no chiral structure is formed in the latter case. The equations derived for simulation of optical radiation force distribution can be used for any optical intensity distribution, and will be of great help in the research of any dielectrics deformation.

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“…[23][24][25] This total AM has been experimentally observed in studies of optically trapped microparticles exhibiting orbital and spinning motion depending on the orbital and spin AM of the trapping beam. [26][27][28] Separately, a pulsed orbital AM field has enabled the formation of nano-/microscale "twisted" needle-like structures (so-called twisted needles) on the surface of irradiated bulk tantalum (Ta), silicon (Si), copper (Cu) and silver (Ag), and gold (Au) thin films [16][17][18][19][20][21][22]29,30 (Fig. 1).…”

mentioning

confidence: 99%

“…(a) Ta substrate. 16 (b)-(d) Ag film, 20 (e), (f) Si substrate, 21 (g), (h) Cu needles, 29 and (i) Au thin film. 30 Reproduced with permission.…”

mentioning

confidence: 99%

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Twisted mass transport enabled by the angular momentum of light

Omatsu

¹

,

Masuda

²

,

Miyamoto

³

et al. 2020

J. Nanophoton.

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Light may carry both orbital angular momentum (AM) and spin AM. The former is a consequence of its helical wavefront, and the latter is a result of its rotating transverse electric field. Intriguingly, the light-matter interaction with such fields shows that the orbital AM of light causes a physical "twist" in a range of materials, including metal, silicon, azopolymer, and even liquid-phase resin. This process may be aided by the light's spin AM, resulting in the formation of various helical structures. The exchange between the AM of light and matter offers not only unique helical structures at the nanoscale but also entirely novel fundamental phenomena with regard to the light-matter interaction. This will lead to the future development of advanced photonics devices, including metamaterials for highly sensitive detectors as well as reactions for chiral chemical composites. Here, we focus on interactions between the AM of light and azopolymers, which exhibit some of the most diverse structures and phenomena observed. These studies result in helical surface relief structures in azopolymers and will leverage next-generation applications with light fields carrying optical AM.

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Optical Vortices Illumination Enables the Creation of Chiral Nanostructures

Cited by 7 publications

References 60 publications

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

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

Simulation of optical radiation force distribution in interference patterns and necessary conditions for chiral structure formation on dielectrics

Twisted mass transport enabled by the angular momentum of light

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