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Sensitive vectorial optomechanical footprint of light in soft condensed matter


Among the properties of light that dictate its mechanical effects, polarization has held a special place since the mechanical identification of the photon spin1. Nowadays, little surprise might be expected from the mechanical action of linearly polarized weakly focused (paraxial) beams on transparent and homogeneous dielectrics. Still, here we unveil vectorial optomechanical effects mediated by the material anisotropy and the longitudinal field component inherent to real-world beams2,3. Experimentally, this is demonstrated by using an elastic anisotropic medium prone to exhibit a sensitive and reversible effect, that is, a nematic liquid crystal, and our results are generalized to vector beams4. This represents an alternative to irreversible damaging approaches restricted to strongly non-paraxial fields5. The reported creation of multiple self-induced lenses from a single beam also open up topology assisted all-optical information routing strategies. Moreover, our findings point out the transverse internal optical energy flows (spin and orbital)6 as novel triggers to tailor structured optical nonlinearities.

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Fig. 1: Vectorial optomechanics from a linearly polarized Gaussian beam.
Fig. 2: Vectorial optical structuring experiment under linearly polarized Gaussian beam.
Fig. 3: Vectorial control of vectorial optical structuring.
Fig. 4: Wavefront curvature enabled vectorial optomechanics.

Data availability

The data that support the findings of this study are available on request from the corresponding author.


  1. 1.

    Beth, R. A. Mechanical detection and measurement of the angular momentum of light. Phys. Rev. 50, 115–125 (1936).

    ADS  Google Scholar 

  2. 2.

    Lax, M., Louisell, W. H. & McKnight, W. B. From Maxwell to paraxial wave optics. Phys. Rev. A 11, 1365–1370 (1975).

    ADS  Google Scholar 

  3. 3.

    Ciattoni, A., Crosignani, B. & Di Porto, P. Vectorial theory of propagation in uniaxially anisotropic media. J. Opt. Soc. Am. A 18, 1656–1661 (2001).

    ADS  Google Scholar 

  4. 4.

    Rosales-Guzmán, C., Ndagano, B. & Forbes, A. A review of complex vector light fields and their applications. J. Opt. 20, 123001 (2018).

    ADS  Google Scholar 

  5. 5.

    Hnatovsky, C., Shvedov, V., Krolikowski, W. & Rode, A. Revealing local field structure of focused ultrashort pulses. Phys. Rev. Lett. 106, 123901 (2011).

    ADS  Google Scholar 

  6. 6.

    Bekshaev, A., Bliokh, K. Y. & Soskin, M. Internal flows and energy circulation in light beams. J. Opt. 13, 053001 (2011).

    ADS  Google Scholar 

  7. 7.

    Blume, H., Bader, T. & Luty, F. Bi-directional holographic information storage based on the optical reorientation of FA centers in KCl:Na. Opt. Commun. 12, 147–151 (1974).

    ADS  Google Scholar 

  8. 8.

    Wong, G. K. & Shen, Y. Optical-field-induced ordering in the isotropic phase of a nematic liquid crystal. Phys. Rev. Lett. 30, 895 (1973).

    ADS  Google Scholar 

  9. 9.

    Zolot’ko, A. S., Kitaeva, V. F., Kroo, N., Sobolev, N. N. & Csillag, L. The effect of an optical field on the nematic phase of the liquid crystal ocbp. JETP Lett. 32, 158–161 (1980).

    ADS  Google Scholar 

  10. 10.

    Kim, W. & Felker, P. M. Spectroscopy of pendular states in optical-field-aligned species. J. Chem. Phys. 104, 1147–1150 (1996).

    ADS  Google Scholar 

  11. 11.

    Sakai, H. et al. Controlling the alignment of neutral molecules by a strong laser field. J. Chem. Phys. 110, 10235–10238 (1999).

    ADS  Google Scholar 

  12. 12.

    Friese, M. E. J., Nieminen, T. A., Heckenberg, N. R. & Rubinsztein-Dunlop, H. Optical alignment and spinning of laser-trapped microscopic particles. Nature 394, 348–350 (1998).

    ADS  Google Scholar 

  13. 13.

    Higurashi, E., Sawada, R. & Ito, T. Optically induced angular alignment of trapped birefringent micro-objects by linearly polarized light. Phys. Rev. E 59, 3676 (1999).

    ADS  Google Scholar 

  14. 14.

    Tong, L., Miljkovic, V. D. & Kall, M. Alignment, rotation, and spinning of single plasmonic nanoparticles and nanowires using polarization dependent optical forces. Nano Lett. 10, 268–273 (2010).

    ADS  Google Scholar 

  15. 15.

    Liu, M., Zentgraf, T., Liu, Y., Bartal, G. & Zhang, X. Light-driven nanoscale plasmonic motors. Nat. Nanotechnol. 5, 570–573 (2010).

    ADS  Google Scholar 

  16. 16.

    Ciattoni, A., Cincotti, G. & Palma, C. Propagation of cylindrically symmetric fields in uniaxial crystals. J. Opt. Soc. Am. A 19, 792–796 (2002).

    ADS  MATH  Google Scholar 

  17. 17.

    Khoo, I. C. Nonlinear optics of liquid crystalline materials. Phys. Rep. 471, 221–267 (2009).

    ADS  Google Scholar 

  18. 18.

    Freund, I. Polarization singularity indices in gaussian laser beams. Opt. Commun. 201, 251–270 (2002).

    ADS  Google Scholar 

  19. 19.

    Santamato, E. & Shen, Y. Field-curvature effect on the diffraction ring pattern of a laser beam dressed by spatial self-phase modulation in a nematic film. Opt. Lett. 9, 564–566 (1984).

    ADS  Google Scholar 

  20. 20.

    Lucchetti, L., Suchand, S. & Simoni, F. Fine structure in spatial self-phase modulation patterns: at a glance determination of the sign of optical nonlinearity in highly nonlinear films. J. Opt. A 11, 034002 (2009).

    ADS  Google Scholar 

  21. 21.

    Lucchetti, L., Criante, L., Bracalente, F., Aieta, F. & Simoni, F. Optical trapping induced by reorientational nonlocal effects in nematic liquid crystals. Phys. Rev. E 84, 021702 (2011).

    ADS  Google Scholar 

  22. 22.

    Zel’dovich, B. Y., Tabiryan, N. V. & Chilingaryan, Y. S. Fredericks transitions induced by light fields. Sov. Phys. JETP 54, 32–37 (1981).

    Google Scholar 

  23. 23.

    Durbin, S., Arakelian, S. & Shen, Y. Optical-field-induced birefringence and freedericksz transition in a nematic liquid crystal. Phys. Rev. Lett. 47, 1411 (1981).

    ADS  Google Scholar 

  24. 24.

    Porenta, T., Ravnik, M. & Zumer, S. Complex field-stabilised nematic defect structures in Laguerre–Gaussian optical tweezers. Soft Matter 8, 1865–1870 (2012).

    ADS  Google Scholar 

  25. 25.

    Otte, E., Tekce, K. & Denz, C. Tailored intensity landscapes by tight focusing of singular vector beams. Opt. Express 25, 20194–20201 (2017).

    ADS  Google Scholar 

  26. 26.

    Ambrosio, A., Marrucci, L., Borbone, F., Roviello, A. & Maddalena, P. Light-induced spiral mass transport in azo-polymer films under vortex-beam illumination. Nat. Commun. 3, 1–9 (2012).

    Google Scholar 

  27. 27.

    Peccianti, M. & Assanto, G. Nematicons. Phys. Rep. 516, 147–208 (2012).

    ADS  Google Scholar 

  28. 28.

    Muševič, I. Integrated and topological liquid crystal photonics. Liq. Cryst. 41, 418–429 (2013).

    Google Scholar 

  29. 29.

    Angelsky, O. et al. Orbital rotation without orbital angular momentum: mechanical action of the spin part of the internal energy flow in light beams. Opt. Express 20, 3563–3571 (2012).

    ADS  Google Scholar 

  30. 30.

    Ruffner, D. B. & Grier, D. G. Optical forces and torques in nonuniform beams of light. Phys. Rev. Lett. 108, 173602 (2012).

    ADS  Google Scholar 

  31. 31.

    Antognozzi, M. et al. Direct measurements of the extraordinary optical momentum and transverse spin-dependent force using a nano-cantilever. Nat. Phys. 12, 731–735 (2016).

    Google Scholar 

  32. 32.

    Svak, V. et al. Transverse spin forces and non-equilibrium particle dynamics in a circularly polarized vacuum optical trap. Nat. Commun. 9, 1–8 (2018).

    ADS  Google Scholar 

  33. 33.

    Brasselet, E. Singular optical manipulation of birefringent elastic media using non-singular beams. Opt. Lett. 34, 3229–3231 (2009).

    ADS  Google Scholar 

  34. 34.

    Brasselet, E. Singular optical reordering of liquid crystals using gaussian beams. J. Opt. 12, 124005 (2010).

    ADS  Google Scholar 

  35. 35.

    Bouchard, F. et al. Polarization shaping for control of nonlinear propagation. Phys. Rev. Lett. 117, 233903 (2016).

    ADS  Google Scholar 

  36. 36.

    Gu, B. et al. Varying polarization and spin angular momentum flux of radially polarized beams by anisotropic Kerr media. Opt. Lett. 41, 1566–1569 (2016).

    ADS  Google Scholar 

  37. 37.

    Sakamoto, M. et al. Nonlinear propagation characteristics of a radially polarized beam in a uniaxially aligned dye-doped liquid crystal. J. Opt. Soc. Am. B 36, 3341–3347 (2019).

    ADS  Google Scholar 

  38. 38.

    Lowenthal, S. & Joyeux, D. Speckle removal by a slowly moving diffuser associated with a motionless diffuser. J. Opt. Soc. A 61, 847–851 (1971).

    ADS  Google Scholar 

  39. 39.

    Vedel, M., Breugnot, S. & Lechocinski, N. Full stokes polarization imaging camera. SPIE Proc. 8160, 81600X (2011).

    ADS  Google Scholar 

  40. 40.

    Born, M. & Wolf, E. Principles of Optics (Pergamon, 2005).

  41. 41.

    Durbin, S., Arakelian, S. & Shen, Y. Laser-induced diffraction rings from a nematic-liquid-crystal film. Opt. Lett. 6, 411–413 (1981).

    ADS  Google Scholar 

  42. 42.

    Zolot’ko, A. S. et al. Light-induced second-order phase transition in a spatially bounded region of a nematic liquid crystal. JETP Lett. 36, 80–84 (1982).

    ADS  Google Scholar 

  43. 43.

    Strömer, J., Raynes, E. & Brown, C. Study of elastic constant ratios in nematic liquid crystals. Appl. Phys. Lett. 88, 051915 (2006).

    ADS  Google Scholar 

  44. 44.

    Brasselet, E., Lherbier, A. & Dubé, L. J. Transverse nonlocal effects in optical reorientation of nematic liquid crystals. J. Opt. Soc. Am. B 23, 36–44 (2006).

    ADS  Google Scholar 

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This work has been partially funded by the Research Foundation for Opto-Science and Technology and JSPS KAKENHI (grant no. 20K05364).

Author information




E.B. conceived and supervised the project. All authors contributed to the experimental and theoretical results. E.B. wrote the manuscript with contributions from other authors.

Corresponding author

Correspondence to Etienne Brasselet.

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Extended data

Extended Data Fig. 1 Calculated transverse optical torque density inside the unperturbed anisotropic slab.

Calculated transverse spatial profiles of the normalized optical torque density Cartesian components Γx and Γy for an incident Gaussian field having a linear polarization state oriented along the x axis and propagating along the z axis, where 0≤ξL refers to the propagation distance along the optical axis of the crystal from its input facet that defines ξ = 0. Two values of the internal Gaussian beam divergence angle are considered: θ0 = 1 (a) and θ0 = 10 (b). Each box is centered on (x, y) = (0, 0) and covers an area δL × δL where δ = 2w(z)/L. Each plot is normalized to the maximal value of the plot at ξ = L on the same row and \(\max ({\varGamma }_{x}{| }_{\xi = L})=1.2\times 1{0}^{-3}\max ({\varGamma }_{y}{| }_{\xi = L})\) for θ0 = 1 whereas \(\max ({\varGamma }_{x}{| }_{\xi = L})=0.60\max ({\varGamma }_{y}{| }_{\xi = L})\) for θ0 = 10. Parameters: δ = 1.5, L = 57μm, n = 1.756 and n = 1.528. See Methods for details.

Extended Data Fig. 2 Detailed experimental setup.

Extended version of the illustrative experimental setup shown in Fig. 2(a). BS: non-polarizing beamsplitter for the probe beam. Note that Fig. 2(a) only summarizes the main instrumental ingredients used in practice. Namely, the lens L2 in Fig. 2(a) is an imaging lens for the probe beam in order to observe the director field at the mid-plane of the liquid crystal sample, which corresponds to the 10 × objective lens as shown here. Also, the lens L3 in Fig. 2(a) refers to a collimating lens for the pump beam, which corresponds to a lens system made of a 10 × objective lens followed by a plano-convex lens (f = 100, 150, 200 mm) as shown here. See Methods for details.

Extended Data Fig. 3 Experimental reconstruction of the director field perturbation for incident light with uniform linear polarization state.

Reconstructed spatial distribution of the director field in the mid-plane of the cell \({\tilde{{\bf{n}}}}_{\perp }=({\tilde{n}}_{x},{\tilde{n}}_{y},0)\) as in Fig. 2(b) but for another set of parameters: θ0 = 8. 0, δ = 2.0 and P = 250 mW. Here \(\max | {\tilde{n}}_{y}| /\max | {\tilde{n}}_{x}| \simeq 0.88\). This demonstrates the robustness of the effect versus the diameter of the beam. We notice that the required power to reach the same magnitude for the material response increases with δ whereas choosing δ > 1 facilitates the observations. The latter point can be understood from the fact that the nonlocal character of the nematic response is strengthened as δ decreases 44.

Extended Data Fig. 4 Transverse intensity profiles of the incident vector beams.

Testing the Laguerre-Gaussian lineshapes of the prepared vector beams. Markers: azimuthally-averaged radial intensity profiles measured just before the focusing lens, a × 10 microscope objective with a numerical aperture NA = 0.4. Solid curves: best fit using the Eq. (4).

Extended Data Fig. 5 Pump and probe optical characterization of the customary light-induced Fréedericksz instability.

Experimental determination of the customary optical Fréedericksz instability for θ0 = 1. 6 and δ = 1.7 from the pump beam analysis (a) and from probe beam analysis (b). Set of selected power values that corresponds to the transverse intensity profiles shown in the top row: PA = 231 mW, PB = 235 mW, PC = 246 mW while Pth = 233 ± 1 mW . In panel (a), case C, the luminance has been enhanced on the right side of the image in order to better visualize the self-phase modulation intensity rings.

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El Ketara, M., Kobayashi, H. & Brasselet, E. Sensitive vectorial optomechanical footprint of light in soft condensed matter. Nat. Photonics 15, 121–124 (2021).

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