OSA's Digital Library

Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 20, Iss. 24 — Nov. 19, 2012
  • pp: 27369–27375
« Show journal navigation

Shock wave far-field in ordered and disordered nonlocal media

S. Gentilini, N. Ghofraniha, E. DelRe, and C. Conti  »View Author Affiliations


Optics Express, Vol. 20, Issue 24, pp. 27369-27375 (2012)
http://dx.doi.org/10.1364/OE.20.027369


View Full Text Article

Acrobat PDF (2470 KB)





Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations

Abstract

We investigate the far field of a spatial dispersive shock wave generated from a Gaussian beam propagating in nonlinear nonlocal colloidal disordered media. The interplay between nonlinearity and structural randomness is quantified in terms of the threshold power for the occurrence of the shock wave.

© 2012 OSA

1. Introduction

Recent experimental investigations have shown that the wavevector content of an optical beam in the presence of pronounced nonlinear effects may signal the occurrence of specific dynamic phases and self organization for light [1

1. C. Sun, J. Schu, C. Barsi, S. Rica, A. Picozzi, and J. W. Fleischer, “Observation of the kinetic condensation of classical waves,” Nat. Phys. 8, 471–475 (2012). [CrossRef]

, 2

2. W. Wan, S. Jia, and J. W. Fleischer, “Dispersive superfluid-like shock waves in nonlinear optics,” Nat. Phys. 3, 46–51 (2007). [CrossRef]

]. The way these phenomena are affected by disorder is not yet investigated. Following recent theoretical investigations concerning the complexity of nonlinear waves in the presence of structural randomness [3

3. C. Conti and L. Leuzzi, “Complexity of waves in nonlinear disordered media,” Phys. Rev. B 83, 134204 (2011). [CrossRef]

9

9. I. V. Shadrivov, K. Y. Bliokh, V. Freilikher, and Y. S. Kivshar, “Bistability of Anderson localized states in nonlinear random media,” Phys. Rev. Lett. 104, 123902 (2010). [CrossRef] [PubMed]

], experimental efforts are focused on finding a coherent and nonlinearly driven effect that can be largely affected even by a small amount of disorder, which must be in some way controllable [10

10. Y. Lahini, A. Avidan, F. Pozzi, M. Sorel, R. Morandotti, D. N. Christodoulides, and Y. Silberberg, “Anderson localization and nonlinearity in onedimensional disorded photonic lattices,” Phys. Rev. Lett. 100, 013906 (2008). [CrossRef] [PubMed]

13

13. L. Levi, M. Rechtsman, B. Freedman, T. Schwartz, and M. Segev, “Disorder-enhanced transport in photonics quasicrystals,” Science 332, 1541–1544 (2011). [CrossRef] [PubMed]

].

Here we consider the generation and evolution of dispersive shock waves (DSWs) in a thermal nonlocal nonlinear liquid medium [14

14. N. Ghofraniha, C. Conti, G. Ruocco, and S. Trillo, “Shocks in nonlocal media,” Phys. Rev. Lett. 99, 043903 (2007). [CrossRef] [PubMed]

16

16. N. Ghofraniha, L. Santamaria Amato, V. Folli, C. Conti, and E. DelRe, “Formation and propagation of shock waves in nonlocal media,” Poster number JM5A.44 presented at Nonlinear Photonics Conference, Colorado Springs, CO, USA, 17–21 June 2012.

] into which we introduce controllable disorder using a colloidal dispersion of low index contrast dielectric particles. DSWs, or undular bores, are observed in nonlinear optics in systems described by universal models, such as the nonlinear Schrödinger (NLS) equation when the hydrodynamical approximation holds true [17

17. A. Gurevich and L. P. Pitaevskii, “Stationary structure of a collisionless shock wave,” Sov.Phys. JETP 38, 291–297 (1973).

21

21. C. Barsi, W. Wan, C. Sun, and J. W. Fleischer, “Dispersive shock waves with nonlocal nonlinearity,” Opt. Lett. 32, 2930–2932 (2007). [CrossRef] [PubMed]

]. In the spatial case here considered, this corresponds to the regime when the nonlinear length is much smaller than the diffraction and loss (absorption and scattering) lengths.

2. Sample preparation and experimental set-up

As previously reported [14

14. N. Ghofraniha, C. Conti, G. Ruocco, and S. Trillo, “Shocks in nonlocal media,” Phys. Rev. Lett. 99, 043903 (2007). [CrossRef] [PubMed]

16

16. N. Ghofraniha, L. Santamaria Amato, V. Folli, C. Conti, and E. DelRe, “Formation and propagation of shock waves in nonlocal media,” Poster number JM5A.44 presented at Nonlinear Photonics Conference, Colorado Springs, CO, USA, 17–21 June 2012.

], an ordered nonlocal medium is realized by aqueous suspensions of RhodamineB (RhB). We consider different RhB concentrations, cRhB, ranging from 0.05 to 0.5 mM (samples series A). The disordered samples (samples series B) are obtained by adding mono-dispersed 1μm diameter silica (SiO2) spheres with concentrations, cSiO2, ranging from 0.005 w/w to 0.035 w/w, in units of weight of silica particles over suspension weight. By varying cRhB and cSiO2 we tailor the amount of nonlinearity, as detailed below, and the strength of disorder.

The samples are put in 1mm×1cm×3cm glass cells with propagation direction z along the 1 mm vertical direction, which is set parallel to the gravity vector to moderate the effect of heat convection.

A continuous-wave solid state laser at wavelength λ = 532 nm is focused on the input facet of the cell at the beam radius waist w0 = 50μm. A lens of focal length f = 75mm, placed at the same distance f from the output face of the cell and from the detector, allows the measurements of the spatial Fourier transform of the transmitted beam by imaging on a 1024 × 1032 pixel CCD camera. Having fixed the geometrical configuration of the experiment, we proceeded to calibrate the CCD by fitting with the Airy function the experimentally obtained Fourier transform of a 500μm diameter pinhole, placed on the exit face of the cell. In this way we were able to obtain the conversion from pixel to radians. The angular spreading θ was then translated in terms of transverse (with respect to z) wavevectors kT as kT = (2π/λ)sin(θ).

Fig. 1 Beam propagation as observed from top fluorescence emission for three different input powers in the ordered case, cSiO2 = 0 (cRhB = 0.1mM), (a–c) and disordered case, cSiO2 = 0.03w/w (cRhB = 0.1mM), (d–f). Note that the propagation regime reported in panel (a) is linear since the laser power is too low to activate the nonlinear effect.

Upper panels (a–c) show the propagation of the beam in the ordered sample, i.e. at cSiO2 = 0 (cRhB = 0.1mM), while the bottom panels (d–f) the propagation within a disordered sample at cSiO2 = 0.03w/w (cRhB = 0.1mM). The shock formation is characterized by the fact that the laser beam displays regularizing oscillation. The panels (a–c) show the shock formation as the oscillations are clearly visible with the increase of power, nevertheless another phenomenon can be noticed to accompanying the oscillations: the diffraction enhancement resulting in a funnel shape with the increase of input power. The far field manifests the generation of characteristic rings (Fig. 2), whose size depends on dye concentration, strength of disorder and laser power.

Fig. 2 Far field intesity of the transmitted beam for different input powers P and different concentrations cRhB (ordered case). Superimposed curves give the ky = 0 section profile. Similarly to Fig. 1(a), here the top panels (a–c) show a linear regime since the laser power is too low to activate the nonlinear effect.

3. Shock wave far field in the ordered case

We first consider the ordered case: we investigate the occurrence of DSW when varying input laser power P for different concentrations of RhB, cRhB, in the pure dye solutions (samples series A, cSiO2 = 0).

In Fig. 2 we show images of the intensity of the far field of the transmitted beam. The spectra display a progressive enlargement in the wavevector plane with P. In order to quantify such an effect we make a radial average of the 2-D collected profiles and we measure the angular aperture θ as the full width at half maximum of the peak, as long as a single peak is observed; and as the distance between the two leading peaks, when these become distinguishable after the formation of the shock wave.

We stress that when increasing cRhB, the amount of nonlinearity increases because of the enhanced absorption. Figure 3(a) shows the angular aperture θ versus P for different RhB concentrations. Two effects are evident: 1) by increasing P, θ increases because of the speedup of the shock formation by the augmented nonlinearity. Moreover the slope of the curves increases due to the fact that nonlinearity grows with cRhB, hence higher angular aperture is obtained at the same power P. 2) There exists a threshold power, Pth, above which θ becomes linear with P, and this threshold decreases when increasing cRhB (Fig. 3(a)).

Fig. 3 (a) Measured aperture angle vs laser power P in the ordered case for different cRhB concentrations; (b) P vs cRhB: the filled circles are the experimental threshold power as retrieved from panel (a) (dot-dashed lines is a guide for the eye).

4. Shock wave far field in the disordered case

We consider the interplay between disorder and nonlinearity in the DSW formation by dispersing the 1μm diameter SiO2 spheres in two different aqueous solutions of RhB at cRhB = 0.05 mM and cRhB = 0.1 mM (samples series B).

Figure 4 shows the spectral profiles for different cSiO2 and cRhB at fixed power P = 40 mW. At this input laser power, no shock formation emerges from the spectra at the lowest cRhB (panels (a–c)). On the other hand, the spectra reported in Fig. 4(d–f) show the characteristic rings signature of DSW formation. Note that the circular symmetry is lost because of the inhomogeneous refractive index and that DSW is more evident in some directions than in others. In other words, the shock wave has a partially randomized spatial distribution. The DSW is more evident at the second higher considered RhB concentration, where the nonlinearity is enhanced.

Fig. 4 Spectra of transmitted beam at fixed input power P=42 mW and different cRhB and cSiO2.

In Fig. 5 we show the case P = 140 mW. Even at the lowest cRhB there are evidences of rings, top panels in Fig. 5. DSW formation is more pronounced in the case of cRhB = 0.1 mM (Fig. 5(d–f)).

Fig. 5 The same of Fig. 4 at input power P=130 mW

The angular aperture θ vs power is shown in Fig. 6(a) and 6(b) for different cSiO2, when cRhB = 0.05 mM and 0.1 mM respectively. The curves provide information on the competition between nonlinearity and disorder. For the lowest concentration of dye (cRhB = 0.05mM), as shown in Fig. 6(a), disorder prevails over nonlinearity, preventing the occurrence of DSW and no threshold is observed (compare with the ordered case, circles in Fig. 6(a)). In Fig. 6(b) we show the results at higher dye concentration cRhB = 0.1 mM; we observe the threshold behavior as in the ordered case. However, the hampering effect of randomness is revealed by the fact that the aperture angle at a given power is smaller than the case cSiO2 = 0; in addition, when cSiO2 is greater than 0.017 w/w no shock formation is observed as shown for cSiO2 = 0.035 w/w in Fig. 6(b). Similarly to the ordered case, we extract from Fig. 6(b), a diagram of the threshold power Pth versus cSiO2 (Fig. 6(c)).

Fig. 6 Measured aperture angle θ vs laser power P for different SiO2 dispersions in two RhB solutions: (a) cRhB = 0.05mM and (b) cRhB = 0.1mM; (c) threshold power P vs disorder concentrations cSiO2 at fixed cRhB = 0.1mM: dots are the experimental data, dot dashed lines is a guide for the eye, dashed line is the boundary between shock and no shock regimes.

In order to furnish quantitative arguments to support the reported results, we estimate the ratio between the nonlinear and the random contribution to the refractive index. We expect that disorder completely washes out the shock phenomenon when the volume average of the index perturbation due to the silica spheres is comparable with the index perturbation due to nonlinearity. The nonlinear perturbation can be estimated of the order 10−3. By considering the refractive index of the silica particles (nSiO2 ≃ 1.4) and their concentration, this index perturbation is found at the concentration cSiO2 ≃ 0.03w/w, consistently with data of Fig. 6(c).

5. Conclusion

The analysis of the far field of dispersive shock waves generated in a nonlocal nonlinear medium allows the investigation of the interplay between disorder-induced and spontaneous wave breaking phenomena. In the ordered case, we have shown that the angular aperture of the beam versus power provides a simple way to determine the threshold for the generation of the shock; this threshold power decreases with the amount of nonlinearity, controlled by dye concentrations in our samples.

In the presence of disorder, loss of transverse spatial coherence prevents the occurrence of the spontaneous wave breaking. The shock is observed above a certain amount of nonlinearity and below a critical strength of disorder. We show these phenomena can also be quantified by measuring the threshold power in terms of the strength of randomness, controlled by the concentrations of colloidal suspension which is used to introduce scattering.

Investigating the spatial spectral distribution of waves in the presence of strong nonlinearity and disorder may lead to future developments in assessing dynamic phase transitions and structured landscapes for light.

Acknowledgments

The research leading to these results has received funding from the European Research Council under the European Community’s Seventh Framework Program (FP7/2007–2013)/ERC grant agreement n. 201766, from the Italian Ministry of Research (MIUR) through the PRIN project no.2009P3K72Z and from the Italian Ministry of Education, University and Research under the Basic Research Investigation Fund (FIRB/2008) program/CINECA grant code RBFR08M3P4 and RBFR08E7VA. We thank M. Deen Islam for the technical assistance.

References and links

1.

C. Sun, J. Schu, C. Barsi, S. Rica, A. Picozzi, and J. W. Fleischer, “Observation of the kinetic condensation of classical waves,” Nat. Phys. 8, 471–475 (2012). [CrossRef]

2.

W. Wan, S. Jia, and J. W. Fleischer, “Dispersive superfluid-like shock waves in nonlinear optics,” Nat. Phys. 3, 46–51 (2007). [CrossRef]

3.

C. Conti and L. Leuzzi, “Complexity of waves in nonlinear disordered media,” Phys. Rev. B 83, 134204 (2011). [CrossRef]

4.

S. A. Gredeskul and Y. S. Kivshar, “Propagation and scattering of nonlinear waves in disordered systems,” Phys. Rep. 216, 1–61 (1992). [CrossRef]

5.

Y. V. Kartashov, V. A. Vysloukh, and L. Torner, “Soliton percolation in random optical lattices,” Opt. Express 15, 12409–12417 (2007). [CrossRef] [PubMed]

6.

Y. S. Kivshar, S. A. Gredeskul, A. Sanchez, and L. Vazquez, “Localization decay induced by strong nonlinearity in disordered systems,” Phys. Rev. Lett. 64, 1693–1696 (1990). [CrossRef] [PubMed]

7.

A. Pikovsky and S. Fishman, “Scaling properties of weak chao in nonlinear disordered lattcies,” Phys. Rev. E 83, 025201 (2011). [CrossRef]

8.

Z. V. Vardeny and A. Nahata, “Photonic quasicrystals: disorder-enhanced light transport,” Nat. Photonics 5, 453–454 (2011). [CrossRef]

9.

I. V. Shadrivov, K. Y. Bliokh, V. Freilikher, and Y. S. Kivshar, “Bistability of Anderson localized states in nonlinear random media,” Phys. Rev. Lett. 104, 123902 (2010). [CrossRef] [PubMed]

10.

Y. Lahini, A. Avidan, F. Pozzi, M. Sorel, R. Morandotti, D. N. Christodoulides, and Y. Silberberg, “Anderson localization and nonlinearity in onedimensional disorded photonic lattices,” Phys. Rev. Lett. 100, 013906 (2008). [CrossRef] [PubMed]

11.

L. Martin, G. Di Giuseppe, A. Perez-Leija, R. Keil, F. Dreisow, M. Heinrich, S. Nolte, A. Szameit, A. F. Abouraddy, D. N. Christodoulides, and B. E. A. Saleh, “Anderson localization in optical waveguide arrays with off-diagonal coupling disorder,” Opt. Express 19, 13636–13646 (2011). [CrossRef] [PubMed]

12.

T. Schwartz, G. Bartal, S. Fishman, and M. Segev, “Transport and Anderson localization in disordered two-dimensional photonic lattices,” Nature 446, 52–55 (2007). [CrossRef] [PubMed]

13.

L. Levi, M. Rechtsman, B. Freedman, T. Schwartz, and M. Segev, “Disorder-enhanced transport in photonics quasicrystals,” Science 332, 1541–1544 (2011). [CrossRef] [PubMed]

14.

N. Ghofraniha, C. Conti, G. Ruocco, and S. Trillo, “Shocks in nonlocal media,” Phys. Rev. Lett. 99, 043903 (2007). [CrossRef] [PubMed]

15.

N. Ghofraniha, L. Santamaria Amato, V. Folli, S. Trillo, E. DelRe, and C. Conti, “Measurement of scaling laws for shock waves in thermal nonlocal media,” Opt. Lett. 37, 2325–2327 (2012). [CrossRef] [PubMed]

16.

N. Ghofraniha, L. Santamaria Amato, V. Folli, C. Conti, and E. DelRe, “Formation and propagation of shock waves in nonlocal media,” Poster number JM5A.44 presented at Nonlinear Photonics Conference, Colorado Springs, CO, USA, 17–21 June 2012.

17.

A. Gurevich and L. P. Pitaevskii, “Stationary structure of a collisionless shock wave,” Sov.Phys. JETP 38, 291–297 (1973).

18.

J. C. Bronski and D. McLaughlin, Singular Limits of Dispersive Waves (Plenum, New York, 1994).

19.

A. M. Kamchatnov, R. A. Kraenkel, and B. A. Umarov, “Asymptotic soliton train solution of the defocusing nonlinear Schrödinger equation,” Phys. Rev. E 66, 036609 (2002). [CrossRef]

20.

C. Conti, A. Fratalocchi, M. Peccianti, G. Ruocco, and S. Trillo, “Observation of a gradient catastrophe generating solitons,” Phys. Rev. Lett. 102, 083902 (2009). [CrossRef] [PubMed]

21.

C. Barsi, W. Wan, C. Sun, and J. W. Fleischer, “Dispersive shock waves with nonlocal nonlinearity,” Opt. Lett. 32, 2930–2932 (2007). [CrossRef] [PubMed]

OCIS Codes
(190.0190) Nonlinear optics : Nonlinear optics
(190.3970) Nonlinear optics : Microparticle nonlinear optics
(190.4720) Nonlinear optics : Optical nonlinearities of condensed matter

ToC Category:
Materials

History
Original Manuscript: September 4, 2012
Revised Manuscript: October 16, 2012
Manuscript Accepted: October 17, 2012
Published: November 19, 2012

Virtual Issues
Nonlinear Photonics (2012) Optics Express

Citation
S. Gentilini, N. Ghofraniha, E. DelRe, and C. Conti, "Shock wave far-field in ordered and disordered nonlocal media," Opt. Express 20, 27369-27375 (2012)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-20-24-27369


Sort:  Author  |  Year  |  Journal  |  Reset  

References

  1. C. Sun, J. Schu, C. Barsi, S. Rica, A. Picozzi, and J. W. Fleischer, “Observation of the kinetic condensation of classical waves,” Nat. Phys.8, 471–475 (2012). [CrossRef]
  2. W. Wan, S. Jia, and J. W. Fleischer, “Dispersive superfluid-like shock waves in nonlinear optics,” Nat. Phys.3, 46–51 (2007). [CrossRef]
  3. C. Conti and L. Leuzzi, “Complexity of waves in nonlinear disordered media,” Phys. Rev. B83, 134204 (2011). [CrossRef]
  4. S. A. Gredeskul and Y. S. Kivshar, “Propagation and scattering of nonlinear waves in disordered systems,” Phys. Rep.216, 1–61 (1992). [CrossRef]
  5. Y. V. Kartashov, V. A. Vysloukh, and L. Torner, “Soliton percolation in random optical lattices,” Opt. Express15, 12409–12417 (2007). [CrossRef] [PubMed]
  6. Y. S. Kivshar, S. A. Gredeskul, A. Sanchez, and L. Vazquez, “Localization decay induced by strong nonlinearity in disordered systems,” Phys. Rev. Lett.64, 1693–1696 (1990). [CrossRef] [PubMed]
  7. A. Pikovsky and S. Fishman, “Scaling properties of weak chao in nonlinear disordered lattcies,” Phys. Rev. E83, 025201 (2011). [CrossRef]
  8. Z. V. Vardeny and A. Nahata, “Photonic quasicrystals: disorder-enhanced light transport,” Nat. Photonics5, 453–454 (2011). [CrossRef]
  9. I. V. Shadrivov, K. Y. Bliokh, V. Freilikher, and Y. S. Kivshar, “Bistability of Anderson localized states in nonlinear random media,” Phys. Rev. Lett.104, 123902 (2010). [CrossRef] [PubMed]
  10. Y. Lahini, A. Avidan, F. Pozzi, M. Sorel, R. Morandotti, D. N. Christodoulides, and Y. Silberberg, “Anderson localization and nonlinearity in onedimensional disorded photonic lattices,” Phys. Rev. Lett.100, 013906 (2008). [CrossRef] [PubMed]
  11. L. Martin, G. Di Giuseppe, A. Perez-Leija, R. Keil, F. Dreisow, M. Heinrich, S. Nolte, A. Szameit, A. F. Abouraddy, D. N. Christodoulides, and B. E. A. Saleh, “Anderson localization in optical waveguide arrays with off-diagonal coupling disorder,” Opt. Express19, 13636–13646 (2011). [CrossRef] [PubMed]
  12. T. Schwartz, G. Bartal, S. Fishman, and M. Segev, “Transport and Anderson localization in disordered two-dimensional photonic lattices,” Nature446, 52–55 (2007). [CrossRef] [PubMed]
  13. L. Levi, M. Rechtsman, B. Freedman, T. Schwartz, and M. Segev, “Disorder-enhanced transport in photonics quasicrystals,” Science332, 1541–1544 (2011). [CrossRef] [PubMed]
  14. N. Ghofraniha, C. Conti, G. Ruocco, and S. Trillo, “Shocks in nonlocal media,” Phys. Rev. Lett.99, 043903 (2007). [CrossRef] [PubMed]
  15. N. Ghofraniha, L. Santamaria Amato, V. Folli, S. Trillo, E. DelRe, and C. Conti, “Measurement of scaling laws for shock waves in thermal nonlocal media,” Opt. Lett.37, 2325–2327 (2012). [CrossRef] [PubMed]
  16. N. Ghofraniha, L. Santamaria Amato, V. Folli, C. Conti, and E. DelRe, “Formation and propagation of shock waves in nonlocal media,” Poster number JM5A.44 presented at Nonlinear Photonics Conference, Colorado Springs, CO, USA, 17–21 June 2012.
  17. A. Gurevich and L. P. Pitaevskii, “Stationary structure of a collisionless shock wave,” Sov.Phys. JETP38, 291–297 (1973).
  18. J. C. Bronski and D. McLaughlin, Singular Limits of Dispersive Waves (Plenum, New York, 1994).
  19. A. M. Kamchatnov, R. A. Kraenkel, and B. A. Umarov, “Asymptotic soliton train solution of the defocusing nonlinear Schrödinger equation,” Phys. Rev. E66, 036609 (2002). [CrossRef]
  20. C. Conti, A. Fratalocchi, M. Peccianti, G. Ruocco, and S. Trillo, “Observation of a gradient catastrophe generating solitons,” Phys. Rev. Lett.102, 083902 (2009). [CrossRef] [PubMed]
  21. C. Barsi, W. Wan, C. Sun, and J. W. Fleischer, “Dispersive shock waves with nonlocal nonlinearity,” Opt. Lett.32, 2930–2932 (2007). [CrossRef] [PubMed]

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.


« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited