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Optics Express

Optics Express

  • Editor: Michael Duncan
  • Vol. 12, Iss. 20 — Oct. 4, 2004
  • pp: 4768–4774
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From random to controlled small-scale filamentation in water

H. Schroeder, J. Liu, and S. L. Chin  »View Author Affiliations


Optics Express, Vol. 12, Issue 20, pp. 4768-4774 (2004)
http://dx.doi.org/10.1364/OPEX.12.004768


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Abstract

Simple apertures such as slits and meshes inserted in the beam path of a powerful Ti:Sapphire laser pulse are suitable to produce stable 1-D and 2-D arrays of filaments in liquids. The thus imposed intensity gradients and diffraction patterns can overcome the inherent beam irregularities which naturally give rise to random small-scale multiple filamentations. This method is visualized by means of two photon fluorescence imaging.

© 2004 Optical Society of America

1. Introduction

An important and timely application of the filamentation of powerful femtosecond laser pulses in air is the remote detection of chemical and biological agents using a single laser. Such powerful femtosecond laser pulses can self-transform into white light laser pulses during filamentation in an optical medium [1

1. S. L. Chin, A. Brodeur, S. Petit, O. G. Kosareva, and V. P. Kandidov, “Filamentation and Supercontinuum Generation during the Propagation of Powerful Ultrashort Laser Pulses in Optical Media (White Light Laser),” J. Nonlinear Opt. Phys. Mat. 8, 121–146 (1999). [CrossRef]

,2

2. V.P. Kandidov, O. G. Kosareva, I. S. Golubtsov, W. Liu, A. Becker, N. Akozbek, C. M. Bowden, and S. L. Chin, “Self-transformation of a powerful femtosecond laser pulse into a white-light laser pulse in bulk optical media (or supercontinuum generation),” Appl Phys B 77, 149–165 (2003). [CrossRef]

]. The Teramobile team made use of the back scattered absorption of the white light laser by pollutant molecules in air and demonstrated the potential feasibility of such a remote sensing technique [3

3. J. Kasparian, M. Rodriguez, G. Mejean, J. Yu, E. Salmon, H. Wille, R. Bourayou, S. Frey, Y-B. Andre, A. Mysyrowicz, R. Sauerbrey, J. -P. Wolf, and L. Wöste, “White-light filaments for atmospheric analysis,” Science 301, 61–64 (2003). [CrossRef] [PubMed]

,4

4. P. Rairoux, H. Schillinger, S. Niedermeier, M. Rodriguez, F. Ronneberger, R. Sauerbrey, B. Stein, D. Waite, C. Wedekind, H. Wille, L. Wöste, and C. Ziener, “Remote sensing of the atmosphere using ultrashort laser pulses,” Appl. Phys. B 71, 573–580 (2000). [CrossRef]

]. A complementary technique is the remote sensing of the nonlinear gain fluorescence of molecules inside the filament proposed by one of us (SLC) [5

5. Q. Luo, W. Liu, and S. L. Chin, “Lasing action in air induced by ultra-fast laser filamentation,” Appl. Phys. B 76, 337–340 (2003). [CrossRef]

]. Other long range atmospheric applications could also be envisioned such as target recognition and lightning control [3

3. J. Kasparian, M. Rodriguez, G. Mejean, J. Yu, E. Salmon, H. Wille, R. Bourayou, S. Frey, Y-B. Andre, A. Mysyrowicz, R. Sauerbrey, J. -P. Wolf, and L. Wöste, “White-light filaments for atmospheric analysis,” Science 301, 61–64 (2003). [CrossRef] [PubMed]

], etc.

These potentially important applications rely upon the efficient generation and control of filaments. Note that a small perturbation in the laser pulse front can be amplified efficiently by self-focusing and filamentation [6

6. H. Schroeder and S. L. Chin, “Visualization of the evolution of multiple filaments in methanol,” Opt. Commun. 234, 399–406 (2004). [CrossRef]

]. Since pulse front inhomogeneity occurs in almost all laser pulses and since during propagation, the natural inhomogeneity in the optical medium would lead to further perturbations on the pulse front, multiple filamentation starting from such perturbations would naturally occur. That is to say, multiple filamentation is unavoidable normally when the peak power of the input pulse is high. Moreover, such multiple filaments will undergo competition for energy randomly [6–9

6. H. Schroeder and S. L. Chin, “Visualization of the evolution of multiple filaments in methanol,” Opt. Commun. 234, 399–406 (2004). [CrossRef]

]. Most of the time, the competing filaments die off before becoming mature [6

6. H. Schroeder and S. L. Chin, “Visualization of the evolution of multiple filaments in methanol,” Opt. Commun. 234, 399–406 (2004). [CrossRef]

,7

7. S. A. Hosseini, Q. Luo, B. Ferland, W. Liu, S. L. Chin, O. G. Kosareva, N. A. Panov, N. Akozbek, and V. P. Kandidov, “Competition of multiple filaments during the propagation of intense femtosecond laser pulses,” Phys. Rev. A (to be published).

]. A mature filament is one that has undergone the full processes of self-focusing and filamentation during propagation and will end with self-steepening resulting in the strong spectral broadening (white light laser or supercontinuum) [6

6. H. Schroeder and S. L. Chin, “Visualization of the evolution of multiple filaments in methanol,” Opt. Commun. 234, 399–406 (2004). [CrossRef]

]. This also means that the yield of strong field ionization, fragmentation and subsequent fluorescence of molecules in the path of the filaments in air would be very weak if the filament is not mature [7

7. S. A. Hosseini, Q. Luo, B. Ferland, W. Liu, S. L. Chin, O. G. Kosareva, N. A. Panov, N. Akozbek, and V. P. Kandidov, “Competition of multiple filaments during the propagation of intense femtosecond laser pulses,” Phys. Rev. A (to be published).

].

A practical challenge thus occurs. It calls for a systematic control of multiple filamentation. This means we have to find a way to overcome the natural fluctuations. This is indeed possible by introducing stronger artificial perturbence into the beam path. In Ref. [10

10. S. Minardi, S. Sapone, W. Chinaglia, P. Di Trapani, and A. Berzanskis, “Pixellike parametric generator based on controlled spatial-soliton formation,” Opt. Lett. 25, 326–328 (2000). [CrossRef]

] a lithium triborate parametric generator based on controlled spatial-soliton formation was realized by means of a gridlike photo slide placed in the pump-beam path. Noise-induced multiple filamentation in water could be forced into predictable and highly reproducible filamentation patterns by small input beam ellipticity [11

11. A. Dubietis, G. Tamosauskas, G. Fibich, and B. Ilan, “Multiple filamentation induced by input-beam ellipticity,” Opt. Lett. 29, 1126–1128 (2004). [CrossRef] [PubMed]

]. The possibility to organize regular filamentation patterns in air by imposing either strong field gradients or phase distortions in the input-beam profile has been shown in Ref. [12

12. G. Méchain, A. Couairon, M. Franco, B. Prade, and A. Mysyrowicz, “Organizing Multiple Femtosecond Filaments in Air,” Phys. Rev. Lett. 93, 035003-1, 1–4 (2004). [CrossRef] [PubMed]

]. The principle of the control process is being studied numerically for the propagation of a Ti:Sapphire laser pulse in methanol subjected to random light field fluctuations [13

13. V. P. Kandidov, M. Scalora, O. G. Kosareva, A. V. Nyakk, Q. Luo, S. A. Hosseini, and S. L. Chin, “Towards a control of multiple filamentation by spatial regulation of a high-power femtosecond laser pulse,” Appl. Phys. B submitted, 2004.

].

Here, we demonstrate the persistence of small-scale multiple filamentation when typical Ti: Sapphire laser pulses (2mJ, 50fs, 800nm) propagate in liquids. Then we illustrate the creation of 1-D and 2-D arrays of filaments by launching the beam through appropriate apertures (slits and meshes). In the ideal case multiple filamentation is completely controlled by the superimposed regular diffraction patterns. Furthermore, all filaments evolve nearly identically during the full propagation process as if there were no competition. Similar to Ref. [13

13. V. P. Kandidov, M. Scalora, O. G. Kosareva, A. V. Nyakk, Q. Luo, S. A. Hosseini, and S. L. Chin, “Towards a control of multiple filamentation by spatial regulation of a high-power femtosecond laser pulse,” Appl. Phys. B submitted, 2004.

,14

14. H. Schroeder, invited talk “2-D regular supercontinuum sources from a mesh,” presented at the 2nd International Symposium of Ultrafast Intense Laser Science, Quebec City, Canada, Sept. 25–29, 2003.

], we choose a dye solution as the propagation medium to demonstrate the principle since the critical power for self-focusing is much lower (a few MW) than that of air and since we can directly visualize the filamentation process [6

6. H. Schroeder and S. L. Chin, “Visualization of the evolution of multiple filaments in methanol,” Opt. Commun. 234, 399–406 (2004). [CrossRef]

,14

14. H. Schroeder, invited talk “2-D regular supercontinuum sources from a mesh,” presented at the 2nd International Symposium of Ultrafast Intense Laser Science, Quebec City, Canada, Sept. 25–29, 2003.

].

2. Experimental procedure

Figure 1 illustrates the “natural” situation when a 41fs unfocused Ti:Sapphire laser pulse with a peak power of 6.6×1010 W/cm2 propagates through water (Rhodamine B in water). The bottom self-evident drawing shows the experimental set-up. The overall decrease of the fluorescence intensity along the beam path (top) is mainly caused by the dispersion of the group velocity and the near-infrared absorption of water (α=0.02cm-1). Images of the entrance beam (left pattern) and of the exit beam (right pattern) are also displayed. They represent two photon images from a 1mm thin dye cell. The reddish appearance is caused by the relatively high dye concentration. However, it is still sufficiently low to prevent cross-over effects due to excited dipole-dipole interactions. The indicated diameters refer to the 1/e levels of the two photon images. An obvious advantage of this profile taking technique is due to the fact that the powerful beam does not have to be attenuated (the image signal and the fundamental beam are separated afterwards).

Fig. 1. Two photon fluorescence imaging illustrates small-scale multiple filamentation in water from nearly discernible ripples in the entrance beam (left image). The hot spots in the exit beam (right image) and the enlarged section of the side view demonstrate the appearance of randomly distributed filaments. The individual diameters refer to 1/e levels.

Fig. 2. Creation of a space-fixed 1-D array of filaments by launching the beam through a 200μm wide slit built from razorblades with small mechanical imperfections. The available input intensity was somewhat reduced to avoid white light production along the propagation length. The image shows a side view of developing filaments and the corresponding spot structure of the exit beam.

A simple realization of this concept is depicted in Fig. 3. We introduce a metallic wire mesh into the beam path (11×11 meshes, unit cell 497μm × 497μm, wire width 54μm). The wire mesh creates a symmetric diffraction pattern which changes from position to position along the optical axis. This is exemplified in Fig. 3(a) for six representative distances (13mm to 390mm). The images are false color two photon fluorescence images taken close to the optical axis. The size of each section is 1mm × 1mm, so that we view an entire single mesh and half of the neighboring meshes. Although the generated diffraction patterns appear to be very rich and complicated they can easily be retrieved numerically in terms of Fresnel integrals (this is a practical advantage of rectangular apertures). At a distance of 390mm four bright diffraction spots are located exactly in the shadow region of the wire crosses, in reminiscence of the famous Spot of Arago or Poisson Spot, respectively. The calculated local intensity enhancement with respect to unity entrance intensity is about 4.5, the maximum factor is close to 7. One can choose any pattern and allow it to propagate in the water cell. Those with sufficiently strong intensity modulations would be amplified into white light sources during the nonlinear propagation. Figure 3(b) shows the propagation effect of the corresponding patterns of Fig. 3(a) through the water cell. The output white light patterns show a one to one correspondence to the input patterns. No random hot spots can be detected; i.e., the control of filamentation is complete at least to the extent of the sensitivity of our experiment. In this respect the mesh can be regarded as a simple diffractive optical element (DOE) which serves to concentrate the laser beam into quite peculiar contours [16

16. V. A. Soifer, Methods for Computer Design of Diffractive Optical Elements (John Wiley & Sons, Inc., New York, 2002).

]. Of course, it might also be possible to apply an array of micro lenses for filamentation control [17

17. S. Minardi, A. Varanavicus, A. Piskarskas, and P. Di Trapani, “A compact multi-pixel parametric light source,” Opt. Commun. 224, 301–307 (2003). [CrossRef]

]. However, in this case the fundamental beam is finally divergent. Whereas, in our case, it remains essentially parallel. This aspect considerably simplifies the analysis of the filamentation process.

Fig. 3. Creation of space-controlled 2-D arrays of filaments by launching the beam through a wire mesh (11×11 meshes, mesh 497μm, wire diameter 54μm). (a) Characteristic diffraction patterns for various distances. The shown image sections (1mm×1mm) contain the center mesh and half of its neighbors. (b) Corresponding white light patterns when the dye cell from Fig. 3(a) is replaced by a 10mm water cell.
Fig. 4. Creation of space controlled 1-D arrays of filaments by launching the beam through a slit mesh (11 meshes, the same as in Fig. 3). (a) Side view of filamentation and generation of white light (bright zone on the right) and the corresponding exit image for a mesh to cell distance of 27 mm. (b) Characteristic white light patterns from a 7-mesh slit for various mesh positions. The slit size is given in the right panel for direct comparison.

Figure 4 exemplifies a similar control using a 1-D mesh. Figure 4(a) shows the side-view and the end-view of the periodic and regular filamentation for a mesh to cell distance of 27 mm. Figure 4(b) shows that we can choose the propagation to start from a number of different local symmetries by simply changing the mesh position. The right panel shows the overall mesh size (7 meshes) on the same scale. Again, no random hot spots or uncontrolled filaments can be detected within the sensitivity of our experiment. Because of their simple and variable symmetries, these patterns should also be suitable to investigate white light interferences.

Incidentally, such regular distinctive patterns (1-D and 2-D) after nonlinear propagation could be viewed as a systematic way of writing data storage points inside an appropriate data storage medium. Or, more generally, nonlinear propagation might offer a new technique to enhance small contrasts.

3. Conclusions

In conclusion, we have shown that it is possible to totally overcome multiple filamentation due to natural perturbation of the pulse front of a powerful femtoseocnd laser pulse during nonlinear propagation. The technique we use is to superimpose a regular diffraction structure that could dominate over the random fluctuation. This is possible if the power of the laser inside each element of the regular structure is much higher than the random fluctuations of the field.

References and links

1.

S. L. Chin, A. Brodeur, S. Petit, O. G. Kosareva, and V. P. Kandidov, “Filamentation and Supercontinuum Generation during the Propagation of Powerful Ultrashort Laser Pulses in Optical Media (White Light Laser),” J. Nonlinear Opt. Phys. Mat. 8, 121–146 (1999). [CrossRef]

2.

V.P. Kandidov, O. G. Kosareva, I. S. Golubtsov, W. Liu, A. Becker, N. Akozbek, C. M. Bowden, and S. L. Chin, “Self-transformation of a powerful femtosecond laser pulse into a white-light laser pulse in bulk optical media (or supercontinuum generation),” Appl Phys B 77, 149–165 (2003). [CrossRef]

3.

J. Kasparian, M. Rodriguez, G. Mejean, J. Yu, E. Salmon, H. Wille, R. Bourayou, S. Frey, Y-B. Andre, A. Mysyrowicz, R. Sauerbrey, J. -P. Wolf, and L. Wöste, “White-light filaments for atmospheric analysis,” Science 301, 61–64 (2003). [CrossRef] [PubMed]

4.

P. Rairoux, H. Schillinger, S. Niedermeier, M. Rodriguez, F. Ronneberger, R. Sauerbrey, B. Stein, D. Waite, C. Wedekind, H. Wille, L. Wöste, and C. Ziener, “Remote sensing of the atmosphere using ultrashort laser pulses,” Appl. Phys. B 71, 573–580 (2000). [CrossRef]

5.

Q. Luo, W. Liu, and S. L. Chin, “Lasing action in air induced by ultra-fast laser filamentation,” Appl. Phys. B 76, 337–340 (2003). [CrossRef]

6.

H. Schroeder and S. L. Chin, “Visualization of the evolution of multiple filaments in methanol,” Opt. Commun. 234, 399–406 (2004). [CrossRef]

7.

S. A. Hosseini, Q. Luo, B. Ferland, W. Liu, S. L. Chin, O. G. Kosareva, N. A. Panov, N. Akozbek, and V. P. Kandidov, “Competition of multiple filaments during the propagation of intense femtosecond laser pulses,” Phys. Rev. A (to be published).

8.

W. Liu, S. A Hosseini, Q. Luo, B. Ferland, S. L. Chin, O. G. Kosareva, N. A. Panov, and V. P. Kandidov, “Experimental observation and simulations of the self-action of white light laser pulse propagating in air,” New Journal of Physics V. 6, P. 6 (2004). [CrossRef]

9.

G. Mechain, A. Couairon, Y. -B. Andre, C. D. Amico, M. Franco, B. Prade, S. Tzortzakis, A. Mysyrowicz, and R. Sauerbery, “Long-range self-channeling of infrared laser pulses in air: a new propation regime without ionization,” Appl. Phys. B 79, 379–382 (2004). [CrossRef]

10.

S. Minardi, S. Sapone, W. Chinaglia, P. Di Trapani, and A. Berzanskis, “Pixellike parametric generator based on controlled spatial-soliton formation,” Opt. Lett. 25, 326–328 (2000). [CrossRef]

11.

A. Dubietis, G. Tamosauskas, G. Fibich, and B. Ilan, “Multiple filamentation induced by input-beam ellipticity,” Opt. Lett. 29, 1126–1128 (2004). [CrossRef] [PubMed]

12.

G. Méchain, A. Couairon, M. Franco, B. Prade, and A. Mysyrowicz, “Organizing Multiple Femtosecond Filaments in Air,” Phys. Rev. Lett. 93, 035003-1, 1–4 (2004). [CrossRef] [PubMed]

13.

V. P. Kandidov, M. Scalora, O. G. Kosareva, A. V. Nyakk, Q. Luo, S. A. Hosseini, and S. L. Chin, “Towards a control of multiple filamentation by spatial regulation of a high-power femtosecond laser pulse,” Appl. Phys. B submitted, 2004.

14.

H. Schroeder, invited talk “2-D regular supercontinuum sources from a mesh,” presented at the 2nd International Symposium of Ultrafast Intense Laser Science, Quebec City, Canada, Sept. 25–29, 2003.

15.

W. Koechner, Solid-State Laser Engineering (Springer-Verlag Heidelberg New York, 1988).

16.

V. A. Soifer, Methods for Computer Design of Diffractive Optical Elements (John Wiley & Sons, Inc., New York, 2002).

17.

S. Minardi, A. Varanavicus, A. Piskarskas, and P. Di Trapani, “A compact multi-pixel parametric light source,” Opt. Commun. 224, 301–307 (2003). [CrossRef]

OCIS Codes
(190.5530) Nonlinear optics : Pulse propagation and temporal solitons
(190.7110) Nonlinear optics : Ultrafast nonlinear optics
(320.7130) Ultrafast optics : Ultrafast processes in condensed matter, including semiconductors

ToC Category:
Research Papers

History
Original Manuscript: August 20, 2004
Revised Manuscript: September 16, 2004
Published: October 4, 2004

Citation
H. Schroeder, J. Liu, and S. Chin, "From random to controlled small-scale filamentation in water," Opt. Express 12, 4768-4774 (2004)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-12-20-4768


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References

  1. S. L. Chin, A. Brodeur, S. Petit, O. G. Kosareva, and V. P. Kandidov, �??Filamentation and Supercontinuum Generation during the Propagation of Powerful Ultrashort Laser Pulses in Optical Media (White Light Laser),�?? J. Nonlinear Opt. Phys. Mat. 8, 121-146 (1999). [CrossRef]
  2. V.P. Kandidov, O. G. Kosareva, I. S. Golubtsov, W. Liu, A. Becker, N. Akozbek, C. M. Bowden, and S. L. Chin, �??Self-transformation of a powerful femtosecond laser pulse into a white-light laser pulse in bulk optical media (or supercontinuum generation),�?? Appl Phys B 77, 149-165 (2003). [CrossRef]
  3. J. Kasparian, M. Rodriguez, G. Mejean, J. Yu, E. Salmon, H. Wille, R. Bourayou, S. Frey, Y-B. Andre, A. Mysyrowicz, R. Sauerbrey, J. �??P. Wolf, and L. Wöste, �??White-light filaments for atmospheric analysis,�?? Science 301, 61-64 (2003). [CrossRef] [PubMed]
  4. P. Rairoux, H. Schillinger, S. Niedermeier, M. Rodriguez, F. Ronneberger, R. Sauerbrey, B. Stein, D. Waite, C.Wedekind, H. Wille, L.Wöste, and C. Ziener, �??Remote sensing of the atmosphere using ultrashort laser pulses,�?? Appl. Phys. B 71, 573-580 (2000). [CrossRef]
  5. Q. Luo, W. Liu, and S. L. Chin, �??Lasing action in air induced by ultra-fast laser filamentation,�?? Appl. Phys. B 76, 337-340 (2003). [CrossRef]
  6. H. Schroeder and S. L. Chin, �??Visualization of the evolution of multiple filaments in methanol,�?? Opt. Commun. 234, 399-406 (2004). [CrossRef]
  7. S. A. Hosseini, Q. Luo, B. Ferland, W. Liu, S. L. Chin, O. G. Kosareva, N. A. Panov, N. Akozbek, and V. P. Kandidov, Competition of multiple filaments during the propagation of intense femtosecond laser pulses,�?? Phys. Rev. A (to be published).
  8. W. Liu, S. A Hosseini, Q. Luo, B. Ferland, S. L. Chin, O. G. Kosareva, N. A. Panov, and V. P. Kandidov, �??Experimental observation and simulations of the self-action of white light laser pulse propagating in air,�?? New Journal of Physics V. 6, P. 6 (2004). [CrossRef]
  9. G. Mechain, A. Couairon, Y. �??B. Andre, C. D. Amico, M. Franco, B. Prade, S. Tzortzakis, A. Mysyrowicz, and R. Sauerbery, �??Long-range self-channeling of infrared laser pulses in air: a new propation regime without ionization,�?? Appl. Phys. B 79, 379-382 (2004). [CrossRef]
  10. S. Minardi, S. Sapone, W. Chinaglia, P. Di Trapani, and A. Berzanskis, �??Pixellike parametric generator based on controlled spatial-soliton formation,�?? Opt. Lett. 25, 326-328 (2000). [CrossRef]
  11. A. Dubietis, G. Tamosauskas, G. Fibich, and B. Ilan, �??Multiple filamentation induced by input-beam ellipticity,�?? Opt. Lett. 29, 1126-1128 (2004). [CrossRef] [PubMed]
  12. G. Méchain, A. Couairon, M. Franco, B. Prade, and A. Mysyrowicz, �??Organizing Multiple Femtosecond Filaments in Air,�?? Phys. Rev. Lett. 93, 035003-1, 1-4 (2004). [CrossRef] [PubMed]
  13. V. P. Kandidov, M. Scalora, O. G. Kosareva, A. V. Nyakk, Q. Luo, S. A. Hosseini, S. L. Chin, �??Towards a control of multiple filamentation by spatial regulation of a high-power femtosecond laser pulse,�?? Appl. Phys. B submitted, 2004.
  14. H. Schroeder, invited talk �??2-D regular supercontinuum sources from a mesh,�?? presented at the 2nd International Symposium of Ultrafast Intense Laser Science, Quebec City, Canada, Sept. 25-29, 2003.
  15. W. Koechner, Solid-State Laser Engineering (Springer-Verlag Heidelberg New York, 1988).
  16. V. A. Soifer, Methods for Computer Design of Diffractive Optical Elements (John Wiley & Sons, Inc., New York, 2002).
  17. S. Minardi, A. Varanavicus, A. Piskarskas, and P. Di Trapani, �??A compact multi-pixel parametric light source,�?? Opt. Commun. 224, 301-307 (2003). [CrossRef]

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