OSA's Digital Library

Optics Express

Optics Express

  • Editor: Michael Duncan
  • Vol. 10, Iss. 14 — Jul. 15, 2002
  • pp: 603–608
« Show journal navigation

Motion of bubble in solid by femtosecond laser pulses

Wataru Watanabe and Kazuyoshi Itoh  »View Author Affiliations


Optics Express, Vol. 10, Issue 14, pp. 603-608 (2002)
http://dx.doi.org/10.1364/OE.10.000603


View Full Text Article

Acrobat PDF (117 KB)





Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations

Abstract

We report that irradiation of femtosecond laser pulses moves a microscopic bubble inside crystalline calcium fluoride and amorphous silica glass. In situ observation revealed that the bubble moves against the direction of propagation of laser pulses as far as 2 microns. We also demonstrate the lateral movement of a void along the axis perpendicular to the beam propagation axis by shifting the laser focus.

© 2002 Optical Society of America

1. Introduction

When a femtosecond laser pulse is focused inside a bulk of transparent material, the intensity in a focal volume becomes high enough to produce microscopic structural modifications through nonlinear optical absorption. The modifications have been utilized as optical data-storage elements [1–3

1. E. N. Glezer, M. Milosavljevic, L. Huang, R. J. Finlay, T.-H. Her, J. P. Callan, and E. Mazur, “Three-dimensional optical storage inside transparent materials,” Opt. Lett. 21, 2023–2025 (1996). [CrossRef] [PubMed]

], waveguides [4–8

4. K. M. Davis, K. Miura, N. Sugimoto, and H. Hirao, “Writing waveguides in glass with a femtosecond laser,” Opt. Lett. 21, 1729–1731 (1996). [CrossRef] [PubMed]

], gratings [9

9. L. Sudrie, M. Franco, B. Prade, and A. Mysyrowicz, ”Writing of permanent birefringent microlayers in bulk fused silica with femtosecond laser pulses,“ Opt. Commun. 171, 279–284 (1999). [CrossRef]

], and couplers [8

8. D. Homoelle, W. Wielandy, A. L. Gaeta, E. F. Borrelli, and C. Smith, “Infraredphotosensitivity in silica glasses exposed to femtosecondlaser pulses,” Opt. Lett. 24, 1311–1313 (1999). [CrossRef]

,10

10. A. M. Streltsov and N. F. Borrelli, “Fabrication and analysis of a directional coupler written in glass by nanojoule femtosecond laser pulses,” Opt. Lett. 26, 42–44 (2001). [CrossRef]

,11

11. C. B. Schaffer, A. Brodeur, and E. Mazur, “Laser-induced breakdown and damage in bulk transparent materials induced by tightly focused femtosecond laser pulses,” Meas. Sci. Technol. 12, 1784–1794 (2001). [CrossRef]

] inside a wide variety of transparent materials including glasses, crystals, and plastics. The submicrometer-damages that are produced by femtosecond laser pulses with high numerical-aperture (NA) lenses were demonstrated to be cavities or voids surrounded by densified materials [1

1. E. N. Glezer, M. Milosavljevic, L. Huang, R. J. Finlay, T.-H. Her, J. P. Callan, and E. Mazur, “Three-dimensional optical storage inside transparent materials,” Opt. Lett. 21, 2023–2025 (1996). [CrossRef] [PubMed]

,2

2. N. Glezer and E. Mazur, “Ultrafast-laser driven micro-explosions in transparent materials,” Appl. Phys. Lett. 71, 882–884 (1997). [CrossRef]

]. Glezer et al. described the mechanism of the formation of the void as follows: When the laser pulse is tightly focused, hot electrons and ions explosively expand from the focal volume into the surrounding material due to the very high energy density produced by the femtosecond optical breakdown. We have shown that after producing a void or bubble in bulk glass by irradiation with intense femtosecond laser pulses it could be moved by shifting the laser focus slightly in front of the void and irradiating again [3

3. W. Watanabe, T. Toma, K. Yamada, J. Nishii, K. Hayashi, and K. Itoh, “Optical seizing and merging of voids in silica glass with infrared femtosecond laser pulses,” Opt. Lett. 25, 1669–1671 (2000). [CrossRef]

]. We found we could move the void only in the direction opposite to the laser propagation direction up to 5 μm. We explained the mechanism as follows: Femtosecond laser irradiation produces a void in the glass. When a subsequent laser pulse if focused slightly in front of the void, it vaporized the material there. This hot material fills in the old void, leaving a new void slightly upstream from the original.

In this paper we show that even without moving the laser focus, the void moves upstream a few micrometers after irradiation with subsequent laser pulses in the bulk of calcium fluoride and silica glass. We find that the voids move a maximum distance of approximately 2 μm. We also demonstrate the lateral movement of the void along the axis perpendicular to the beam propagation axis by shifting the focal region of the laser pulses.

2. Experimental Setup

Fig. 1. Schematic of experimental setup for creation by femtosecond laser pulses and in situ observation of voids. ND, HWP, and P denote neutral density filter, half-wave plate, and polarizer, respectively. OB1 and OB2 indicate objective lenses. L1 and L2 indicate lenses.

The experiments were performed with a regeneratively amplified Ti:sapphire laser system (Spectra-Physics, Inc., Hurricane), which produces 130-fs, 800-nm pulses. Figure 1 shows a schematic of the experimental setup. We operated the laser system at a repetition rate of 1 Hz. The beam was magnified by the help of a concave lens L1 with a focal length f of negative 60 mm and a convex lens L2 (f = 300 mm). The central part of the beam was truncated by a circular aperture (diameter, 5 mm) to give uniform spatial profile. The pulse energy was controlled by a half-wave plate and a polarizer. The linearly polarized laser pulses were tightly focused by a high-NA microscope objective to induce localized structural changes or optical damage. We used a 50×, 0.55-NA achromatic objective (Olympus, ULWD MPlan 50). Compensation for the dispersion in the optical system was accomplished by predispersing the pulses with a grating compressor in the amplifier of the laser system. We will report in the following the experiments with 3-mm-thick plate of calcium fluoride at room temperature, however, similar effects were also observed with amorphous silica glass. The four-sides of the samples were optically polished. To visualize sideview of the structural change in situ, optical images of the damages or voids were observed from the direction perpendicular to the optical axis by a transilluminated optical microscope. We used a 50×, 0.55-NA achromatic objective to observe voids in situ. We also made the observation by a 100×, 0.8-NA achromatic objective. Therefore, the spatial resolution of the observing system was approximately several hundred nanometer.

3. Movement of Voids by Irradiation of Laser Pulses

We investigated the movement of voids by changing the number of laser shots under fixed pulse energy. We created voids in the bulk calcium fluoride at a depth of 200 μm beneath the surface. The energy threshold for the observable permanent structural change with the microscope was 386 nJ/pulse by a single shot in the microscope. The threshold for optical breakdown and structural change in bulk calcium fluoride for 100-fs laser pulses has been shown to be around 50 nJ/pulse [11

11. C. B. Schaffer, A. Brodeur, and E. Mazur, “Laser-induced breakdown and damage in bulk transparent materials induced by tightly focused femtosecond laser pulses,” Meas. Sci. Technol. 12, 1784–1794 (2001). [CrossRef]

]. The energy in our experiment exceeds the threshold reported in Ref. 11

11. C. B. Schaffer, A. Brodeur, and E. Mazur, “Laser-induced breakdown and damage in bulk transparent materials induced by tightly focused femtosecond laser pulses,” Meas. Sci. Technol. 12, 1784–1794 (2001). [CrossRef]

by a factor of 6. The possible explanations are is the temporal distortion of femtosecond laser pulses [12

12. Z. Bor, “Distortion of femtosecond laser pulses in lenses and lens systems,” J. Mod. Opt. 35, 1907–1918 (1988). [CrossRef]

,13

13. M. Kempe, U. Stamm, B. Wilhelmi, and W. Rudolph, “Spatial and temporal transformation of femtosecond laser pulses by lenses and lens systems,” J. Opt. Soc. Am. B 9, 1158–1165 (1992). [CrossRef]

], spherical aberration in the focal point, and surface roughness of the polished samples. Figure 2 shows an optical image of movement of voids observed in the yz plane under illumination by unpolarized halogen lamp. The energy was 386 nJ/pulse. The dark spot that was observed in the optical microscope was previously shown to be a cavity or hole [1–3

1. E. N. Glezer, M. Milosavljevic, L. Huang, R. J. Finlay, T.-H. Her, J. P. Callan, and E. Mazur, “Three-dimensional optical storage inside transparent materials,” Opt. Lett. 21, 2023–2025 (1996). [CrossRef] [PubMed]

]. The beam propagation direction of the femtosecond laser pulses (+ z direction) was left to right in the plane of the image. We first created a void by a single shot of the laser pulse and translated the sample along y axis by 10 μm and irradiated two laser pulses at the fresh site. We translated the sample again and increased the number of laser pulse to be irradiated. The number of laser shots was varied from 1 shot to 5 shots. As the number of laser shots increased, the void moved toward -z direction. After structural changes occurs, we observe the scattering light of the laser pulses when subsequent pulses irradiate the sample. Figure 2 shows that the void moved approximately by 2 μm in the -z direction by successive irradiation of laser pulses without shifting the focal point upstream direction. This direction of movement coincides with that of the mechanical translation of a void reported by our group [3

3. W. Watanabe, T. Toma, K. Yamada, J. Nishii, K. Hayashi, and K. Itoh, “Optical seizing and merging of voids in silica glass with infrared femtosecond laser pulses,” Opt. Lett. 25, 1669–1671 (2000). [CrossRef]

]. From the image contrast, the size of a void seems to increase shot by shot. This result is the same when we translated the focal point in Ref. 3

3. W. Watanabe, T. Toma, K. Yamada, J. Nishii, K. Hayashi, and K. Itoh, “Optical seizing and merging of voids in silica glass with infrared femtosecond laser pulses,” Opt. Lett. 25, 1669–1671 (2000). [CrossRef]

. We confirm the void moves in -z direction by successive laser shots.

Fig. 2. Optical movement of a void under irradiation by successive laser shots. Side view of void was observed under illumination unpolarized halogen lamp.

Figure 3 (a) shows the movie of the movement of voids at the energy of 386 nJ/pulse with the number of laser pulses. In Fig. 3, the small circular spot in the left of each figure indicates the absolute position in the images. As we increased the number of laser shots, the shape of void seemed to be elongated along z direction and then the second void was visible around the original location of first void. Figure 3 (b) shows the movement of a void at the energy of 299 nJ/pulse with the number of laser pulses. We set the energy that was incident on the objective lens less than the threshold for the permanent observable structural change. At this energy the structural change was seen after 22 shots. Then the void moved toward the incident direction and the distance of movement terminated after 54 pulses at 1.7 μm. The distance of the movement was plotted every two pulses with three different incident energy in Fig.4. Figure 4 demonstrates that the void moved with the number of laser pulses and that the positions of the void can be controlled within sub-micrometers by changing the number of laser pulses and the energy.

Fig. 3. (2MB) Optical movement of a void under successive irradiation of laser shots. Energy : (a) 386 nJ/pulse and (b) 299 nJ/pulse, respcetively. The small circular spot in the left of each figure indicates the absolute position in the images. The number of shots is indicated upper right. [Media 1] [Media 2]
Fig. 4. Distance of movement of a void. ☐denotes the shape becomes elliptical along the optical axis..

4. Lateral Movement of Voids

We demonstrate, to the best or our knowledge, the lateral movement of a void along the axis perpendicular to the beam propagation axis for the first time. Figures 5 show optical images of movement of voids in CaF2 observed in the yz plane under illumination by a halogen lamp. The energy was 386 nJ/pulse. We created two voids for comparison and set the focal point of the objective lens to the upper in the figure. Then we created a void by a single shot (Fig.5 (a)). We shifted the focal point of the focusing objective along the +y direction by 1 μm and irradiated a laser pulse (Fig. 5 (b)). We repeated the same procedures. The void moves as shown in Fig. 5 (c) and (d). Figures 5 show that the void moves along the axis perpendicular to the beam propagation axis. After the irradiation of five pulses, one spot separated into two. We could not move the void in the + z direction. If we focus the beam at the rear of the void, the beam seriously suffers from scattering owing to the void and the surrounding area. The shift of the focus and the irradiation enables us to change the position of the void three-dimensionally in transparent materials, except pushing forward the void.

Fig. 5. Lateral movement of a void perpendicular to the beam propagation axis. The void moves by 2 μm along the direction perpendicular to optical axis.

5. Conclusion

We demonstrated that irradiation of femtosecond laser pulses move a microscopic bubble inside crystalline calcium fluoride and amorphous silica glass. The microscopic observation revealed that the bubble moves against the direction of propagation of laser pulses as far as 2 microns. This movement is most likely due to the production of easily-ionized defect at the interface of the void. It is likely that easily-ionized defect states, surface state, and color centers that probably produced near the interface cause optical breakdown at the interface for subsequent laser pulses. Once we see that optical breakdown occurs preferentially at this front interface of the void, the void moves upstream direction. We also demonstrated the lateral movement of the void along the axis perpendicular to the beam propagation axis by shifting the laser focus. This movement technique will lead to the 3-D reconfigurable optical storage. The ability to move voids allows fine tuning of optical microstructures that are written within transparent materials.

Acknowledgment

A part of the experiments reported in this paper was conducted at the Venture Business Laboratory, Osaka University. The authors thank D. Kuroda, T. Shinagawa, and K. Yamada of Department of Material and Life Science, Graduate School of Engineering, Osaka University, Yan Li, Venture Business Laboratory, Osaka University and J. Nishii of Photonics Research Institute, Kansai Center, National Institute of Advanced Industrial Science and Technology for helpful discussion.

References and links

1.

E. N. Glezer, M. Milosavljevic, L. Huang, R. J. Finlay, T.-H. Her, J. P. Callan, and E. Mazur, “Three-dimensional optical storage inside transparent materials,” Opt. Lett. 21, 2023–2025 (1996). [CrossRef] [PubMed]

2.

N. Glezer and E. Mazur, “Ultrafast-laser driven micro-explosions in transparent materials,” Appl. Phys. Lett. 71, 882–884 (1997). [CrossRef]

3.

W. Watanabe, T. Toma, K. Yamada, J. Nishii, K. Hayashi, and K. Itoh, “Optical seizing and merging of voids in silica glass with infrared femtosecond laser pulses,” Opt. Lett. 25, 1669–1671 (2000). [CrossRef]

4.

K. M. Davis, K. Miura, N. Sugimoto, and H. Hirao, “Writing waveguides in glass with a femtosecond laser,” Opt. Lett. 21, 1729–1731 (1996). [CrossRef] [PubMed]

5.

K. Miura, J. Qiu, H. Inouye, T. Mitsuyu, and K. Hirao, “Photowritten optical waveguides in various glasses with ultrashort pulse laser,” Appl. Phys. Lett. 71, 3329–3331 (1997). [CrossRef]

6.

K. Yamada, T. Toma, W. Watanabe, J. Nishii, and K. Itoh, “In situ observation of photoinduced refractive index changes in filaments formed in glasses by femtosecond laser pulses,” Opt. Lett. 26, 19–21 (2001). [CrossRef]

7.

C. B. Schaffer, A. Brodeur, J. F. Garca, and E. Mazur, “Micromachining bulk glass by use of femtosecond laser pulses with nanojoule energy,” Opt. Lett. 26, 93–95 (2001). [CrossRef]

8.

D. Homoelle, W. Wielandy, A. L. Gaeta, E. F. Borrelli, and C. Smith, “Infraredphotosensitivity in silica glasses exposed to femtosecondlaser pulses,” Opt. Lett. 24, 1311–1313 (1999). [CrossRef]

9.

L. Sudrie, M. Franco, B. Prade, and A. Mysyrowicz, ”Writing of permanent birefringent microlayers in bulk fused silica with femtosecond laser pulses,“ Opt. Commun. 171, 279–284 (1999). [CrossRef]

10.

A. M. Streltsov and N. F. Borrelli, “Fabrication and analysis of a directional coupler written in glass by nanojoule femtosecond laser pulses,” Opt. Lett. 26, 42–44 (2001). [CrossRef]

11.

C. B. Schaffer, A. Brodeur, and E. Mazur, “Laser-induced breakdown and damage in bulk transparent materials induced by tightly focused femtosecond laser pulses,” Meas. Sci. Technol. 12, 1784–1794 (2001). [CrossRef]

12.

Z. Bor, “Distortion of femtosecond laser pulses in lenses and lens systems,” J. Mod. Opt. 35, 1907–1918 (1988). [CrossRef]

13.

M. Kempe, U. Stamm, B. Wilhelmi, and W. Rudolph, “Spatial and temporal transformation of femtosecond laser pulses by lenses and lens systems,” J. Opt. Soc. Am. B 9, 1158–1165 (1992). [CrossRef]

14.

J. Qiu, K. Miura, and K. Hirao, “Three-dimensional optical memory using glasses as a recording medium through a multi-photon absorption process,” Jpn. J. Appl. Phys. 37, 2263–2266 (1998). [CrossRef]

15.

J. W. Chan, T. Huser, S. Risbud, and D. M. Krol, “Structural changes in fused silica after exposure to focused femtosecond laser pulses,” Opt. Lett. 26, 1726–1728 (2001). [CrossRef]

OCIS Codes
(140.3330) Lasers and laser optics : Laser damage
(140.3440) Lasers and laser optics : Laser-induced breakdown
(190.7110) Nonlinear optics : Ultrafast nonlinear optics
(320.7110) Ultrafast optics : Ultrafast nonlinear optics

ToC Category:
Research Papers

History
Original Manuscript: June 7, 2002
Revised Manuscript: June 25, 2002
Published: July 15, 2002

Citation
Wataru Watanabe and Kazuyoshi Itoh, "Motion of bubble in solid by femtosecond laser pulses," Opt. Express 10, 603-608 (2002)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-10-14-603


Sort:  Journal  |  Reset  

References

  1. E. N. Glezer, M. Milosavljevic, L. Huang, R. J. Finlay, T.-H. Her, J. P. Callan, and E. Mazur, "Three-dimensional optical storage inside transparent materials,�?? Opt. Lett. 21, 2023-2025 (1996). [CrossRef] [PubMed]
  2. N. Glezer and E. Mazur, �??Ultrafast-laser driven micro-explosions in transparent materials,�?? Appl. Phys. Lett. 71, 882-884 (1997). [CrossRef]
  3. W. Watanabe, T. Toma, K. Yamada, J. Nishii, K. Hayashi, and K. Itoh, �??Optical seizing and merging of voids in silica glass with infrared femtosecond laser pulses,�?? Opt. Lett. 25, 1669-1671 (2000). [CrossRef]
  4. K. M. Davis, K. Miura, N. Sugimoto, and H. Hirao, �??Writing waveguides in glass with a femtosecond laser,�?? Opt. Lett. 21, 1729-1731 (1996). [CrossRef] [PubMed]
  5. K. Miura, J. Qiu, H. Inouye, T. Mitsuyu, and K. Hirao, �??Photowritten optical waveguides in various glasses with ultrashort pulse laser,�?? Appl. Phys. Lett. 71, 3329-3331 (1997). [CrossRef]
  6. K. Yamada, T. Toma, W. Watanabe, J. Nishii, and K. Itoh, �??In situ observation of photoinduced refractive index changes in filaments formed in glasses by femtosecond laser pulses,�?? Opt. Lett. 26, 19-21 (2001). [CrossRef]
  7. C. B. Schaffer, A. Brodeur, J. F. Garca, and E. Mazur, �??Micromachining bulk glass by use of femtosecond laser pulses with nanojoule energy,�?? Opt. Lett. 26, 93-95 (2001). [CrossRef]
  8. D. Homoelle, W. Wielandy, A. L. Gaeta, E. F. Borrelli, and C. Smith, �??Infraredphotosensitivity in silica glasses exposed to femtosecondlaser pulses,�?? Opt. Lett. 24, 1311-1313 (1999). [CrossRef]
  9. L. Sudrie, M. Franco, B. Prade, A. Mysyrowicz, �??Writing of permanent birefringent microlayers in bulk fused silica with femtosecond laser pulses,�?? Opt. Commun. 171, 279-284 (1999). [CrossRef]
  10. A. M. Streltsov and N. F. Borrelli, �??Fabrication and analysis of a directional coupler written in glass by nanojoule femtosecond laser pulses,�?? Opt. Lett. 26, 42-44 (2001). [CrossRef]
  11. C. B. Schaffer, A. Brodeur, and E. Mazur, �??Laser-induced breakdown and damage in bulk transparent materials induced by tightly focused femtosecond laser pulses,�?? Meas. Sci. Technol. 12, 1784-1794 (2001). [CrossRef]
  12. Z. Bor, �??Distortion of femtosecond laser pulses in lenses and lens systems,�?? J. Mod. Opt. 35, 1907-1918 (1988). [CrossRef]
  13. M. Kempe, U. Stamm, B. Wilhelmi, and W. Rudolph, �??Spatial and temporal transformation of femtosecond laser pulses by lenses and lens systems,�?? J. Opt. Soc. Am. B 9, 1158-1165 (1992). [CrossRef]
  14. J. Qiu, K. Miura, and K. Hirao, �??Three-dimensional optical memory using glasses as a recording medium through a multi-photon absorption process,�?? Jpn. J. Appl. Phys. 37, 2263-2266 (1998). [CrossRef]
  15. J. W. Chan, T. Huser, S. Risbud, and D. M. Krol, �??Structural changes in fused silica after exposure to focused femtosecond laser pulses,�?? Opt. Lett. 26, 1726-1728 (2001). [CrossRef]

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.

Supplementary Material


» Media 1: AVI (911 KB)     
» Media 2: AVI (911 KB)     

« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited