Abstract

We describe a simple imaging technique that can be used to photograph ultrafast processes with time resolution determined by the duration of pump and probe laser pulses. We demonstrate this technique by photographs having 100-fsec time resolution of a silicon surface undergoing melting and evaporation following intense excitation by an ultrashort laser pulse. These photographs resolve the increase in surface reflectivity caused by surface melting both temporally and spatially. Material evaporation from the melted surface further alters the image of the surface by absorbing and scattering the illuminating laser light. Our analysis of this selectively imaged light suggests that the evaporated material emerges as liquid droplets several hundred angstroms in diameter, which atomize in less than a nanosecond.

© 1985 Optical Society of America

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  1. C. W. White, P. S. Peercy, eds., Laser and Electron Beam Processing of Materials (Academic, New York, 1980).
  2. J. F. Gibbons, L. D. Hess, T. W. Sigmon, eds., Laser and Electron Beam Solid Interactions and Material-Processing (North-Holland, Amsterdam, 1981).
  3. B. R. Appleton, G. K. Celler, eds., Laser and Electron Beam Interactions with Solids, (North-Holland, Amsterdam, 1982).
  4. J. Narayan, W. L. Brown, R. A. Lemons, eds., Laser-Solid Interactions and Transient Thermal Processing of Materials (North-Holland, Amsterdam, 1983).
  5. K. B. Eisenthal, R. M. Hochstrasser, W. Kaiser, A. Lauberau, eds., Picosecond Phenomena III (Springer-Verlag, Berlin, 1982).
    [CrossRef]
  6. D. H. Auston, C. V. Shank, “Picosecond ellipsometry of transient electron–hole plasmas in germanium,” Phys. Rev. Lett. 32, 1120 (1974).
    [CrossRef]
  7. C. V. Shank, R. T. Yen, C. Hirlimann, “Femtosecond time-resolved surface structural dynamics of optically excited silicon,” Phys. Rev. Lett. 51, 900 (1983).
    [CrossRef]
  8. For alternative interpretations, see J. A. Van Vechten, R. Tsui, F. W. Sans, “Non-thermal pulsed laser annealing of Si:plasma annealing,” Phys. Lett. 74A, 422 (1979);see also J. A. Van Vechten, “The gentle electronic nature of pulsed beam annealing, or does it really go superfluid?” in Laser and Electron Beam Interactions with Solids, B. R. Appleton, G. K. Celler, eds. (North-Holland, Amsterdam, 1982), pp. 49–60.
  9. C. V. Shank, R. Yen, C. Hirlimann, “Time-resolved reflectivity measurements of femtosecond optical-pulse-induced phase transitions in silicon,” Phys. Rev. Lett. 50, 454 (1983).
    [CrossRef]
  10. R. L. Fork, B. I. Greene, C. V. Shank, “Generation of optical pulses shorter than 0.1 psec by colliding pulse mode locking,” Appl. Phys. Lett. 38, 671 (1981).
    [CrossRef]
  11. R. L. Fork, C. V. Shank, R. Yen, “Amplification of 70-fs optical pulses to gigawatt powers,” Appl. Phys. Lett. 41, 223 (1982).
    [CrossRef]
  12. R. L. Fork, C. V. Shank, C. Hirlimann, R. Yen, W. J. Tomlinson, “Femtosecond white-light continuum pulses,” Opt. Lett. 8, 1 (1983).
    [CrossRef] [PubMed]
  13. R. Yen, J. M. Liu, H. Kurz, N. Bloembergen, “Space–time resolved reflectivity measurements of picosecond laser induced phase transitions in [111] silicon,” in Laser and Electron Beam Interactions with Solids, B. R. Appleton, G. K. Celler, eds. (North-Holland, Amsterdam, 1982), pp. 37–42.
  14. J. M. Liu, R. Yen, H. Kurz, N. Bloembergen, “Phase transformation on and charged particle emission from a silicon crystal surface, induced by picosecond laser pulses,” Appl. Phys. Lett. 39, 755 (1981).
    [CrossRef]
  15. M. Hanabusa, M. Suzuki, S. Nishigaki, “Dynamics of laser-induced vaporization for ultrafast deposition of amorphous silicon films,” Appl. Phys. Lett. 38, 385 (1981).
    [CrossRef]
  16. B. Stritzker, A. Pospieszczyk, J. A. Tagle, “Measurement of lattice temperature of silicon during pulsed laser annealing,” Phys. Rev. Lett. 47, 356 (1981).
    [CrossRef]
  17. H. C. van de Hulst, Light Scattering by Small Particles (Dover, New York, 1981), Chap. 4.
  18. J. M. Liu, “Thermal model of picosecond laser interactions with silicon,” Ph.D. dissertation (Harvard University, Cambridge, Mass., 1982).

1983 (3)

C. V. Shank, R. T. Yen, C. Hirlimann, “Femtosecond time-resolved surface structural dynamics of optically excited silicon,” Phys. Rev. Lett. 51, 900 (1983).
[CrossRef]

C. V. Shank, R. Yen, C. Hirlimann, “Time-resolved reflectivity measurements of femtosecond optical-pulse-induced phase transitions in silicon,” Phys. Rev. Lett. 50, 454 (1983).
[CrossRef]

R. L. Fork, C. V. Shank, C. Hirlimann, R. Yen, W. J. Tomlinson, “Femtosecond white-light continuum pulses,” Opt. Lett. 8, 1 (1983).
[CrossRef] [PubMed]

1982 (1)

R. L. Fork, C. V. Shank, R. Yen, “Amplification of 70-fs optical pulses to gigawatt powers,” Appl. Phys. Lett. 41, 223 (1982).
[CrossRef]

1981 (4)

J. M. Liu, R. Yen, H. Kurz, N. Bloembergen, “Phase transformation on and charged particle emission from a silicon crystal surface, induced by picosecond laser pulses,” Appl. Phys. Lett. 39, 755 (1981).
[CrossRef]

M. Hanabusa, M. Suzuki, S. Nishigaki, “Dynamics of laser-induced vaporization for ultrafast deposition of amorphous silicon films,” Appl. Phys. Lett. 38, 385 (1981).
[CrossRef]

B. Stritzker, A. Pospieszczyk, J. A. Tagle, “Measurement of lattice temperature of silicon during pulsed laser annealing,” Phys. Rev. Lett. 47, 356 (1981).
[CrossRef]

R. L. Fork, B. I. Greene, C. V. Shank, “Generation of optical pulses shorter than 0.1 psec by colliding pulse mode locking,” Appl. Phys. Lett. 38, 671 (1981).
[CrossRef]

1979 (1)

For alternative interpretations, see J. A. Van Vechten, R. Tsui, F. W. Sans, “Non-thermal pulsed laser annealing of Si:plasma annealing,” Phys. Lett. 74A, 422 (1979);see also J. A. Van Vechten, “The gentle electronic nature of pulsed beam annealing, or does it really go superfluid?” in Laser and Electron Beam Interactions with Solids, B. R. Appleton, G. K. Celler, eds. (North-Holland, Amsterdam, 1982), pp. 49–60.

1974 (1)

D. H. Auston, C. V. Shank, “Picosecond ellipsometry of transient electron–hole plasmas in germanium,” Phys. Rev. Lett. 32, 1120 (1974).
[CrossRef]

Auston, D. H.

D. H. Auston, C. V. Shank, “Picosecond ellipsometry of transient electron–hole plasmas in germanium,” Phys. Rev. Lett. 32, 1120 (1974).
[CrossRef]

Bloembergen, N.

J. M. Liu, R. Yen, H. Kurz, N. Bloembergen, “Phase transformation on and charged particle emission from a silicon crystal surface, induced by picosecond laser pulses,” Appl. Phys. Lett. 39, 755 (1981).
[CrossRef]

R. Yen, J. M. Liu, H. Kurz, N. Bloembergen, “Space–time resolved reflectivity measurements of picosecond laser induced phase transitions in [111] silicon,” in Laser and Electron Beam Interactions with Solids, B. R. Appleton, G. K. Celler, eds. (North-Holland, Amsterdam, 1982), pp. 37–42.

Fork, R. L.

R. L. Fork, C. V. Shank, C. Hirlimann, R. Yen, W. J. Tomlinson, “Femtosecond white-light continuum pulses,” Opt. Lett. 8, 1 (1983).
[CrossRef] [PubMed]

R. L. Fork, C. V. Shank, R. Yen, “Amplification of 70-fs optical pulses to gigawatt powers,” Appl. Phys. Lett. 41, 223 (1982).
[CrossRef]

R. L. Fork, B. I. Greene, C. V. Shank, “Generation of optical pulses shorter than 0.1 psec by colliding pulse mode locking,” Appl. Phys. Lett. 38, 671 (1981).
[CrossRef]

Greene, B. I.

R. L. Fork, B. I. Greene, C. V. Shank, “Generation of optical pulses shorter than 0.1 psec by colliding pulse mode locking,” Appl. Phys. Lett. 38, 671 (1981).
[CrossRef]

Hanabusa, M.

M. Hanabusa, M. Suzuki, S. Nishigaki, “Dynamics of laser-induced vaporization for ultrafast deposition of amorphous silicon films,” Appl. Phys. Lett. 38, 385 (1981).
[CrossRef]

Hirlimann, C.

R. L. Fork, C. V. Shank, C. Hirlimann, R. Yen, W. J. Tomlinson, “Femtosecond white-light continuum pulses,” Opt. Lett. 8, 1 (1983).
[CrossRef] [PubMed]

C. V. Shank, R. Yen, C. Hirlimann, “Time-resolved reflectivity measurements of femtosecond optical-pulse-induced phase transitions in silicon,” Phys. Rev. Lett. 50, 454 (1983).
[CrossRef]

C. V. Shank, R. T. Yen, C. Hirlimann, “Femtosecond time-resolved surface structural dynamics of optically excited silicon,” Phys. Rev. Lett. 51, 900 (1983).
[CrossRef]

Kurz, H.

J. M. Liu, R. Yen, H. Kurz, N. Bloembergen, “Phase transformation on and charged particle emission from a silicon crystal surface, induced by picosecond laser pulses,” Appl. Phys. Lett. 39, 755 (1981).
[CrossRef]

R. Yen, J. M. Liu, H. Kurz, N. Bloembergen, “Space–time resolved reflectivity measurements of picosecond laser induced phase transitions in [111] silicon,” in Laser and Electron Beam Interactions with Solids, B. R. Appleton, G. K. Celler, eds. (North-Holland, Amsterdam, 1982), pp. 37–42.

Liu, J. M.

J. M. Liu, R. Yen, H. Kurz, N. Bloembergen, “Phase transformation on and charged particle emission from a silicon crystal surface, induced by picosecond laser pulses,” Appl. Phys. Lett. 39, 755 (1981).
[CrossRef]

R. Yen, J. M. Liu, H. Kurz, N. Bloembergen, “Space–time resolved reflectivity measurements of picosecond laser induced phase transitions in [111] silicon,” in Laser and Electron Beam Interactions with Solids, B. R. Appleton, G. K. Celler, eds. (North-Holland, Amsterdam, 1982), pp. 37–42.

J. M. Liu, “Thermal model of picosecond laser interactions with silicon,” Ph.D. dissertation (Harvard University, Cambridge, Mass., 1982).

Nishigaki, S.

M. Hanabusa, M. Suzuki, S. Nishigaki, “Dynamics of laser-induced vaporization for ultrafast deposition of amorphous silicon films,” Appl. Phys. Lett. 38, 385 (1981).
[CrossRef]

Pospieszczyk, A.

B. Stritzker, A. Pospieszczyk, J. A. Tagle, “Measurement of lattice temperature of silicon during pulsed laser annealing,” Phys. Rev. Lett. 47, 356 (1981).
[CrossRef]

Sans, F. W.

For alternative interpretations, see J. A. Van Vechten, R. Tsui, F. W. Sans, “Non-thermal pulsed laser annealing of Si:plasma annealing,” Phys. Lett. 74A, 422 (1979);see also J. A. Van Vechten, “The gentle electronic nature of pulsed beam annealing, or does it really go superfluid?” in Laser and Electron Beam Interactions with Solids, B. R. Appleton, G. K. Celler, eds. (North-Holland, Amsterdam, 1982), pp. 49–60.

Shank, C. V.

C. V. Shank, R. Yen, C. Hirlimann, “Time-resolved reflectivity measurements of femtosecond optical-pulse-induced phase transitions in silicon,” Phys. Rev. Lett. 50, 454 (1983).
[CrossRef]

C. V. Shank, R. T. Yen, C. Hirlimann, “Femtosecond time-resolved surface structural dynamics of optically excited silicon,” Phys. Rev. Lett. 51, 900 (1983).
[CrossRef]

R. L. Fork, C. V. Shank, C. Hirlimann, R. Yen, W. J. Tomlinson, “Femtosecond white-light continuum pulses,” Opt. Lett. 8, 1 (1983).
[CrossRef] [PubMed]

R. L. Fork, C. V. Shank, R. Yen, “Amplification of 70-fs optical pulses to gigawatt powers,” Appl. Phys. Lett. 41, 223 (1982).
[CrossRef]

R. L. Fork, B. I. Greene, C. V. Shank, “Generation of optical pulses shorter than 0.1 psec by colliding pulse mode locking,” Appl. Phys. Lett. 38, 671 (1981).
[CrossRef]

D. H. Auston, C. V. Shank, “Picosecond ellipsometry of transient electron–hole plasmas in germanium,” Phys. Rev. Lett. 32, 1120 (1974).
[CrossRef]

Stritzker, B.

B. Stritzker, A. Pospieszczyk, J. A. Tagle, “Measurement of lattice temperature of silicon during pulsed laser annealing,” Phys. Rev. Lett. 47, 356 (1981).
[CrossRef]

Suzuki, M.

M. Hanabusa, M. Suzuki, S. Nishigaki, “Dynamics of laser-induced vaporization for ultrafast deposition of amorphous silicon films,” Appl. Phys. Lett. 38, 385 (1981).
[CrossRef]

Tagle, J. A.

B. Stritzker, A. Pospieszczyk, J. A. Tagle, “Measurement of lattice temperature of silicon during pulsed laser annealing,” Phys. Rev. Lett. 47, 356 (1981).
[CrossRef]

Tomlinson, W. J.

Tsui, R.

For alternative interpretations, see J. A. Van Vechten, R. Tsui, F. W. Sans, “Non-thermal pulsed laser annealing of Si:plasma annealing,” Phys. Lett. 74A, 422 (1979);see also J. A. Van Vechten, “The gentle electronic nature of pulsed beam annealing, or does it really go superfluid?” in Laser and Electron Beam Interactions with Solids, B. R. Appleton, G. K. Celler, eds. (North-Holland, Amsterdam, 1982), pp. 49–60.

van de Hulst, H. C.

H. C. van de Hulst, Light Scattering by Small Particles (Dover, New York, 1981), Chap. 4.

Van Vechten, J. A.

For alternative interpretations, see J. A. Van Vechten, R. Tsui, F. W. Sans, “Non-thermal pulsed laser annealing of Si:plasma annealing,” Phys. Lett. 74A, 422 (1979);see also J. A. Van Vechten, “The gentle electronic nature of pulsed beam annealing, or does it really go superfluid?” in Laser and Electron Beam Interactions with Solids, B. R. Appleton, G. K. Celler, eds. (North-Holland, Amsterdam, 1982), pp. 49–60.

Yen, R.

C. V. Shank, R. Yen, C. Hirlimann, “Time-resolved reflectivity measurements of femtosecond optical-pulse-induced phase transitions in silicon,” Phys. Rev. Lett. 50, 454 (1983).
[CrossRef]

R. L. Fork, C. V. Shank, C. Hirlimann, R. Yen, W. J. Tomlinson, “Femtosecond white-light continuum pulses,” Opt. Lett. 8, 1 (1983).
[CrossRef] [PubMed]

R. L. Fork, C. V. Shank, R. Yen, “Amplification of 70-fs optical pulses to gigawatt powers,” Appl. Phys. Lett. 41, 223 (1982).
[CrossRef]

J. M. Liu, R. Yen, H. Kurz, N. Bloembergen, “Phase transformation on and charged particle emission from a silicon crystal surface, induced by picosecond laser pulses,” Appl. Phys. Lett. 39, 755 (1981).
[CrossRef]

R. Yen, J. M. Liu, H. Kurz, N. Bloembergen, “Space–time resolved reflectivity measurements of picosecond laser induced phase transitions in [111] silicon,” in Laser and Electron Beam Interactions with Solids, B. R. Appleton, G. K. Celler, eds. (North-Holland, Amsterdam, 1982), pp. 37–42.

Yen, R. T.

C. V. Shank, R. T. Yen, C. Hirlimann, “Femtosecond time-resolved surface structural dynamics of optically excited silicon,” Phys. Rev. Lett. 51, 900 (1983).
[CrossRef]

Appl. Phys. Lett. (4)

R. L. Fork, B. I. Greene, C. V. Shank, “Generation of optical pulses shorter than 0.1 psec by colliding pulse mode locking,” Appl. Phys. Lett. 38, 671 (1981).
[CrossRef]

R. L. Fork, C. V. Shank, R. Yen, “Amplification of 70-fs optical pulses to gigawatt powers,” Appl. Phys. Lett. 41, 223 (1982).
[CrossRef]

J. M. Liu, R. Yen, H. Kurz, N. Bloembergen, “Phase transformation on and charged particle emission from a silicon crystal surface, induced by picosecond laser pulses,” Appl. Phys. Lett. 39, 755 (1981).
[CrossRef]

M. Hanabusa, M. Suzuki, S. Nishigaki, “Dynamics of laser-induced vaporization for ultrafast deposition of amorphous silicon films,” Appl. Phys. Lett. 38, 385 (1981).
[CrossRef]

Opt. Lett. (1)

Phys. Lett. (1)

For alternative interpretations, see J. A. Van Vechten, R. Tsui, F. W. Sans, “Non-thermal pulsed laser annealing of Si:plasma annealing,” Phys. Lett. 74A, 422 (1979);see also J. A. Van Vechten, “The gentle electronic nature of pulsed beam annealing, or does it really go superfluid?” in Laser and Electron Beam Interactions with Solids, B. R. Appleton, G. K. Celler, eds. (North-Holland, Amsterdam, 1982), pp. 49–60.

Phys. Rev. Lett. (4)

C. V. Shank, R. Yen, C. Hirlimann, “Time-resolved reflectivity measurements of femtosecond optical-pulse-induced phase transitions in silicon,” Phys. Rev. Lett. 50, 454 (1983).
[CrossRef]

D. H. Auston, C. V. Shank, “Picosecond ellipsometry of transient electron–hole plasmas in germanium,” Phys. Rev. Lett. 32, 1120 (1974).
[CrossRef]

C. V. Shank, R. T. Yen, C. Hirlimann, “Femtosecond time-resolved surface structural dynamics of optically excited silicon,” Phys. Rev. Lett. 51, 900 (1983).
[CrossRef]

B. Stritzker, A. Pospieszczyk, J. A. Tagle, “Measurement of lattice temperature of silicon during pulsed laser annealing,” Phys. Rev. Lett. 47, 356 (1981).
[CrossRef]

Other (8)

H. C. van de Hulst, Light Scattering by Small Particles (Dover, New York, 1981), Chap. 4.

J. M. Liu, “Thermal model of picosecond laser interactions with silicon,” Ph.D. dissertation (Harvard University, Cambridge, Mass., 1982).

R. Yen, J. M. Liu, H. Kurz, N. Bloembergen, “Space–time resolved reflectivity measurements of picosecond laser induced phase transitions in [111] silicon,” in Laser and Electron Beam Interactions with Solids, B. R. Appleton, G. K. Celler, eds. (North-Holland, Amsterdam, 1982), pp. 37–42.

C. W. White, P. S. Peercy, eds., Laser and Electron Beam Processing of Materials (Academic, New York, 1980).

J. F. Gibbons, L. D. Hess, T. W. Sigmon, eds., Laser and Electron Beam Solid Interactions and Material-Processing (North-Holland, Amsterdam, 1981).

B. R. Appleton, G. K. Celler, eds., Laser and Electron Beam Interactions with Solids, (North-Holland, Amsterdam, 1982).

J. Narayan, W. L. Brown, R. A. Lemons, eds., Laser-Solid Interactions and Transient Thermal Processing of Materials (North-Holland, Amsterdam, 1983).

K. B. Eisenthal, R. M. Hochstrasser, W. Kaiser, A. Lauberau, eds., Picosecond Phenomena III (Springer-Verlag, Berlin, 1982).
[CrossRef]

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Figures (3)

Fig. 1
Fig. 1

Experimental arrangement used to obtain femtosecond time-resolved photographic images of a silicon surface undergoing ultrafast phase transitions.

Fig. 2
Fig. 2

Time-resolved photographs of a silicon [111] surface following photoexcitation by an 80-fsec optical pulse of 0.5 J/cm2. Numbers indicate pump–probe optical delay in picoseconds. Note the rapid appearance of the highly reflective molten silicon [b)–d)], followed by the ejection and dissipation of evaporated material [dark central spot in e)–h)].

Fig. 3
Fig. 3

Measured fraction of probe intensity transmitted through the cloud of material that forms above a silicon surface following intense photoexcitation, plotted as a function of probe wavelength for three pump–probe time delays: Δt = 50 psec (filled circles), 300 psec (×’s), and 550 psec (open circles). Dashed lines are theoretical curves based on absorption by small (a < 250 Å) conducting spherical droplets of liquid silicon, where the depth parameter l (see text) is 1400 Å (300 psec) and 400 Å (550 psec). The dotted line for the Δt = 50-psec case is a theoretical curve for which larger spheres (a ∼ 700 Å), which introduce significant scattering, have been assumed.

Equations (3)

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I t = I 0 exp [ 2 σ ext ( λ ) NL ] ,
σ ext ( λ ) = π a 2 ( 8 π a λ Im m 2 1 m 2 + 2 + 128 π 4 a 4 3 λ 4 | m 2 1 m 2 + 2 | 2 )
2 σ ext ( λ ) NL = 4 π l λ [ 3 π Im m 2 1 m 2 + 2 + 2 ( 2 π a λ ) 3 | m 2 1 m 2 + 2 | ] 2

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