Abstract

Imaging with ultrashort exposure times is generally achieved with a crossed-beam geometry. In the usual arrangement, an off-axis gating pulse induces birefringence in a medium exhibiting a strong Kerr response (commonly carbon disulfide) which is followed by a polarizer aligned to fully attenuate the on-axis imaging beam. By properly timing the gate pulse, imaging light experiences a polarization change allowing time-dependent transmission through the polarizer to form an ultrashort image. The crossed-beam system is effective in generating short gate times, however, signal transmission through the system is complicated by the crossing angle of the gate and imaging beams. This work presents a robust ultrafast time-gated imaging scheme based on a combination of type-I frequency doubling and a collinear optical arrangement in carbon disulfide. We discuss spatial effects arising from crossed-beam Kerr gating, and examine the imaging spatial resolution and transmission timing affected by collinear activation of the Kerr medium, which eliminates crossing angle spatial effects and produces gate times on the order of 1 ps. In addition, the collinear, two-color system is applied to image structure in an optical fiber and a gasoline fuel spray, in order to demonstrate image formation utilizing ballistic or refracted light, selected on the basis of its transmission time.

© 2014 Optical Society of America

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References

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  1. R. R. Alfano, S. G. Demos, and S. K. Gayen, “Advances in optical imaging of biomedical media,” Ann. N. Y. Acad. Sci.820, 248–271 (1997).
    [CrossRef] [PubMed]
  2. L. Wang, Y. Liu, P. P. Ho, and R. R. Alfano, “Ballistic imaging of biomedical samples using picosecond optical Kerr gate,” Proc. SPIE1431, 97–101 (1991).
    [CrossRef]
  3. M. Linne, “Imaging in the optically dense regions of a spray: A review of developing techniques,” Prog. Energ. Combust.39, 403–440 (2013).
    [CrossRef]
  4. E. Berrocal, D. L. Sedarsky, M. E. Paciaroni, I. V. Meglinski, and M. A. Linne, “Laser light scattering in turbid media Part I: Experimental and simulated results for the spatial intensity distribution,” Opt. Express15, 10649–10665 (2007).
    [CrossRef] [PubMed]
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    [CrossRef]
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    [CrossRef] [PubMed]
  7. D. Newns, B. Elmegreen, X. Hu Liu, and G. Martyna, “A low-voltage high-speed electronic switch based on piezoelectric transduction,” J. Appl. Phys.111, 084509 (2012).
    [CrossRef]
  8. M. D. Duncan, R. Mahon, L. L. Tankersley, and J. Reintjes, “Time-gated imaging through scattering media using stimulated Raman amplification,” Opt. Lett.16, 1868–1870 (1991).
    [CrossRef] [PubMed]
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    [CrossRef] [PubMed]
  10. S. Idlahcen, C. Rozé, L. Méès, T. Girasole, and J.-B. Blaisot, “Sub-picosecond ballistic imaging of a liquid jet,” Exp. Fluids52, 289–298 (2011).
    [CrossRef]
  11. L. Wang, P. Ho, C. Liu, G. Zhang, and R. Alfano, “Ballistic 2-d imaging through scattering walls using an ultrafast optical Kerr gate,” Science253, 769–771 (1991).
    [CrossRef] [PubMed]
  12. R. Alfano, ed., Semiconductors probed by ultrafast laser spectroscopy (Academic, 1984), Vol. II.
  13. W. Tan, Y. Yang, J. Si, J. Tong, W. Yi, F. Chen, and X. Hou, “Shape measurement of objects using an ultrafast optical Kerr gate of Bismuth glass,” J. Appl. Phys.107, 043104 (2010).
    [CrossRef]
  14. I. A. Heisler, R. R. B. Correia, T. Buckup, S. L. S. Cunha, and N. P. da Silveira, “Time-resolved optical Kerr-effect investigation on CS2/polystyrene mixtures,” J. Chem. Phys.123, 054509 (2005).
    [CrossRef] [PubMed]
  15. J.-Y. Tong, W.-J. Tan, J.-H. Si, F. Chen, W.-H. Yi, and X. Hou, “High Time-resolved imaging of targets in turbid media using ultrafast optical Kerr gate,” Chinese Phys. Lett.29, 024207 (2012).
    [CrossRef]
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    [CrossRef]
  17. International Standard ISO 12233, Photography - Electronic still-picture cameras - Resolution measurement, ISO, 2000.
  18. T. Li, H. Feng, Z. Xu, X. Li, Z. Cen, and Q. Li, “Comparison of different analytical edge spread function models for MTF calculation using curve-fitting,” Proc. SPIE7498, 74981H (2009).
    [CrossRef]

2013 (1)

M. Linne, “Imaging in the optically dense regions of a spray: A review of developing techniques,” Prog. Energ. Combust.39, 403–440 (2013).
[CrossRef]

2012 (2)

J.-Y. Tong, W.-J. Tan, J.-H. Si, F. Chen, W.-H. Yi, and X. Hou, “High Time-resolved imaging of targets in turbid media using ultrafast optical Kerr gate,” Chinese Phys. Lett.29, 024207 (2012).
[CrossRef]

D. Newns, B. Elmegreen, X. Hu Liu, and G. Martyna, “A low-voltage high-speed electronic switch based on piezoelectric transduction,” J. Appl. Phys.111, 084509 (2012).
[CrossRef]

2011 (1)

S. Idlahcen, C. Rozé, L. Méès, T. Girasole, and J.-B. Blaisot, “Sub-picosecond ballistic imaging of a liquid jet,” Exp. Fluids52, 289–298 (2011).
[CrossRef]

2010 (1)

W. Tan, Y. Yang, J. Si, J. Tong, W. Yi, F. Chen, and X. Hou, “Shape measurement of objects using an ultrafast optical Kerr gate of Bismuth glass,” J. Appl. Phys.107, 043104 (2010).
[CrossRef]

2009 (3)

2008 (1)

2007 (1)

2005 (1)

I. A. Heisler, R. R. B. Correia, T. Buckup, S. L. S. Cunha, and N. P. da Silveira, “Time-resolved optical Kerr-effect investigation on CS2/polystyrene mixtures,” J. Chem. Phys.123, 054509 (2005).
[CrossRef] [PubMed]

1997 (1)

R. R. Alfano, S. G. Demos, and S. K. Gayen, “Advances in optical imaging of biomedical media,” Ann. N. Y. Acad. Sci.820, 248–271 (1997).
[CrossRef] [PubMed]

1991 (4)

L. Wang, Y. Liu, P. P. Ho, and R. R. Alfano, “Ballistic imaging of biomedical samples using picosecond optical Kerr gate,” Proc. SPIE1431, 97–101 (1991).
[CrossRef]

L. Wang, P. Ho, C. Liu, G. Zhang, and R. Alfano, “Ballistic 2-d imaging through scattering walls using an ultrafast optical Kerr gate,” Science253, 769–771 (1991).
[CrossRef] [PubMed]

K. M. Yoo, Q. Xing, and R. R. Alfano, “Imaging objects hidden in highly scattering media using femtosecond second-harmonic-generation cross-correlation time gating,” Opt. Lett.16, 1019–1021 (1991).
[CrossRef] [PubMed]

M. D. Duncan, R. Mahon, L. L. Tankersley, and J. Reintjes, “Time-gated imaging through scattering media using stimulated Raman amplification,” Opt. Lett.16, 1868–1870 (1991).
[CrossRef] [PubMed]

Alfano, R.

L. Wang, P. Ho, C. Liu, G. Zhang, and R. Alfano, “Ballistic 2-d imaging through scattering walls using an ultrafast optical Kerr gate,” Science253, 769–771 (1991).
[CrossRef] [PubMed]

Alfano, R. R.

R. R. Alfano, S. G. Demos, and S. K. Gayen, “Advances in optical imaging of biomedical media,” Ann. N. Y. Acad. Sci.820, 248–271 (1997).
[CrossRef] [PubMed]

L. Wang, Y. Liu, P. P. Ho, and R. R. Alfano, “Ballistic imaging of biomedical samples using picosecond optical Kerr gate,” Proc. SPIE1431, 97–101 (1991).
[CrossRef]

K. M. Yoo, Q. Xing, and R. R. Alfano, “Imaging objects hidden in highly scattering media using femtosecond second-harmonic-generation cross-correlation time gating,” Opt. Lett.16, 1019–1021 (1991).
[CrossRef] [PubMed]

Berrocal, E.

Blaisot, J.-B.

S. Idlahcen, C. Rozé, L. Méès, T. Girasole, and J.-B. Blaisot, “Sub-picosecond ballistic imaging of a liquid jet,” Exp. Fluids52, 289–298 (2011).
[CrossRef]

S. Idlahcen, L. Méès, C. Rozé, T. Girasole, and J.-B. Blaisot, “Time gate, optical layout, and wavelength effects on ballistic imaging,” J. Opt. Soc. Am. A26, 1995–2004 (2009).
[CrossRef]

Buckup, T.

I. A. Heisler, R. R. B. Correia, T. Buckup, S. L. S. Cunha, and N. P. da Silveira, “Time-resolved optical Kerr-effect investigation on CS2/polystyrene mixtures,” J. Chem. Phys.123, 054509 (2005).
[CrossRef] [PubMed]

Calba, C.

Cen, Z.

T. Li, H. Feng, Z. Xu, X. Li, Z. Cen, and Q. Li, “Comparison of different analytical edge spread function models for MTF calculation using curve-fitting,” Proc. SPIE7498, 74981H (2009).
[CrossRef]

Chen, F.

J.-Y. Tong, W.-J. Tan, J.-H. Si, F. Chen, W.-H. Yi, and X. Hou, “High Time-resolved imaging of targets in turbid media using ultrafast optical Kerr gate,” Chinese Phys. Lett.29, 024207 (2012).
[CrossRef]

W. Tan, Y. Yang, J. Si, J. Tong, W. Yi, F. Chen, and X. Hou, “Shape measurement of objects using an ultrafast optical Kerr gate of Bismuth glass,” J. Appl. Phys.107, 043104 (2010).
[CrossRef]

Correia, R. R. B.

I. A. Heisler, R. R. B. Correia, T. Buckup, S. L. S. Cunha, and N. P. da Silveira, “Time-resolved optical Kerr-effect investigation on CS2/polystyrene mixtures,” J. Chem. Phys.123, 054509 (2005).
[CrossRef] [PubMed]

Cunha, S. L. S.

I. A. Heisler, R. R. B. Correia, T. Buckup, S. L. S. Cunha, and N. P. da Silveira, “Time-resolved optical Kerr-effect investigation on CS2/polystyrene mixtures,” J. Chem. Phys.123, 054509 (2005).
[CrossRef] [PubMed]

da Silveira, N. P.

I. A. Heisler, R. R. B. Correia, T. Buckup, S. L. S. Cunha, and N. P. da Silveira, “Time-resolved optical Kerr-effect investigation on CS2/polystyrene mixtures,” J. Chem. Phys.123, 054509 (2005).
[CrossRef] [PubMed]

Demos, S. G.

R. R. Alfano, S. G. Demos, and S. K. Gayen, “Advances in optical imaging of biomedical media,” Ann. N. Y. Acad. Sci.820, 248–271 (1997).
[CrossRef] [PubMed]

Duncan, M. D.

Elmegreen, B.

D. Newns, B. Elmegreen, X. Hu Liu, and G. Martyna, “A low-voltage high-speed electronic switch based on piezoelectric transduction,” J. Appl. Phys.111, 084509 (2012).
[CrossRef]

Feng, H.

T. Li, H. Feng, Z. Xu, X. Li, Z. Cen, and Q. Li, “Comparison of different analytical edge spread function models for MTF calculation using curve-fitting,” Proc. SPIE7498, 74981H (2009).
[CrossRef]

Gayen, S. K.

R. R. Alfano, S. G. Demos, and S. K. Gayen, “Advances in optical imaging of biomedical media,” Ann. N. Y. Acad. Sci.820, 248–271 (1997).
[CrossRef] [PubMed]

Girasole, T.

Heisler, I. A.

I. A. Heisler, R. R. B. Correia, T. Buckup, S. L. S. Cunha, and N. P. da Silveira, “Time-resolved optical Kerr-effect investigation on CS2/polystyrene mixtures,” J. Chem. Phys.123, 054509 (2005).
[CrossRef] [PubMed]

Ho, P.

L. Wang, P. Ho, C. Liu, G. Zhang, and R. Alfano, “Ballistic 2-d imaging through scattering walls using an ultrafast optical Kerr gate,” Science253, 769–771 (1991).
[CrossRef] [PubMed]

Ho, P. P.

L. Wang, Y. Liu, P. P. Ho, and R. R. Alfano, “Ballistic imaging of biomedical samples using picosecond optical Kerr gate,” Proc. SPIE1431, 97–101 (1991).
[CrossRef]

Hou, X.

J.-Y. Tong, W.-J. Tan, J.-H. Si, F. Chen, W.-H. Yi, and X. Hou, “High Time-resolved imaging of targets in turbid media using ultrafast optical Kerr gate,” Chinese Phys. Lett.29, 024207 (2012).
[CrossRef]

W. Tan, Y. Yang, J. Si, J. Tong, W. Yi, F. Chen, and X. Hou, “Shape measurement of objects using an ultrafast optical Kerr gate of Bismuth glass,” J. Appl. Phys.107, 043104 (2010).
[CrossRef]

Hu Liu, X.

D. Newns, B. Elmegreen, X. Hu Liu, and G. Martyna, “A low-voltage high-speed electronic switch based on piezoelectric transduction,” J. Appl. Phys.111, 084509 (2012).
[CrossRef]

Idlahcen, S.

S. Idlahcen, C. Rozé, L. Méès, T. Girasole, and J.-B. Blaisot, “Sub-picosecond ballistic imaging of a liquid jet,” Exp. Fluids52, 289–298 (2011).
[CrossRef]

S. Idlahcen, L. Méès, C. Rozé, T. Girasole, and J.-B. Blaisot, “Time gate, optical layout, and wavelength effects on ballistic imaging,” J. Opt. Soc. Am. A26, 1995–2004 (2009).
[CrossRef]

Li, Q.

T. Li, H. Feng, Z. Xu, X. Li, Z. Cen, and Q. Li, “Comparison of different analytical edge spread function models for MTF calculation using curve-fitting,” Proc. SPIE7498, 74981H (2009).
[CrossRef]

Li, T.

T. Li, H. Feng, Z. Xu, X. Li, Z. Cen, and Q. Li, “Comparison of different analytical edge spread function models for MTF calculation using curve-fitting,” Proc. SPIE7498, 74981H (2009).
[CrossRef]

Li, X.

T. Li, H. Feng, Z. Xu, X. Li, Z. Cen, and Q. Li, “Comparison of different analytical edge spread function models for MTF calculation using curve-fitting,” Proc. SPIE7498, 74981H (2009).
[CrossRef]

Linne, M.

M. Linne, “Imaging in the optically dense regions of a spray: A review of developing techniques,” Prog. Energ. Combust.39, 403–440 (2013).
[CrossRef]

Linne, M. A.

Liu, C.

L. Wang, P. Ho, C. Liu, G. Zhang, and R. Alfano, “Ballistic 2-d imaging through scattering walls using an ultrafast optical Kerr gate,” Science253, 769–771 (1991).
[CrossRef] [PubMed]

Liu, Y.

L. Wang, Y. Liu, P. P. Ho, and R. R. Alfano, “Ballistic imaging of biomedical samples using picosecond optical Kerr gate,” Proc. SPIE1431, 97–101 (1991).
[CrossRef]

Mahon, R.

Martyna, G.

D. Newns, B. Elmegreen, X. Hu Liu, and G. Martyna, “A low-voltage high-speed electronic switch based on piezoelectric transduction,” J. Appl. Phys.111, 084509 (2012).
[CrossRef]

Méès, L.

Meglinski, I. V.

Newns, D.

D. Newns, B. Elmegreen, X. Hu Liu, and G. Martyna, “A low-voltage high-speed electronic switch based on piezoelectric transduction,” J. Appl. Phys.111, 084509 (2012).
[CrossRef]

Paciaroni, M. E.

Reintjes, J.

Rozé, C.

Sedarsky, D. L.

Si, J.

W. Tan, Y. Yang, J. Si, J. Tong, W. Yi, F. Chen, and X. Hou, “Shape measurement of objects using an ultrafast optical Kerr gate of Bismuth glass,” J. Appl. Phys.107, 043104 (2010).
[CrossRef]

Si, J.-H.

J.-Y. Tong, W.-J. Tan, J.-H. Si, F. Chen, W.-H. Yi, and X. Hou, “High Time-resolved imaging of targets in turbid media using ultrafast optical Kerr gate,” Chinese Phys. Lett.29, 024207 (2012).
[CrossRef]

Tan, W.

W. Tan, Y. Yang, J. Si, J. Tong, W. Yi, F. Chen, and X. Hou, “Shape measurement of objects using an ultrafast optical Kerr gate of Bismuth glass,” J. Appl. Phys.107, 043104 (2010).
[CrossRef]

Tan, W.-J.

J.-Y. Tong, W.-J. Tan, J.-H. Si, F. Chen, W.-H. Yi, and X. Hou, “High Time-resolved imaging of targets in turbid media using ultrafast optical Kerr gate,” Chinese Phys. Lett.29, 024207 (2012).
[CrossRef]

Tankersley, L. L.

Tong, J.

W. Tan, Y. Yang, J. Si, J. Tong, W. Yi, F. Chen, and X. Hou, “Shape measurement of objects using an ultrafast optical Kerr gate of Bismuth glass,” J. Appl. Phys.107, 043104 (2010).
[CrossRef]

Tong, J.-Y.

J.-Y. Tong, W.-J. Tan, J.-H. Si, F. Chen, W.-H. Yi, and X. Hou, “High Time-resolved imaging of targets in turbid media using ultrafast optical Kerr gate,” Chinese Phys. Lett.29, 024207 (2012).
[CrossRef]

Wang, L.

L. Wang, Y. Liu, P. P. Ho, and R. R. Alfano, “Ballistic imaging of biomedical samples using picosecond optical Kerr gate,” Proc. SPIE1431, 97–101 (1991).
[CrossRef]

L. Wang, P. Ho, C. Liu, G. Zhang, and R. Alfano, “Ballistic 2-d imaging through scattering walls using an ultrafast optical Kerr gate,” Science253, 769–771 (1991).
[CrossRef] [PubMed]

Xing, Q.

Xu, Z.

T. Li, H. Feng, Z. Xu, X. Li, Z. Cen, and Q. Li, “Comparison of different analytical edge spread function models for MTF calculation using curve-fitting,” Proc. SPIE7498, 74981H (2009).
[CrossRef]

Yang, Y.

W. Tan, Y. Yang, J. Si, J. Tong, W. Yi, F. Chen, and X. Hou, “Shape measurement of objects using an ultrafast optical Kerr gate of Bismuth glass,” J. Appl. Phys.107, 043104 (2010).
[CrossRef]

Yi, W.

W. Tan, Y. Yang, J. Si, J. Tong, W. Yi, F. Chen, and X. Hou, “Shape measurement of objects using an ultrafast optical Kerr gate of Bismuth glass,” J. Appl. Phys.107, 043104 (2010).
[CrossRef]

Yi, W.-H.

J.-Y. Tong, W.-J. Tan, J.-H. Si, F. Chen, W.-H. Yi, and X. Hou, “High Time-resolved imaging of targets in turbid media using ultrafast optical Kerr gate,” Chinese Phys. Lett.29, 024207 (2012).
[CrossRef]

Yoo, K. M.

Zhang, G.

L. Wang, P. Ho, C. Liu, G. Zhang, and R. Alfano, “Ballistic 2-d imaging through scattering walls using an ultrafast optical Kerr gate,” Science253, 769–771 (1991).
[CrossRef] [PubMed]

Ann. N. Y. Acad. Sci. (1)

R. R. Alfano, S. G. Demos, and S. K. Gayen, “Advances in optical imaging of biomedical media,” Ann. N. Y. Acad. Sci.820, 248–271 (1997).
[CrossRef] [PubMed]

Chinese Phys. Lett. (1)

J.-Y. Tong, W.-J. Tan, J.-H. Si, F. Chen, W.-H. Yi, and X. Hou, “High Time-resolved imaging of targets in turbid media using ultrafast optical Kerr gate,” Chinese Phys. Lett.29, 024207 (2012).
[CrossRef]

Exp. Fluids (1)

S. Idlahcen, C. Rozé, L. Méès, T. Girasole, and J.-B. Blaisot, “Sub-picosecond ballistic imaging of a liquid jet,” Exp. Fluids52, 289–298 (2011).
[CrossRef]

J. Appl. Phys. (2)

D. Newns, B. Elmegreen, X. Hu Liu, and G. Martyna, “A low-voltage high-speed electronic switch based on piezoelectric transduction,” J. Appl. Phys.111, 084509 (2012).
[CrossRef]

W. Tan, Y. Yang, J. Si, J. Tong, W. Yi, F. Chen, and X. Hou, “Shape measurement of objects using an ultrafast optical Kerr gate of Bismuth glass,” J. Appl. Phys.107, 043104 (2010).
[CrossRef]

J. Chem. Phys. (1)

I. A. Heisler, R. R. B. Correia, T. Buckup, S. L. S. Cunha, and N. P. da Silveira, “Time-resolved optical Kerr-effect investigation on CS2/polystyrene mixtures,” J. Chem. Phys.123, 054509 (2005).
[CrossRef] [PubMed]

J. Opt. Soc. Am. A (2)

Opt. Express (2)

Opt. Lett. (2)

Proc. SPIE (2)

T. Li, H. Feng, Z. Xu, X. Li, Z. Cen, and Q. Li, “Comparison of different analytical edge spread function models for MTF calculation using curve-fitting,” Proc. SPIE7498, 74981H (2009).
[CrossRef]

L. Wang, Y. Liu, P. P. Ho, and R. R. Alfano, “Ballistic imaging of biomedical samples using picosecond optical Kerr gate,” Proc. SPIE1431, 97–101 (1991).
[CrossRef]

Prog. Energ. Combust. (1)

M. Linne, “Imaging in the optically dense regions of a spray: A review of developing techniques,” Prog. Energ. Combust.39, 403–440 (2013).
[CrossRef]

Science (1)

L. Wang, P. Ho, C. Liu, G. Zhang, and R. Alfano, “Ballistic 2-d imaging through scattering walls using an ultrafast optical Kerr gate,” Science253, 769–771 (1991).
[CrossRef] [PubMed]

Other (2)

R. Alfano, ed., Semiconductors probed by ultrafast laser spectroscopy (Academic, 1984), Vol. II.

International Standard ISO 12233, Photography - Electronic still-picture cameras - Resolution measurement, ISO, 2000.

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OSA participates in CrossRef's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

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Figures (10)

Fig. 1
Fig. 1

Schematic showing the working principle of crossed-beam OKE based time-gating.

Fig. 2
Fig. 2

Schematic showing the overlap of pump and imaging pulses inside the Kerr medium in a crossed-beam configuration. α: angle between pump and probe beams, p: pump pulse width or duration, q: probe pulse width or duration (extended due to its interaction with the object/sample), Δt: time difference between the two sides of the obtained images.

Fig. 3
Fig. 3

Temporal profiles for the crossed-beam configuration of the optical gate with 1.0 mm of CS2 as Kerr medium for different crossing angles (α) between the pump and the probe beams.

Fig. 4
Fig. 4

Schematic of the experimental set-up for dual wavelength OKE based time-gate with collinear incidence of pump and probe beams at the Kerr medium. BS: 50/50 beamsplitter, (M1, M2, M3, M4): mirrors, (D1, D2): dichroic mirrors, (P1, P2): polarizers, H1: half wave-plate, (F1, F2): neutral density filters, BBO: β -barium borate crystal, (L1, L2): bi-convex lenses with focal lengths 300 mm and 100 mm respectively, F3, F4: filters to block pump (800 nm) and select only probe (400 nm) for detection.

Fig. 5
Fig. 5

Average line profiles of the probe beam after passing through 1.0 mm CS2 optical time-gate for (a) non-collinear and (b) collinear incidence of the pump and probe beams at the Kerr medium for different delays between the two.

Fig. 6
Fig. 6

Temporal profile of the dual wavelength, collinear OKE based time-gate with liquid CS2 as Kerr medium for three different thicknesses of the CS2 cell - 10 mm, 2.0 mm and 1.0 mm. The average power of the pump beam for all these measurements was 0.34 W.

Fig. 7
Fig. 7

(a) Image of a slanted glass fibre (245 μm) obtained using collinear time-gate configuration with 1.0 mm thick CS2 cell and the corresponding averaged edge-spread function (ESF) for the indicated edge in the image. (b) The normalized modulation transfer function (MTF) as a function of spatial frequency (ν) (in lines/mm) calculated using the fitted ESFs for the collinear and crossed-beam configurations of the optical gate. Note that in the collinear configuration the Kerr medium (CS2) was placed at the image plane (IP) of the lens L1 whereas in the crossed-beam configuration it was placed at the Fourier plane (FP) of L1.

Fig. 8
Fig. 8

Ballistic and refraction images of a 342 μm micro-structured optical fibre (LMA-25) obtained using 1.0 mm CS2 optical gate. The hidden microstructures are visible in the refraction image. Average pump power 0.34 W.

Fig. 9
Fig. 9

Ballistic and refraction images of fuel spray close to the injector (Bosch, single orifice ϕ = 185 μm) separated using 1.0 mm CS2 optical time-gate.

Fig. 10
Fig. 10

Schematic to show the ballistic and the refracted light signals through a 185 μm thick medium with the refractive index of 1.46 (black, solid line curve). The blue, solid and dashed curves shows the transmission through the 1.0 mm CS2 optical time-gate (gate duration ∼ 1.0 ps) for two different delay configurations, separating ballistic and refraction light signals.

Equations (3)

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I t I 0 = sin 2 ( Δ ϕ 2 ) sin 2 ( 2 θ )
MTF ( ν ) = d F ( x ) d x e i 2 π ν x d x
F ( x ) = d + f ( x ) = d + a 1 + exp [ ( x b ) / c ]

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