Abstract

The molecular nonlinear photonic absorption processes of two nonlinear fiber core liquids are discussed in the context of nonlinear propagation and optical limiting of short pulses. These fiber arrays are capable of limiting threshold and clamped output below 1 μJ for picosecond and nanosecond pulses. We also discuss the observation of perhaps the largest optical nonlinearity in some dye-doped nematic liquid crystal films. These films will provide limiting action with a threshold power of 100 nWatt and limited transmission of ≪ 1 microJoule for ms - cw laser.

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References

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  1. See, for example, L. Tutt and T. Boggess, Prog. Quantum Electron. 17, 299-338 (1993).
    [CrossRef]
  2. I. C. Khoo, M. V. Wood and Brett D. Guenther, Opt. Lett. 21, 1625-1627 (1996) and references therein.
    [CrossRef] [PubMed]
  3. I. C. Khoo and H. Li, J. Appl. Phys. B59, 573 (1994).
  4. F. W. Deeg and M. D. Feyer, J. Chem. Phys. 91, 2269 (1989)
    [CrossRef]
  5. H. J. Eichler, R. Macdonald and B. Trosken, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A. 231, 1 (1993)
    [CrossRef]
  6. R. J. McEwan and R. C. Hollins, J. Nonlinear Opt. Phys. Mater. 4, 245-260 (1995).
    [CrossRef]
  7. For Fullerene systems, see for example, K. M. Nashold and D. P. Walter, J. Opt. Soc.Am. B. 12, 1228-1237 (1995) and references therein
    [CrossRef]
  8. I. C. Khoo, Liquid Crystals: Physical Properties and Nonlinear Optical Phenomena, (Wiley Interscience, New York, 1994) chap. 2, p. 21 and references therein.
  9. I. C. Khoo, M. V. Wood, B. D.Guenther, Min-Yi Shih and P. H. Chen, J. Opt. Soc. Am. B, 1533-1540, (1998)
  10. I. C. Khoo, S. Slussarenko, B. D. Guenther, Min-Yi Shih, P. Chen and M. V. Wood, Opt. Lett. 23, 253-255 (1998)
    [CrossRef]
  11. I. C. Khoo, J. Y. Hou, T. H. Lui, P. Y. Yan, R. R. Michael and G. M. Finn, J. Opt. Soc. Am. B, 4, 886-891, (1987).
    [CrossRef]

Other (11)

See, for example, L. Tutt and T. Boggess, Prog. Quantum Electron. 17, 299-338 (1993).
[CrossRef]

I. C. Khoo, M. V. Wood and Brett D. Guenther, Opt. Lett. 21, 1625-1627 (1996) and references therein.
[CrossRef] [PubMed]

I. C. Khoo and H. Li, J. Appl. Phys. B59, 573 (1994).

F. W. Deeg and M. D. Feyer, J. Chem. Phys. 91, 2269 (1989)
[CrossRef]

H. J. Eichler, R. Macdonald and B. Trosken, Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A. 231, 1 (1993)
[CrossRef]

R. J. McEwan and R. C. Hollins, J. Nonlinear Opt. Phys. Mater. 4, 245-260 (1995).
[CrossRef]

For Fullerene systems, see for example, K. M. Nashold and D. P. Walter, J. Opt. Soc.Am. B. 12, 1228-1237 (1995) and references therein
[CrossRef]

I. C. Khoo, Liquid Crystals: Physical Properties and Nonlinear Optical Phenomena, (Wiley Interscience, New York, 1994) chap. 2, p. 21 and references therein.

I. C. Khoo, M. V. Wood, B. D.Guenther, Min-Yi Shih and P. H. Chen, J. Opt. Soc. Am. B, 1533-1540, (1998)

I. C. Khoo, S. Slussarenko, B. D. Guenther, Min-Yi Shih, P. Chen and M. V. Wood, Opt. Lett. 23, 253-255 (1998)
[CrossRef]

I. C. Khoo, J. Y. Hou, T. H. Lui, P. Y. Yan, R. R. Michael and G. M. Finn, J. Opt. Soc. Am. B, 4, 886-891, (1987).
[CrossRef]

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Figures (12)

Fig. 1.
Fig. 1.

Optical limiting setup using a nonlinear fiber array.

Fig. 2.
Fig. 2.

Nonlinear optical processes occurring at the entrance region and the fiber core that limit the transmission of a laser pulse through the fiber.

Fig. 3
Fig. 3

Linear absorption spectrum and molecular structure of L34

Fig. 4.
Fig. 4.

Schematic depiction of two-photon, sequential intermediate state, and excited-state absorption processes, intersystem crossing, and other processes occurring in the core molecule.

Fig. 5a.
Fig. 5a.

Output intensity versus input intensity with different values of γ for β2 > 4αγ, α = 2 cm-1, β = 2.5 cm/GW, z = 0.5 cm.

Fig. 5b.
Fig. 5b.

Output intensity versus input intensity with different values of γ for β2 < 4αγ, α = 2 cm-1, β = 2.5 cm/GW, z = 0.5 cm.

Fig. 6.
Fig. 6.

Transmission and transmitted laser pulse energies versus the input picosecond laser pulse energy through fibers. Fiber length = 5 mm. Core diameter=30 μm. F6 optics.

Fig. 7.
Fig. 7.

Output versus input energies for nanosecond laser pulses [λ = 0.532 μm; pulse width = 20 ns]. Fiber length = 5 mm; core diameter = 30 μm, F6 optics

Fig. 8.
Fig. 8.

Output versus input energies for nanosecond laser pulses [λ==0.532 nm; pulse width: 2 ns] for different F# optics. Fiber length: 5 mm; fiber core diameter: 30 μm; core material: C60-doped ILC.

Fig. 9.
Fig. 9.

Measured single nanosecond pulse transmitted versus input laser energy through a nonlinear fiber. Fiber length: 5 mm; fiber core diameter: 30 mm; core material: L34. Solid triangles are for transparent glass cladding [no coating], while open diamonds are for ‘simulated’ opaque cladding [with absorbing coating]. Also shown are results with bulk sample of the same thickness and input laser focal plane location

Fig. 10.
Fig. 10.

Experimental set up for optical limiting action using external self-defocusing effect. The insert is a photograph of the transmitted laser beam at the aperture showing self-defocusing effect.

Fig. 11.
Fig. 11.

Plot of detected output power versus input laser power. Insert is an oscilloscope trace of the detected output for an input step-on cw laser.

Equations (17)

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d N 2 dt = σ ( 2 ) I 2 2 h 2 υ 2 N 1 N 2 τ 21 N 2 τ 2 i N 2 σ exc I + N i σ i I
α g = N 0 σ g ; α exc = N 0 σ exc ; α i = N 0 σ i ; β = N 0 σ ( 2 )
N 1 ~ N 0 e ( B + C ) t ~ N 0 [ 1 ( B + C ) t ]
N 2 ~ [ B B + C N 0 [ 1 e ( B + C ) t ] ] ~ B N 0 t
N i ~ C B + C N 0 [ 1 e ( B + C ) t ] ~ C N 0 t
B = β I 2 N 0 2
C = σ g I = α g I N 0
dI dz = α g N 1 N 0 I α i N i N 0 I β N 1 N 0 I 2 α exc N 2 N 0 I
dI dz = α g I ( α i α g ) ICt β I 2 ( α exc α g ) IBt
dI dz = α g I [ β + ( α i α g ) σ g t I 2 ( α exc α g ) I 3 N 0 2
= α g I β eff I 2 γ I 3
2 αz = [ ln I 2 ( z ) α + βI ( z ) + γ I 2 ( z ) ln I 0 2 α + β I 0 + γ I 0 2 ]
β β 2 4 αγ [ ln 2 γI ( z ) + β β 2 4 αγ 2 γI ( z ) + β + β 2 4 αγ ln 2 γ I 0 + β β 2 4 αγ 2 γ I 0 + β + β 2 4 αγ ]
2 αz = [ ln I 2 ( z ) I 0 2 ( α + βI ( z ) + γ I 2 ( z ) ) ( α + β I 0 + γ I 0 2 ) ]
2 β 4 αγ β 2 [ tan 1 2 γI ( z ) + β 4 αγ β 2 tan 1 2 γ I 0 + β 4 αγ β 2 ]
I ( L ) = αI ( 0 ) α g e αL βI ( 0 ) ( 1 α g e αL )
I clamped = 1 βL

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