Abstract

A saturable-absorber-based technique for spatial filtering of high-average-power laser beams is described. For a focused, radially symmetric beam having its highest intensity at the center, this saturable absorber behaves like a soft aperture with gradually increasing attenuation toward the beam edges, thus selectively transmitting the low divergence components that are confined close to the central axis of the propagating laser beam. This technique has been successfully used to reduce the divergence of a high-power, high-repetition-rate, tunable, narrowband, pulsed dye laser. Our results demonstrate how a judicious choice of operating parameters allows spatial filtering to be achieved with the introduction of a minimum absorption loss of the laser beam in the saturable absorber. Following a time-dependent analysis of a rate equation model describing the propagation and interaction of the laser beam with the saturable absorber, we have also obtained theoretical estimates for the extent of spatial filtering. Our theoretical estimates have been found to be in good agreement with our experimental observations.

© 2006 Optical Society of America

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    [CrossRef]
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    [CrossRef]
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2002 (1)

1998 (1)

1997 (1)

S. Szatmari, Z. Bakonyi, and P. Simon, "Active spatial filtering of laser beams," Opt. Commun. 134, 199-204 (1997).
[CrossRef]

1996 (2)

1979 (1)

P. R. Hammond, "Self-absorption of molecular fluorescence, the design of equipment for measurement of fluorescence decay, and the decay times of some laser dyes," J. Chem. Phys. 70, 3884-3894 (1979).
[CrossRef]

1977 (1)

1976 (1)

C. E. Max, W. C. Mead, and J. J. Thomson, "Mechanisms of the plasma spatial filter for high-power lasers," Appl. Phys. Lett. 29, 783-785 (1976).
[CrossRef]

1975 (1)

U. Ganiel, A. Hardy, G. Neumann, and D. Treves, "Amplified spontaneous emission and signal amplification in dye laser systems," IEEE J. Quantum Electron. OE-11, 881-892 (1975).
[CrossRef]

1967 (1)

Akkara, J. A.

Aoshima, Y.

Aranda, F. J.

Bakonyi, Z.

S. Szatmari, Z. Bakonyi, and P. Simon, "Active spatial filtering of laser beams," Opt. Commun. 134, 199-204 (1997).
[CrossRef]

Dasgupta, K.

Dickey, F. M.

F. M. Dickey and S. C. Holswade, Laser Beam Shaping Theory and Techniques (Marcel Dekker, 2000).
[CrossRef]

Drexhage, K. H.

K. H. Drexhage, "Structure and properties of laser dyes," in Dye Lasers, F. P. Schafer, ed. (Springer-Verlag, 1977).

Egami, C.

Ganiel, U.

U. Ganiel, A. Hardy, G. Neumann, and D. Treves, "Amplified spontaneous emission and signal amplification in dye laser systems," IEEE J. Quantum Electron. OE-11, 881-892 (1975).
[CrossRef]

Goodman, J. W.

J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill, 1968).

Hammond, P. R.

P. R. Hammond, "Self-absorption of molecular fluorescence, the design of equipment for measurement of fluorescence decay, and the decay times of some laser dyes," J. Chem. Phys. 70, 3884-3894 (1979).
[CrossRef]

Hardy, A.

U. Ganiel, A. Hardy, G. Neumann, and D. Treves, "Amplified spontaneous emission and signal amplification in dye laser systems," IEEE J. Quantum Electron. OE-11, 881-892 (1975).
[CrossRef]

Hercher, M.

Holswade, S. C.

F. M. Dickey and S. C. Holswade, Laser Beam Shaping Theory and Techniques (Marcel Dekker, 2000).
[CrossRef]

Ippen, E. P.

C. V. Shank and E. P. Ippen, "Mode-locking of dye lasers," in Dye Lasers, F. P. Schafer, ed. (Springer-Verlag, 1977).

Joseph, J.

Kato, J.

Kundu, S.

Max, C. E.

C. E. Max, W. C. Mead, and J. J. Thomson, "Mechanisms of the plasma spatial filter for high-power lasers," Appl. Phys. Lett. 29, 783-785 (1976).
[CrossRef]

Mead, W. C.

C. E. Max, W. C. Mead, and J. J. Thomson, "Mechanisms of the plasma spatial filter for high-power lasers," Appl. Phys. Lett. 29, 783-785 (1976).
[CrossRef]

Moncur, N. K.

Morton, K. W.

R. D. Richtmyer and K. W. Morton, Difference Methods for Initial Value Problems, 2nd ed. (InterScience/Wiley, 1967).

Nair, S. K. S.

Nakashima, M.

Neumann, G.

U. Ganiel, A. Hardy, G. Neumann, and D. Treves, "Amplified spontaneous emission and signal amplification in dye laser systems," IEEE J. Quantum Electron. OE-11, 881-892 (1975).
[CrossRef]

Okamoto, N.

Pal, T. B.

Rao, D. V. G. L. N.

Ray, A. K.

Richtmyer, R. D.

R. D. Richtmyer and K. W. Morton, Difference Methods for Initial Value Problems, 2nd ed. (InterScience/Wiley, 1967).

Sasikumar, S.

Schafer, F. P.

F. P. Schafer, "Principles of dye laser operation," in Dye Lasers, F. P. Schafer, ed. (Springer-Verlag, 1977).

Shank, C. V.

C. V. Shank and E. P. Ippen, "Mode-locking of dye lasers," in Dye Lasers, F. P. Schafer, ed. (Springer-Verlag, 1977).

Simon, P.

S. Szatmari, Z. Bakonyi, and P. Simon, "Active spatial filtering of laser beams," Opt. Commun. 134, 199-204 (1997).
[CrossRef]

Sinha, S.

Sugihara, O.

Suzuki, Y.

Szatmari, S.

S. Szatmari, Z. Bakonyi, and P. Simon, "Active spatial filtering of laser beams," Opt. Commun. 134, 199-204 (1997).
[CrossRef]

Tallman, C.

C. Tallman and R. Tennant, "Large-scale, excimer-laser-pumped dye lasers," in High Power Dye Lasers, Vol. 65 of Springer Series in Optical Sciences, F.J.Duarte, ed. (Springer-Verlag, 1991).

Tanaka, H.

Tennant, R.

C. Tallman and R. Tennant, "Large-scale, excimer-laser-pumped dye lasers," in High Power Dye Lasers, Vol. 65 of Springer Series in Optical Sciences, F.J.Duarte, ed. (Springer-Verlag, 1991).

Thomson, J. J.

C. E. Max, W. C. Mead, and J. J. Thomson, "Mechanisms of the plasma spatial filter for high-power lasers," Appl. Phys. Lett. 29, 783-785 (1976).
[CrossRef]

Treves, D.

U. Ganiel, A. Hardy, G. Neumann, and D. Treves, "Amplified spontaneous emission and signal amplification in dye laser systems," IEEE J. Quantum Electron. OE-11, 881-892 (1975).
[CrossRef]

Webb, C. E.

C. E. Webb, "High-power dye lasers pumped by copper vapor lasers," in High Power Dye Lasers, Vol. 65 of Springer Series in Optical Sciences, F. J. Duarte, ed. (Springer-Verlag, 1991).

Yamaguchi, I.

Appl. Opt. (3)

Appl. Phys. Lett. (1)

C. E. Max, W. C. Mead, and J. J. Thomson, "Mechanisms of the plasma spatial filter for high-power lasers," Appl. Phys. Lett. 29, 783-785 (1976).
[CrossRef]

IEEE J. Quantum Electron. (1)

U. Ganiel, A. Hardy, G. Neumann, and D. Treves, "Amplified spontaneous emission and signal amplification in dye laser systems," IEEE J. Quantum Electron. OE-11, 881-892 (1975).
[CrossRef]

J. Chem. Phys. (1)

P. R. Hammond, "Self-absorption of molecular fluorescence, the design of equipment for measurement of fluorescence decay, and the decay times of some laser dyes," J. Chem. Phys. 70, 3884-3894 (1979).
[CrossRef]

J. Opt. Soc. Am. B (1)

Opt. Commun. (1)

S. Szatmari, Z. Bakonyi, and P. Simon, "Active spatial filtering of laser beams," Opt. Commun. 134, 199-204 (1997).
[CrossRef]

Opt. Lett. (2)

Other (9)

C. V. Shank and E. P. Ippen, "Mode-locking of dye lasers," in Dye Lasers, F. P. Schafer, ed. (Springer-Verlag, 1977).

K. H. Drexhage, "Structure and properties of laser dyes," in Dye Lasers, F. P. Schafer, ed. (Springer-Verlag, 1977).

F. M. Dickey and S. C. Holswade, Laser Beam Shaping Theory and Techniques (Marcel Dekker, 2000).
[CrossRef]

J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill, 1968).

R. D. Richtmyer and K. W. Morton, Difference Methods for Initial Value Problems, 2nd ed. (InterScience/Wiley, 1967).

Lambda Chrome Laser Grade Dyes Data Sheets, U. Brackmann, ed., Lambda Physik Gmbh, Germany (1986).

F. P. Schafer, "Principles of dye laser operation," in Dye Lasers, F. P. Schafer, ed. (Springer-Verlag, 1977).

C. Tallman and R. Tennant, "Large-scale, excimer-laser-pumped dye lasers," in High Power Dye Lasers, Vol. 65 of Springer Series in Optical Sciences, F.J.Duarte, ed. (Springer-Verlag, 1991).

C. E. Webb, "High-power dye lasers pumped by copper vapor lasers," in High Power Dye Lasers, Vol. 65 of Springer Series in Optical Sciences, F. J. Duarte, ed. (Springer-Verlag, 1991).

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Figures (9)

Fig. 1
Fig. 1

Schematic diagram showing saturable-absorber-based spatial filtering of a dye laser beam.

Fig. 2
Fig. 2

Absorption spectrum of Kiton-Red (K-R) dye (dashed curve) and typical tuning curve of laser emission (solid curve) from a narrowband Rh-6G dye laser.

Fig. 3
Fig. 3

Measured laser transmittance through a saturable absorber as a function of the peak incident laser intensity for laser wavelengths: 572.5 nm (solid circles) and 564 nm (solid triangles). The solid curve (572.5 nm) and the dotted curve (564 nm) depict the corresponding theoretically calculated dependence.

Fig. 4
Fig. 4

Observed spatial profiles of the dye laser beam with and without spatial filtering. Measured intensity distribution of the input beam taken horizontally through the center of the beam at three different dye laser wavelengths: (a) 572, (b) 582, and (c) 564 nm. The corresponding intensity distribution of spatially filtered output beams are shown for the same wavelengths: (d) 572, (e) 582, and (f) 564 nm.

Fig. 5
Fig. 5

Temporal profile of the laser pulse before (m and p), and after (n and q) spatial filtering for incident laser wavelengths of (a) 572 and (b) 582 nm.

Fig. 6
Fig. 6

Temporal profile of the laser beam (a) before and (b) after spatial filtering at an incident laser wavelength of 564 nm.

Fig. 7
Fig. 7

Theoretically calculated transmittance through the saturable absorber dye versus the incident Rh-6G dye laser intensity for varying concentration values of the saturable absorber: 0.25, 0.5, 1.23, and 2.0 mM, respectively.

Fig. 8
Fig. 8

Theoretically estimated spatial profiles for (a) incident focused laser beam (solid curve) and (b) laser beam transmitted through the saturable absorber (dashed curve), indicating spatial filtering via selective removal of the high-divergence component.

Fig. 9
Fig. 9

Temporal profile of the (a) incident laser pulse (dashed curve) and that of corresponding spatially filtered beam (solid curves) for varying peak intensity values: (b) 11.5, (c) 7.5, (d) 4.0, and (e) 3.0 MW∕cm2.

Equations (7)

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N 1 ( r , z , t ) / t = I ( r , z , t ) σ a ( λ ) [ N 0 ( r , z , t ) ] c / η N 1 ( r , z , t ) / τ K S T N 1 ( r , z , t ) ,
N T ( r , z , t ) / t = K S T N 1 ( r , z , t ) N T ( r , z , t ) / τ T ,
N 0 ( r , z , t ) / t = I ( r , z , t ) σ a ( λ ) [ N 0 ( r , z , t ) ] c / η + N T ( r , z , t ) / τ T + N 1 ( r , z , t ) / τ ,
( c / η ) I ( r , z , t ) / z + I ( r , z , t ) / t = I ( r , z , t ) σ a ( λ ) [ N 0 ( r , z , t ) ] c / η ,
N 1 ( r , z , t ) + N 0 ( r , z , t ) + N T ( r , z , t ) = N .
I ( t ) exp [ a ( t 7 ) 2 ] ,
I ( r ) A [ exp a ( r ) 2 ] + B [ exp b ( r ) 2 ] .

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