Abstract

Fiber lasers of neodymium-doped glass have been used on a pulsed basis to amplify 1.06-μ radiation. To prevent oscillation, the ends are polished at an angle such that reflected light is lost from the cavity. With the high inversion which can then be obtained, gains as large as 5 × 104 have been observed in a 1-m long fiber. The gain was measured as a function of pumping energy and as a function of time during the pumping pulse at which the amplification was determined.

© 1964 Optical Society of America

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References

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  1. P. P. Kisliuk, W. S. Boyle, Proc. Inst. Radio Engrs. 49, 1635 (1961).
  2. J. E. Geusic, H. E. D. Scovil, Bell Syst. Tech. J. 41, 1371 (1962).
  3. S. Jacobs, G. Gould, P. Rabinowitz, Phys. Rev. Letters 7, 415 (1961).
    [CrossRef]
  4. A. L. Bloom, W. E. Bell, R. C. Rempel, Appl. Opt. 2, 317 (1963).
    [CrossRef]
  5. J. D. Rigden, A. D. White, E. I. Gordon, NEREM, Boston, Mass., Nov.6, 1962; Proc. Inst. Radio Engrs. 50, 1697 (1962).
  6. C. K. N. Patel, W. R. Bennett, W. L. Faust, R. A. McFarlane, Phys. Rev. Letters 9, 102 (1962).
    [CrossRef]
  7. R. A. Paananen, Proc. Inst. Radio Engrs. 50, 2115 (1962).
  8. E. Snitzer, C. J. Koester in Optical Processing of Information (Spartan Books, Baltimore, Md., 1963).
  9. E. Snitzer, J. Appl. Phys. 32, 36 (1961); Phys. Rev. Letters 7, 444 (1961).
    [CrossRef]

1963

1962

J. E. Geusic, H. E. D. Scovil, Bell Syst. Tech. J. 41, 1371 (1962).

C. K. N. Patel, W. R. Bennett, W. L. Faust, R. A. McFarlane, Phys. Rev. Letters 9, 102 (1962).
[CrossRef]

R. A. Paananen, Proc. Inst. Radio Engrs. 50, 2115 (1962).

1961

E. Snitzer, J. Appl. Phys. 32, 36 (1961); Phys. Rev. Letters 7, 444 (1961).
[CrossRef]

S. Jacobs, G. Gould, P. Rabinowitz, Phys. Rev. Letters 7, 415 (1961).
[CrossRef]

P. P. Kisliuk, W. S. Boyle, Proc. Inst. Radio Engrs. 49, 1635 (1961).

Bell, W. E.

Bennett, W. R.

C. K. N. Patel, W. R. Bennett, W. L. Faust, R. A. McFarlane, Phys. Rev. Letters 9, 102 (1962).
[CrossRef]

Bloom, A. L.

Boyle, W. S.

P. P. Kisliuk, W. S. Boyle, Proc. Inst. Radio Engrs. 49, 1635 (1961).

Faust, W. L.

C. K. N. Patel, W. R. Bennett, W. L. Faust, R. A. McFarlane, Phys. Rev. Letters 9, 102 (1962).
[CrossRef]

Geusic, J. E.

J. E. Geusic, H. E. D. Scovil, Bell Syst. Tech. J. 41, 1371 (1962).

Gordon, E. I.

J. D. Rigden, A. D. White, E. I. Gordon, NEREM, Boston, Mass., Nov.6, 1962; Proc. Inst. Radio Engrs. 50, 1697 (1962).

Gould, G.

S. Jacobs, G. Gould, P. Rabinowitz, Phys. Rev. Letters 7, 415 (1961).
[CrossRef]

Jacobs, S.

S. Jacobs, G. Gould, P. Rabinowitz, Phys. Rev. Letters 7, 415 (1961).
[CrossRef]

Kisliuk, P. P.

P. P. Kisliuk, W. S. Boyle, Proc. Inst. Radio Engrs. 49, 1635 (1961).

Koester, C. J.

E. Snitzer, C. J. Koester in Optical Processing of Information (Spartan Books, Baltimore, Md., 1963).

McFarlane, R. A.

C. K. N. Patel, W. R. Bennett, W. L. Faust, R. A. McFarlane, Phys. Rev. Letters 9, 102 (1962).
[CrossRef]

Paananen, R. A.

R. A. Paananen, Proc. Inst. Radio Engrs. 50, 2115 (1962).

Patel, C. K. N.

C. K. N. Patel, W. R. Bennett, W. L. Faust, R. A. McFarlane, Phys. Rev. Letters 9, 102 (1962).
[CrossRef]

Rabinowitz, P.

S. Jacobs, G. Gould, P. Rabinowitz, Phys. Rev. Letters 7, 415 (1961).
[CrossRef]

Rempel, R. C.

Rigden, J. D.

J. D. Rigden, A. D. White, E. I. Gordon, NEREM, Boston, Mass., Nov.6, 1962; Proc. Inst. Radio Engrs. 50, 1697 (1962).

Scovil, H. E. D.

J. E. Geusic, H. E. D. Scovil, Bell Syst. Tech. J. 41, 1371 (1962).

Snitzer, E.

E. Snitzer, J. Appl. Phys. 32, 36 (1961); Phys. Rev. Letters 7, 444 (1961).
[CrossRef]

E. Snitzer, C. J. Koester in Optical Processing of Information (Spartan Books, Baltimore, Md., 1963).

White, A. D.

J. D. Rigden, A. D. White, E. I. Gordon, NEREM, Boston, Mass., Nov.6, 1962; Proc. Inst. Radio Engrs. 50, 1697 (1962).

Appl. Opt.

Bell Syst. Tech. J.

J. E. Geusic, H. E. D. Scovil, Bell Syst. Tech. J. 41, 1371 (1962).

J. Appl. Phys.

E. Snitzer, J. Appl. Phys. 32, 36 (1961); Phys. Rev. Letters 7, 444 (1961).
[CrossRef]

Phys. Rev. Letters

S. Jacobs, G. Gould, P. Rabinowitz, Phys. Rev. Letters 7, 415 (1961).
[CrossRef]

C. K. N. Patel, W. R. Bennett, W. L. Faust, R. A. McFarlane, Phys. Rev. Letters 9, 102 (1962).
[CrossRef]

Proc. Inst. Radio Engrs.

R. A. Paananen, Proc. Inst. Radio Engrs. 50, 2115 (1962).

P. P. Kisliuk, W. S. Boyle, Proc. Inst. Radio Engrs. 49, 1635 (1961).

Other

E. Snitzer, C. J. Koester in Optical Processing of Information (Spartan Books, Baltimore, Md., 1963).

J. D. Rigden, A. D. White, E. I. Gordon, NEREM, Boston, Mass., Nov.6, 1962; Proc. Inst. Radio Engrs. 50, 1697 (1962).

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Figures (9)

Fig. 1
Fig. 1

Coiled fiber laser. From the top the components are: cavity, fiber laser, flashtube, and 18 cm scale

Fig. 2
Fig. 2

Experimental setup for measuring amplification. Signal laser: 6.35-mm diam core, 9.5-mm diam cladding, 30.5-cm long. Filters, A, in front of the phototube pass only the 1.06-μ laser radiation. Filters, B, partially absorb at 1.06 to keep the signal within the linear range.

Fig. 3
Fig. 3

Arrangement of end caps on fiber lasers. The iris diaphragm is mounted on the front of the photomultiplier housing, and together with the exit end cap it provides a light trap.

Fig. 4
Fig. 4

Oscilloscope traces showing fiber laser amplification. Time increases to the right, and the signal is negative. Upper trace: fiber laser output as detected by photomultiplier. Lower trace: monitor of laser rod output. Fiber laser pump energy (a) 220 J; (b) 0. Sweep speed, μsec/cm: (a) 5; (b) 2. Oscilloscope vertical sensitivity, v/cm: (a) 0.02; (b) 0.005. Transmittance of filters between rod and fiber: (a) 0.023; (b) 1.0. Transmittance of filters between fiber and PM: (a) 0.00195; (b) 1.0. Calculated gross gain: 85,000. For fiber data, see Fig. 9.

Fig. 5
Fig. 5

Amplification at several pumping levels. Each trace represents the signal out of the fiber laser amplifier. Starting from the top, the pumping levels were 0, 5 J, 10 J, 15 J, 20 J, and 25 J. The input signal and oscilloscope sensitivity were the same in each case. For fiber data, see Fig. 6.

Fig. 6
Fig. 6

Amplification as a function of pumping energy. Fiber data: 25-μ core diameter, 1.5-mm cladding diameter, core glass contained 6.3 wt% Nd2O3 in a barium crown base, core index 1.531, cladding index 1.51. Pumped length 110 cm, total length 119 cm. In the case of 30 J and 35 J pumping, amplification was measured just before the fiber oscillated. The solid curve represents the measured ratio of Ip/Iu. The dashed curve represents the calculated single pass gain G.

Fig. 7
Fig. 7

Method for eliminating end reflection.

Fig. 8
Fig. 8

Limits on bevel angle. In (a) the extreme meridional ray is reflected back on itself. All other meridional rays are, therefore, reflected at angles such that they do not undergo total internal reflection at the core-cladding interface. In (b) the extreme meridional ray is totally internally reflected at the end surface. If the angle θ is made larger than this value, more of the useful rays will be totally reflected and thereby lost for purposes of amplification.

Fig. 9
Fig. 9

Gross amplification, eβlp, in a fiber laser. Length 1 m, core diameter 10 μ, 2.5% Nd3+ in a barium crown glass. Bevel angle, θ = 10°, on one end. Pump power was supplied by a 7.6-cm straight flashtube (GE FT 91/L). For pumping at 370 J it was necessary to use an inductance in series with the power supply. This accounts for the fact that the peak amplification occurs at a later time than for 220-J pump energy.

Equations (13)

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I = I 0 e - α x ( unpumped ) ,
I p = I 0 e ( β - α ) x ( pumped ) .
G = I p / I 0 = e β l p - α l t .
I u / I 0 = e - α l t .
I p / I u = e β l p .
I p / I 0 = e ( β l p - α l t ) = R 1 .
e β l p - α l t = ( R 1 R 2 ) - 1 2 .
G max = ( R 1 R 2 ) - 1 2 .
G ¯ = ( 1 - R ) 2 G 1 - G 2 R 2 .
Δ λ = λ 2 2 n l = 1 3 × 10 - 2 Å ,
N . A . = n 1 sin ϕ max = n 1 2 - n 2 2 .
cos - 1 n 2 n 1 < θ < sin - 1 1 n 1 - cos - 1 n 2 n 1 .
I p I u = G ¯ e - α l t .

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