Abstract

The description of optical fields in terms of their eigenmodes is an intuitive approach for beam characterization. However, there is a lack of unambiguous, pure experimental methods in contrast to numerical phase-retrieval routines, mainly because of the difficulty to characterize the phase structure properly, e.g. if it contains singularities. This paper presents novel results for the complete modal decomposition of optical fields by using computer-generated holographic filters. The suitability of this method is proven by reconstructing various fields emerging from a weakly multi-mode fiber (V ≈ 5) with arbitrary mode contents. Advantages of this approach are its mathematical uniqueness and its experimental simplicity. The method constitutes a promising technique for real-time beam characterization, even for singular beam profiles.

© 2009 Optical Society of America

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References

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  1. N. Hodgson and H. Weber, Laser Resonators and Beam Propagation (Springer, 2005).
  2. A. E. Siegman, Lasers (University Science Books, 1986).
  3. A. P. Napartovich and D. V. Vysotsky, "Theory of spatial mode competition in a fiber amplifier," Phys. Rev. A 76, 063801 (2007).
    [CrossRef]
  4. R. Schermer and J. Cole, "Improved Bend Loss Formula Verified for Optical Fiber by Simulation and Experiment," IEEE J. Quantum Electron. 43, 899-909 (2007).
    [CrossRef]
  5. H. Yoda, P. Polynkin, and M. Mansuripur, "Beam Quality Factor of Higher Order Modes in a Step-Index Fiber," J. Lightwave Technol. 24, 1350 (2006).
    [CrossRef]
  6. O. Shapira, A. F. Abouraddy, J. D. Joannopoulos, and Y. Fink, "Complete Modal Decomposition for Optical Waveguides," Phys. Rev. Lett. 94, 143902 (2005).
    [CrossRef] [PubMed]
  7. J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill Publishing Company, 1968).
  8. V. A. Soifer and M. Golub, Laser Beam Mode Selection by Computer Generated Holograms (CRC Press, 1994).
  9. M. R. Duparre, V. S. Pavelyev, B. Luedge, E.-B. Kley, V. A. Soifer, and R. M. Kowarschik, "Generation, superposition, and separation of Gauss-Hermite modes by means of DOEs," in Diffractive and Holographic Device Technologies and Applications V, I. Cindrich and S. H. Lee, eds., Proc. SPIE 3291, 104-114 (1998).
    [CrossRef]
  10. M. Duparre, B. Ludge and S. Schroter, "On-line characterization of Nd:YAG laser beams by means of modal decomposition using diffractive optical correlation filters," Proc. SPIE 5962, 59622G (2005).
    [CrossRef]
  11. T. Kaiser, B. Ludge, S. Schroter, D. Kauffmann, and M. Duparre, "Detection of mode conversion effects in passive LMA fibres by means of optical correlation analysis," Proc. SPIE 6998, 69980J (2008).
    [CrossRef]
  12. S. J. van Enk and G. Nienhuis, "Photons in polychromatic rotating modes," Phys. Rev. A 76, 053825 (2007).
    [CrossRef]
  13. A. Yariv, Optical Electronics in Modern Communications (Oxford University Press, 1997).
  14. W. H. Lee, "Sampled Fourier Transform Hologram Generated by Computer," Appl. Opt. 9, 639-643 (1970).
    [CrossRef] [PubMed]
  15. T. Kaiser, S. Schroter, and M. Duparre, "Modal decomposition in step-index fibers by optical correlation analysis," in Laser Resonators and Beam Control XI, A. V. Kudryashov, A. H. Paxton, V. S. Ilchenko, and L. Aschke, eds., Proc. SPIE 7194, 719407 (2009).
    [CrossRef]
  16. O. A. Schmidt, T. Kaiser, B. Ludge, S. Schroter, and M. Duparre, "Laser-beam characterization by means of modal decomposition versus M2 method," Proc. SPIE 7194, 71940C (2009).
    [CrossRef]

2007

A. P. Napartovich and D. V. Vysotsky, "Theory of spatial mode competition in a fiber amplifier," Phys. Rev. A 76, 063801 (2007).
[CrossRef]

R. Schermer and J. Cole, "Improved Bend Loss Formula Verified for Optical Fiber by Simulation and Experiment," IEEE J. Quantum Electron. 43, 899-909 (2007).
[CrossRef]

S. J. van Enk and G. Nienhuis, "Photons in polychromatic rotating modes," Phys. Rev. A 76, 053825 (2007).
[CrossRef]

2006

2005

O. Shapira, A. F. Abouraddy, J. D. Joannopoulos, and Y. Fink, "Complete Modal Decomposition for Optical Waveguides," Phys. Rev. Lett. 94, 143902 (2005).
[CrossRef] [PubMed]

1970

Abouraddy, A. F.

O. Shapira, A. F. Abouraddy, J. D. Joannopoulos, and Y. Fink, "Complete Modal Decomposition for Optical Waveguides," Phys. Rev. Lett. 94, 143902 (2005).
[CrossRef] [PubMed]

Cole, J.

R. Schermer and J. Cole, "Improved Bend Loss Formula Verified for Optical Fiber by Simulation and Experiment," IEEE J. Quantum Electron. 43, 899-909 (2007).
[CrossRef]

Fink, Y.

O. Shapira, A. F. Abouraddy, J. D. Joannopoulos, and Y. Fink, "Complete Modal Decomposition for Optical Waveguides," Phys. Rev. Lett. 94, 143902 (2005).
[CrossRef] [PubMed]

Joannopoulos, J. D.

O. Shapira, A. F. Abouraddy, J. D. Joannopoulos, and Y. Fink, "Complete Modal Decomposition for Optical Waveguides," Phys. Rev. Lett. 94, 143902 (2005).
[CrossRef] [PubMed]

Lee, W. H.

Mansuripur, M.

Napartovich, A. P.

A. P. Napartovich and D. V. Vysotsky, "Theory of spatial mode competition in a fiber amplifier," Phys. Rev. A 76, 063801 (2007).
[CrossRef]

Nienhuis, G.

S. J. van Enk and G. Nienhuis, "Photons in polychromatic rotating modes," Phys. Rev. A 76, 053825 (2007).
[CrossRef]

Polynkin, P.

Schermer, R.

R. Schermer and J. Cole, "Improved Bend Loss Formula Verified for Optical Fiber by Simulation and Experiment," IEEE J. Quantum Electron. 43, 899-909 (2007).
[CrossRef]

Shapira, O.

O. Shapira, A. F. Abouraddy, J. D. Joannopoulos, and Y. Fink, "Complete Modal Decomposition for Optical Waveguides," Phys. Rev. Lett. 94, 143902 (2005).
[CrossRef] [PubMed]

van Enk, S. J.

S. J. van Enk and G. Nienhuis, "Photons in polychromatic rotating modes," Phys. Rev. A 76, 053825 (2007).
[CrossRef]

Vysotsky, D. V.

A. P. Napartovich and D. V. Vysotsky, "Theory of spatial mode competition in a fiber amplifier," Phys. Rev. A 76, 063801 (2007).
[CrossRef]

Yoda, H.

Appl. Opt.

IEEE J. Quantum Electron.

R. Schermer and J. Cole, "Improved Bend Loss Formula Verified for Optical Fiber by Simulation and Experiment," IEEE J. Quantum Electron. 43, 899-909 (2007).
[CrossRef]

J. Lightwave Technol.

Phys. Rev. A

A. P. Napartovich and D. V. Vysotsky, "Theory of spatial mode competition in a fiber amplifier," Phys. Rev. A 76, 063801 (2007).
[CrossRef]

S. J. van Enk and G. Nienhuis, "Photons in polychromatic rotating modes," Phys. Rev. A 76, 053825 (2007).
[CrossRef]

Phys. Rev. Lett.

O. Shapira, A. F. Abouraddy, J. D. Joannopoulos, and Y. Fink, "Complete Modal Decomposition for Optical Waveguides," Phys. Rev. Lett. 94, 143902 (2005).
[CrossRef] [PubMed]

Other

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

V. A. Soifer and M. Golub, Laser Beam Mode Selection by Computer Generated Holograms (CRC Press, 1994).

M. R. Duparre, V. S. Pavelyev, B. Luedge, E.-B. Kley, V. A. Soifer, and R. M. Kowarschik, "Generation, superposition, and separation of Gauss-Hermite modes by means of DOEs," in Diffractive and Holographic Device Technologies and Applications V, I. Cindrich and S. H. Lee, eds., Proc. SPIE 3291, 104-114 (1998).
[CrossRef]

M. Duparre, B. Ludge and S. Schroter, "On-line characterization of Nd:YAG laser beams by means of modal decomposition using diffractive optical correlation filters," Proc. SPIE 5962, 59622G (2005).
[CrossRef]

T. Kaiser, B. Ludge, S. Schroter, D. Kauffmann, and M. Duparre, "Detection of mode conversion effects in passive LMA fibres by means of optical correlation analysis," Proc. SPIE 6998, 69980J (2008).
[CrossRef]

A. Yariv, Optical Electronics in Modern Communications (Oxford University Press, 1997).

N. Hodgson and H. Weber, Laser Resonators and Beam Propagation (Springer, 2005).

A. E. Siegman, Lasers (University Science Books, 1986).

T. Kaiser, S. Schroter, and M. Duparre, "Modal decomposition in step-index fibers by optical correlation analysis," in Laser Resonators and Beam Control XI, A. V. Kudryashov, A. H. Paxton, V. S. Ilchenko, and L. Aschke, eds., Proc. SPIE 7194, 719407 (2009).
[CrossRef]

O. A. Schmidt, T. Kaiser, B. Ludge, S. Schroter, and M. Duparre, "Laser-beam characterization by means of modal decomposition versus M2 method," Proc. SPIE 7194, 71940C (2009).
[CrossRef]

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Figures (5)

Fig. 1.
Fig. 1.

Experimental setup for MODAN experiments. The setup is divided into an analytic branch containing the MODAN and a verification branch to check the results. MO1, MO2 - microscope objectives. L1, L2 - imaging lenses. FL - Fourier lens. The combination of MO2 and L1 causes a magnification of the near-field.

Fig. 2.
Fig. 2.

Working principle of optical correlation analysis. The beam emerging the fiber (d) can equivalently be described by the measured correlation pattern (a) which is processed by our software (b) to obtain a reconstructed field (c).

Fig. 3.
Fig. 3.

Modal decomposition of a beam with large amount of higher-order mode content. (a) – near-field of the investigated beam. (b) – reconstruction result. (c) modal excitation statistics for the field.

Fig. 4.
Fig. 4.

Phase resolving character of the MODAN method. (a) – investigated beam. (b) – result of the reconstruction shown with isophase lines. A first order singularity occurs. (c) – 3D-representation of the reconstructed vortex phase front.

Fig. 5.
Fig. 5.

Although the investigated field in (a) seems to be nearly perfect the fundamental mode, the excitation statistics (c) shows that ≈ 15% of the total power is propagating in higher-order modes and leads to a loss in beam quality [5].

Tables (1)

Tables Icon

Table 1. Most important properties of the test fiber used for verification of the MODAN method.

Equations (32)

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(Δ+k2)={E(r)H(r)}=0.
[Δ+k02n2(u)β2]U(u)=0,
U(u,z)=U(u)exp(iβz).
U(u)=n=1nmaxcnψn(u),
ψn,ψm=ψ∫∫2d2uψn*(u)ψm(u)=δnm.
cn=ρnexp(iϕn)=ψn,U=∫∫2d2uψn*(u)U(u),
cn2=ρn2=1.
ψ(u)=R(r)Φ(φ),
R(r)=C·{Jl(Ur/a)Jl(U)raKl(Wr/a)Kl(W)r>a,andΦ(φ)={cos()forevenmodessin()foroddmodes,
UJn+1(U)Jn(U)=WKn+1(W)Kn(W) and U2+W2=V2 ,
U=ak02ncore2β2
W=aβ2k02nclad2,
T(u)=ψn*(u),
U(u)=nnmaxcnψn(u),
W0(u)=ψn*(u)U(u).
Wf(u)=k02πif exp(2ik0f)∫∫2d2uW0(u)exp[ik0fuu]
=2πik0fexp(2ik0f)≗A0 W˜0 (k0fu) ,
𝓕={f(x)g(x)}=[f˜*g˜](k)
Wf(u)=A0 ∫∫2 d2 u ψ˜n* (k0fu)U˜ (k0f[uu]) .
Wf(0)=A0 ψn,U cn .
T(u)=nnmaxψn*(u)exp(iVnu),
W0(u)=nψn*(u)U(u)exp(iVnu),
𝓕{f(x)exp(iv0x)}=f˜(kv0),
Wf(u)=A0n[∫∫2d2uψ˜n*(k0fu)U˜(k0f[uu])Vn],
Wf(un=Vnfk0)2 =A02ψn,W(u)2cn2=ρn2,
Tncos(u)=12 [ψ0*(u)+ψn*(u)]exp(iVncosu)
Tnsin(u)=12 [ψ0*(u)+n*(u)]exp(iVnsinu),
Wf(un=Vncosfk0)2=12 A0(c0+cn)2
=12A02[ρ02+ρn2+2ρ0ρncos(ϕnϕ0)],
Wf(un=Vnsinfk0)2=12 A0(c0+icn)2
=12A02[ρ02+ρn2+2ρ0ρnsin(ϕnϕ0)].
Tnadj(u)=exp(iVnadju) .

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