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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 17, Iss. 24 — Nov. 23, 2009
  • pp: 21891–21896
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Devil’s vortex-lenses

Walter D. Furlan, Fernando Giménez, Arnau Calatayud, and Juan A. Monsoriu  »View Author Affiliations


Optics Express, Vol. 17, Issue 24, pp. 21891-21896 (2009)
http://dx.doi.org/10.1364/OE.17.021891


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Abstract

In this paper we present a new kind of vortex lenses in which the radial phase distribution is characterized by the “devil’s staircase” function. The focusing properties of these fractal DOEs coined Devil’s vortex-lenses are analytically studied and the influence of the topological charge is investigated. It is shown that under monochromatic illumination a vortex devil’s lens give rise a focal volume containing a delimited chain of vortices that are axially distributed according to the self-similarity of the lens.

© 2009 OSA

1. Introduction

Optical vortices extended the capabilities of conventional optical traps because in addition to trap microparticles they are capable to set these particles into rotation due to the orbital angular momentum of light [1

1. F. S. Roux, “Distribution of angular momentum and vortex morphology in optical beams,” Opt. Commun. 242(1–3), 45–55 ( 2004). [CrossRef]

,2

2. G. Gbur and T. D. Visser, “Phase singularities and coherence vortices in linear optical systems,” Opt. Commun. 259(2), 428–435 ( 2006). [CrossRef]

]. Among the several methods that have been proposed for optical vortices generation the most common approach is the spiral phase plate [3

3. N. R. Heckenberg, R. McDuff, C. P. Smith, and A. G. White, “Generation of optical phase singularities by computer-generated holograms,” Opt. Lett. 17(3), 221–223 ( 1992). [CrossRef] [PubMed]

,4

4. W. M. Lee, X. C. Yuan, and W. C. Cheong, “Optical vortex beam shaping by use of highly efficient irregular spiral phase plates for optical micromanipulation,” Opt. Lett. 29(15), 1796–1798 ( 2004). [CrossRef] [PubMed]

] mainly inasmuch as this technique provides a high energy efficiency. Recently, a method for producing a sequence of focused optical vortices along the propagation direction has been proposed by the use of a spiral fractal zone plate [5

5. S. H. Tao, X.-C. Yuan, J. Lin, and R. Burge, “Sequence of focused optical vortices generated by a spiral fractal zone plates,” Appl. Phys. Lett. 89(3), 031105 ( 2006). [CrossRef]

]. Fractal zone plates (FraZPs) are binary zone plates with fractal profile along the square of the radial coordinate [6

6. G. Saavedra, W. D. Furlan, and J. A. Monsoriu, “Fractal zone plates,” Opt. Lett. 28(12), 971–973 ( 2003). [CrossRef] [PubMed]

,7

7. J. A. Monsoriu, G. Saavedra, and W. D. Furlan, “Fractal zone plates with variable lacunarity,” Opt. Express 12(18), 4227–4234 ( 2004), http://www.opticsinfobase.org/abstract.cfm?URI=oe-12-18-4227. [CrossRef] [PubMed]

]. These new optical elements have deserved the attention of several experimental research groups working in diffractive optics [8

8. J. A. Davis, L. Ramirez, J. A. Martín-Romo, T. Alieva, and M. L. Calvo, “Focusing properties of fractal zone plates: experimental implementation with a liquid-crystal display,” Opt. Lett. 29(12), 1321–1323 ( 2004). [CrossRef] [PubMed]

,9

9. H.-T. Dai, X. Wang, and K.-S. Xu, “Focusing properties of fractal zone plates with variable lacunarity: experimental studies based on liquid crystal on silicon,” Chin. Phys. Lett. 22(11), 2851–2854 ( 2005). [CrossRef]

] and, besides of the above mentioned spiral fractal zone plates, they also inspired the invention of other photonic structures such as optical fibers with fractal cross section [10

10. C. Martelli and J. Canning, “Fresnel Fibres with Omnidirectional Zone Cross-sections,” Opt. Express 15(7), 4281–4286 ( 2007), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-15-7-4281. [CrossRef] [PubMed]

] and fractal photon sieves [11

11. F. Giménez, J. A. Monsoriu, W. D. Furlan, and A. Pons, “Fractal photon sieve,” Opt. Express 14(25), 11958–11963 ( 2006), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-14-25-11958. [CrossRef] [PubMed]

].

The new element we propose, which is referred to as Devil’s vortex-lens (DVL), is a phase-only Devil’s lens modulated by an helical phase structure. Our design is able to generate a sequence of focused vortices surrounding the major foci inside a single main fractal focus. It is because of its blazed profile that DVL has an improved diffraction efficiency with respect to the spiral fractal zone. The focusing properties of different DVLs are studied by computing the intensity distribution along the optical axis and the transverse diffraction patterns along the propagation direction.

2. Vortex devil’s lenses design

The design of a Devil’s lens is mathematically based on the Cantor function [12

12. J. A. Monsoriu, W. D. Furlan, G. Saavedra, and F. Giménez, “Devil’s lenses,” Opt. Express 15(21), 13858–13864 ( 2007), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-15-21-13858. [CrossRef] [PubMed]

,13

13. D. R. Chalice, “A characterization of the Cantor function,” Am. Math. Mon. 98(3), 255–258 ( 1991). [CrossRef]

], which is defined in the domain [0,1] as
Fs(x)={12S                if    pS,lxqS,l12Sxqs,lps,l+1qs,l+l2S        if    qS,lxpS,l+1,
(1)
being FS(0) = 0 and FS(1) = 1. In Fig. 1
Fig. 1 Triadic Cantor set for S = 1, S = 2, and S = 3. The structure for S = 0 is the initiator and the one corresponding to S = 1 is the generator. The Cantor function or Devil’s staircase, FS(x), is shown under the corresponding Cantor set for S = 3.
we have represented the triadic Cantor function F3(x). It can be seen that the steps of the devil’s staircase, take the constant values l/23 in the intervals p 3 ,l≤x≤q 3, l (with l = 1, …,7) whereas in between these intervals the function increases linearly.

From a particular Cantor function FS(x) a DL is defined as a circularly symmetric pure-phase DOE whose transmittance is defined by
q(ς)=exp[iΦDL]=exp[2s+1πFS(ς)],
(2)
where
ς=(r/a)2
(3)
is the normalized quadratic radial variable and a is the lens radius. Thus, the phase variation along the radial coordinate is quadratic in each zone of the lens. At the gap regions defined by the Cantor set the phase shift is –l2π, with l = 1, …, 2S–1. The form of a DL is shown in Fig. 2a
Fig. 2 (a) Phase variation as gray levels for a DL (S = 2), and for DVLs with topological charge (b) m = 1, and (c) m = 3.
) in which the gray levels show the continuous phase variation.

A DVL can be simply constructed from a conventional DL by adding to it the azimuthal variation of the phase that characterize a vortex lens i.e.; ΦVL = imθ, where m is a non zero integer called the topological charge and θ is the azimuthal angle. In this way the phase distribution of DVL is given by: ΦDVL = modDL + ΦVL) being ΦDL the phase of the of a DL (see Eq. (2). Figs. 2b) and 2c) show DVLs with m = 1 and m = 3, respectively. Note in the same figure that a Devil’s lens is a DVL with m = 0. In other words: DVLs can be considered as a generalization of the DLs.

3. Focusing properties of a DVL

Let us consider the diffraction pattern provided by a DVL. The transmittance of this lens, t(r,θ), can be expressed as the product of two factors, the first one, associated to a DL which has only a radial dependence and the other one corresponding to a vortex lens with a linear phase dependence on the azimuthal angle, i.e.;

t(r,θ)=p(r)exp[imθ].
(4)

Within the Fresnel approximation the diffracted field at a given point (z,r,θ), where z is the axial distance from the pupil plane, can be characterized by the irradiance and the phase functions which are given respectively by:

I(z,r)=(2πλz)2|0ap(ro)exp(iπλzro2)Jm(2πrorλz)rodro|2;
(5)
Φ(z,r,θ)=m(θ+π2)2πλzπr2λzπ2;
(6)

In Eqs. (5) and (6) λ is the wavelength of the incident monochromatic plane wave. Now, if the pupil transmittance is defined in terms of the normalized variable in Eq. (3), these equations become
I(u,v)=4π2u2|01q(ς)exp(i2πuς)Jm(4πςuv)dς|2,
(7)
Φ(u,v,θ)=m(θ+π2)πa2λ2u2πuv2π2;
(8)
where q(ς) = p(ro) is given by Eq. (2), and u = a 2/2λz and v = r/a are the reduced axial and transverse coordinates, respectively.

By using the above equations we have computed the irradiance provided by the DVLs shown in Fig. 2. The integrals were numerically evaluated using Simpson's rule using a step length 1/500. As expected, the axial response for the DL (Fig. 2a) represented in Fig. 3a
Fig. 3 Normalized irradiance contours computed for the lenses in Fig. 2. (a) m = 0, (b) m = 1, and (c) m = 3.
) exhibits a single major focus at fs = a 2 /2λ3s and a number of subsidiary focal points surrounding it, producing a focal volume with a characteristic fractal profile. Note that, if we change the topological charge, each focus transforms into a vortex and a chain of doughnut shaped foci is generated. Figs. 3(b) and 3(c) shows the focal volume associated to the DVL with m = 1 and m = 3, respectively. We have also computed the diffraction patterns for different topological charges (not shown) and verified that the diameter of the doughnut increases with the topological charge as happens with conventional vortex producing lenses [18

18. G. A. Swartzlander Jr., “Peering into darkness with a vortex spatial filter,” Opt. Lett. 26(8), 497–499 ( 2001). [CrossRef] [PubMed]

, 19

19. K. Crabtree, J. A. Davis, and I. Moreno, “Optical processing with vortex-producing lenses,” Appl. Opt. 43(6), 1360–1367 ( 2004). [CrossRef] [PubMed]

].

For predicting the focusing capabilities of the DVLs, the diffracted wavefield, over the whole transverse plane is of interest mainly because it can reflect the phase variations of the field from plane to plane. Eq. (5) has been used to calculate the evolution of the diffraction patterns for a DVL (S = 2, m = 1) around the main vortex, u = 9 (Fig. 4a
Fig. 4 Transverse field maps (as the product of the irradiance times phase) at (a) u = 9 and (b) u = 9.8 computed for the lens in Fig. 1(b) with m = 1. The animations Fig. 4a.avi (Media 1, 1.62 MB) and Fig. 4b.avi (Media 2, 2.18 MB) show the evolution of the vortices as they propagate along the optical axis.
) and around the first subsidiary vortex, u = 9.8 (Fig. 4b). In both cases the range of the sampling for the axial coordinate is limited to Δu = −10−7. In the animated Fig. 4 each frame represent the form of the transverse field contours as the product of the irradiance times the phase of the wavefront within the range |x/a|<0.15, |y/a|<0.15. The phase variations are in the range [0,2π], while the intensities are normalized to the maximum value at each transverse plane. In this way, the relative intensity at the vortices can be directly compared. These animations show the annular form of the transverse intensity and also the phase rotation with the axial coordinate. Note that due to the form of this representation only the changes in the phase are relevant since the intensity didn’t change with time. The concentric rings are caused by constructive interferences of the different rings of the DVL. These are affected by the vortex as the whole diffraction pattern.

4. Conclusions

Acknowledgments

We acknowledge the financial support from Ministerio de Ciencia y Tecnología, Spain through grants DPI2006-8309 and DPI2008-02953. We also acknowledge the support from Universidad Politécnica de Valencia (PAID-06-08) and from Generalitat Valenciana through the Project PROMETEO2009-077.

References and Links

1.

F. S. Roux, “Distribution of angular momentum and vortex morphology in optical beams,” Opt. Commun. 242(1–3), 45–55 ( 2004). [CrossRef]

2.

G. Gbur and T. D. Visser, “Phase singularities and coherence vortices in linear optical systems,” Opt. Commun. 259(2), 428–435 ( 2006). [CrossRef]

3.

N. R. Heckenberg, R. McDuff, C. P. Smith, and A. G. White, “Generation of optical phase singularities by computer-generated holograms,” Opt. Lett. 17(3), 221–223 ( 1992). [CrossRef] [PubMed]

4.

W. M. Lee, X. C. Yuan, and W. C. Cheong, “Optical vortex beam shaping by use of highly efficient irregular spiral phase plates for optical micromanipulation,” Opt. Lett. 29(15), 1796–1798 ( 2004). [CrossRef] [PubMed]

5.

S. H. Tao, X.-C. Yuan, J. Lin, and R. Burge, “Sequence of focused optical vortices generated by a spiral fractal zone plates,” Appl. Phys. Lett. 89(3), 031105 ( 2006). [CrossRef]

6.

G. Saavedra, W. D. Furlan, and J. A. Monsoriu, “Fractal zone plates,” Opt. Lett. 28(12), 971–973 ( 2003). [CrossRef] [PubMed]

7.

J. A. Monsoriu, G. Saavedra, and W. D. Furlan, “Fractal zone plates with variable lacunarity,” Opt. Express 12(18), 4227–4234 ( 2004), http://www.opticsinfobase.org/abstract.cfm?URI=oe-12-18-4227. [CrossRef] [PubMed]

8.

J. A. Davis, L. Ramirez, J. A. Martín-Romo, T. Alieva, and M. L. Calvo, “Focusing properties of fractal zone plates: experimental implementation with a liquid-crystal display,” Opt. Lett. 29(12), 1321–1323 ( 2004). [CrossRef] [PubMed]

9.

H.-T. Dai, X. Wang, and K.-S. Xu, “Focusing properties of fractal zone plates with variable lacunarity: experimental studies based on liquid crystal on silicon,” Chin. Phys. Lett. 22(11), 2851–2854 ( 2005). [CrossRef]

10.

C. Martelli and J. Canning, “Fresnel Fibres with Omnidirectional Zone Cross-sections,” Opt. Express 15(7), 4281–4286 ( 2007), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-15-7-4281. [CrossRef] [PubMed]

11.

F. Giménez, J. A. Monsoriu, W. D. Furlan, and A. Pons, “Fractal photon sieve,” Opt. Express 14(25), 11958–11963 ( 2006), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-14-25-11958. [CrossRef] [PubMed]

12.

J. A. Monsoriu, W. D. Furlan, G. Saavedra, and F. Giménez, “Devil’s lenses,” Opt. Express 15(21), 13858–13864 ( 2007), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-15-21-13858. [CrossRef] [PubMed]

13.

D. R. Chalice, “A characterization of the Cantor function,” Am. Math. Mon. 98(3), 255–258 ( 1991). [CrossRef]

14.

F. Doveil, A. Macor, and Y. Elskens, “Direct observation of a devil’s staircase in wave-particle interaction,” Chaos 16(3), 033103 ( 2006). [CrossRef] [PubMed]

15.

M. Hupalo, J. Schmalian, and M. C. Tringides, “Devil’s staircase” in Pb/Si(111) ordered phases,” Phys. Rev. Lett. 90(21), 216106 ( 2003). [CrossRef] [PubMed]

16.

Y. F. Chen, T. H. Lu, K. W. Su, and K. F. Huang, “Devil’s staircase in three-dimensional coherent waves localized on Lissajous parametric surfaces,” Phys. Rev. Lett. 96(21), 213902 ( 2006). [CrossRef] [PubMed]

17.

D. Wu, L.-G. Niu, Q.-D. Chen, R. Wang, and H.-B. Sun, “High efficiency multilevel phase-type fractal zone plates,” Opt. Lett. 33(24), 2913–2915 ( 2008). [CrossRef] [PubMed]

18.

G. A. Swartzlander Jr., “Peering into darkness with a vortex spatial filter,” Opt. Lett. 26(8), 497–499 ( 2001). [CrossRef] [PubMed]

19.

K. Crabtree, J. A. Davis, and I. Moreno, “Optical processing with vortex-producing lenses,” Appl. Opt. 43(6), 1360–1367 ( 2004). [CrossRef] [PubMed]

OCIS Codes
(050.1940) Diffraction and gratings : Diffraction
(050.1970) Diffraction and gratings : Diffractive optics

ToC Category:
Diffraction and Gratings

History
Original Manuscript: June 16, 2009
Revised Manuscript: July 31, 2009
Manuscript Accepted: September 3, 2009
Published: November 16, 2009

Citation
Walter D. Furlan, Fernando Giménez, Arnau Calatayud, and Juan A. Monsoriu, "Devil’s vortex-lenses," Opt. Express 17, 21891-21896 (2009)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-17-24-21891


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References

  1. F. S. Roux, “Distribution of angular momentum and vortex morphology in optical beams,” Opt. Commun. 242(1–3), 45–55 (2004). [CrossRef]
  2. G. Gbur and T. D. Visser, “Phase singularities and coherence vortices in linear optical systems,” Opt. Commun. 259(2), 428–435 (2006). [CrossRef]
  3. N. R. Heckenberg, R. McDuff, C. P. Smith, and A. G. White, “Generation of optical phase singularities by computer-generated holograms,” Opt. Lett. 17(3), 221–223 (1992). [CrossRef] [PubMed]
  4. W. M. Lee, X. C. Yuan, and W. C. Cheong, “Optical vortex beam shaping by use of highly efficient irregular spiral phase plates for optical micromanipulation,” Opt. Lett. 29(15), 1796–1798 (2004). [CrossRef] [PubMed]
  5. S. H. Tao, X.-C. Yuan, J. Lin, and R. Burge, “Sequence of focused optical vortices generated by a spiral fractal zone plates,” Appl. Phys. Lett. 89(3), 031105 (2006). [CrossRef]
  6. G. Saavedra, W. D. Furlan, and J. A. Monsoriu, “Fractal zone plates,” Opt. Lett. 28(12), 971–973 (2003). [CrossRef] [PubMed]
  7. J. A. Monsoriu, G. Saavedra, and W. D. Furlan, “Fractal zone plates with variable lacunarity,” Opt. Express 12(18), 4227–4234 (2004), http://www.opticsinfobase.org/abstract.cfm?URI=oe-12-18-4227 . [CrossRef] [PubMed]
  8. J. A. Davis, L. Ramirez, J. A. Martín-Romo, T. Alieva, and M. L. Calvo, “Focusing properties of fractal zone plates: experimental implementation with a liquid-crystal display,” Opt. Lett. 29(12), 1321–1323 (2004). [CrossRef] [PubMed]
  9. H.-T. Dai, X. Wang, and K.-S. Xu, “Focusing properties of fractal zone plates with variable lacunarity: experimental studies based on liquid crystal on silicon,” Chin. Phys. Lett. 22(11), 2851–2854 (2005). [CrossRef]
  10. C. Martelli and J. Canning, “Fresnel Fibres with Omnidirectional Zone Cross-sections,” Opt. Express 15(7), 4281–4286 (2007), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-15-7-4281 . [CrossRef] [PubMed]
  11. F. Giménez, J. A. Monsoriu, W. D. Furlan, and A. Pons, “Fractal photon sieve,” Opt. Express 14(25), 11958–11963 (2006), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-14-25-11958 . [CrossRef] [PubMed]
  12. J. A. Monsoriu, W. D. Furlan, G. Saavedra, and F. Giménez, “Devil’s lenses,” Opt. Express 15(21), 13858–13864 (2007), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-15-21-13858 . [CrossRef] [PubMed]
  13. D. R. Chalice, “A characterization of the Cantor function,” Am. Math. Mon. 98(3), 255–258 (1991). [CrossRef]
  14. F. Doveil, A. Macor, and Y. Elskens, “Direct observation of a devil’s staircase in wave-particle interaction,” Chaos 16(3), 033103 (2006). [CrossRef] [PubMed]
  15. M. Hupalo, J. Schmalian, and M. C. Tringides, “Devil’s staircase” in Pb/Si(111) ordered phases,” Phys. Rev. Lett. 90(21), 216106 (2003). [CrossRef] [PubMed]
  16. Y. F. Chen, T. H. Lu, K. W. Su, and K. F. Huang, “Devil’s staircase in three-dimensional coherent waves localized on Lissajous parametric surfaces,” Phys. Rev. Lett. 96(21), 213902 (2006). [CrossRef] [PubMed]
  17. D. Wu, L.-G. Niu, Q.-D. Chen, R. Wang, and H.-B. Sun, “High efficiency multilevel phase-type fractal zone plates,” Opt. Lett. 33(24), 2913–2915 (2008). [CrossRef] [PubMed]
  18. G. A. Swartzlander., “Peering into darkness with a vortex spatial filter,” Opt. Lett. 26(8), 497–499 (2001). [CrossRef] [PubMed]
  19. K. Crabtree, J. A. Davis, and I. Moreno, “Optical processing with vortex-producing lenses,” Appl. Opt. 43(6), 1360–1367 (2004). [CrossRef] [PubMed]

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