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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 21, Iss. 4 — Feb. 25, 2013
  • pp: 4005–4016
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Study on power coupling of annular vortex beam propagating through a two-Cassegrain-telescope optical system in turbulent atmosphere

Huiyun Wu, Shen Sheng, Zhisong Huang, Siqing Zhao, Hua Wang, Zhenhai Sun, and Xiegu Xu  »View Author Affiliations


Optics Express, Vol. 21, Issue 4, pp. 4005-4016 (2013)
http://dx.doi.org/10.1364/OE.21.004005


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Abstract

As a new attractive application of the vortex beams, power coupling of annular vortex beam propagating through a two- Cassegrain-telescope optical system in turbulent atmosphere has been investigated. A typical model of annular vortex beam propagating through a two-Cassegrain-telescope optical system is established, the general analytical expression of vortex beams with limited apertures and the analytical formulas for the average intensity distribution at the receiver plane are derived. Under the H-V 5/7 turbulence model, the average intensity distribution at the receiver plane and power coupling efficiency of the optical system are numerically calculated, and the influences of the optical topological charge, the laser wavelength, the propagation path and the receiver apertures on the power coupling efficiency are analyzed. These studies reveal that the average intensity distribution at the receiver plane presents a central dark hollow profile, which is suitable for power coupling by the Cassegrain telescope receiver. In the optical system with optimized parameters, power coupling efficiency can keep in high values with the increase of the propagation distance. Under the atmospheric turbulent conditions, great advantages of vortex beam in power coupling of the two-Cassegrain-telescope optical system are shown in comparison with beam without vortex.

© 2013 OSA

1. Introduction

In recent years, optical beams carrying phase singularities which are known as the vortex beams, have become a live area of scientific research due to their importance in basic science and some attractive applications including microlithography, optical trapping, atom detection and optical communications [1

A. Ambrosio, L. Marrucci, F. Borbone, A. Roviello, and P. Maddalena, “Light-induced spiral mass transport in azo-polymer films under vortex-beam illumination,” Nat Commun 3, 989–991 (2012). [CrossRef] [PubMed]

5

G. Gallatin and B. McMorran, “Propagation of vortex electron wave functions in a magnetic field,” Phys. Rev. A 86(1), 012701 (2012). [CrossRef]

]. The basic characteristics and the turbulent propagation properties of the vortex beams have been widely investigated [5

G. Gallatin and B. McMorran, “Propagation of vortex electron wave functions in a magnetic field,” Phys. Rev. A 86(1), 012701 (2012). [CrossRef]

9

H. T. Dai, Y. J. Liu, D. Luo, and X. W. Sun, “Propagation properties of an optical vortex carried by an Airy beam: experimental implementation,” Opt. Lett. 36(9), 1617–1619 (2011). [CrossRef] [PubMed]

]. Meanwhile, power coupling of optical system with the Cassegrain-telescope receiver has attracted much attention [10

X. Chu and G. Zhou, “Power coupling of a two-Cassegrain-telescopes system in turbulent atmosphere in a slant path,” Opt. Express 15(12), 7697–7707 (2007). [CrossRef] [PubMed]

14

H. Wu, Z. Sun, and J. Chen, “Improving performances of the optical systems with Cassegrain-telescope receivers by using vortex sources and phase optimizations,” Opt. Laser Technol. 45, 132–136 (2013). [CrossRef]

]. Previous researches showed that in the optical system, optical intensity gathers on the center and spreads out on the way up due to the influences of diffraction and the turbulence, when using a Cassegrain-telescope receiver, a large number of optical power losses due to the secondary mirror obstruction and the main mirror truncation [10

X. Chu and G. Zhou, “Power coupling of a two-Cassegrain-telescopes system in turbulent atmosphere in a slant path,” Opt. Express 15(12), 7697–7707 (2007). [CrossRef] [PubMed]

,11

H. Wu, W. Wu, X. Xu, J. Chen, and Y. Zhao, “A new method to improve power efficiencies of optical systems with Cassegrain-telescope receivers,” Opt. Commun. 284(13), 3361–3364 (2011). [CrossRef]

]. The power losses can seriously degrade performance of the optical system, for example, the aerospace relay mirror system (ARMS) used in the outfield experiment at Kirtland Air Force Base N.M in 2006 employed a two-Cassegrain-telescope configuration, and the experimental results showed that power coupling efficiency of the ARMS was merely 50% [12

G. Ren, “Current situation and development trend of high energy laser weapon,” Laser Optoelectronics Prog. 45(9), 62–69 (2008). [CrossRef]

,13

J. Simpson, “Tactical laser relay mirror demonstration anticipated before 2011,” Inside the Air Force 18, 3-7 (2007).

]. How to reduce the serious power losses in optical system with the Cassegrain-telescope receiver has become an urgent work in the scientific research with great importance. Our recent research suggested that under the ideal adaptive optics conditions or the vacuum condition, vortex beams have great advantages in improving power coupling efficiency of optical system with the Cassegrain-telescope receiver [11

H. Wu, W. Wu, X. Xu, J. Chen, and Y. Zhao, “A new method to improve power efficiencies of optical systems with Cassegrain-telescope receivers,” Opt. Commun. 284(13), 3361–3364 (2011). [CrossRef]

,14

H. Wu, Z. Sun, and J. Chen, “Improving performances of the optical systems with Cassegrain-telescope receivers by using vortex sources and phase optimizations,” Opt. Laser Technol. 45, 132–136 (2013). [CrossRef]

]. Namely, power coupling in optical system with Cassegrain-telescope receiver may become a new attractive potential application of the vortex beams [11

H. Wu, W. Wu, X. Xu, J. Chen, and Y. Zhao, “A new method to improve power efficiencies of optical systems with Cassegrain-telescope receivers,” Opt. Commun. 284(13), 3361–3364 (2011). [CrossRef]

,14

H. Wu, Z. Sun, and J. Chen, “Improving performances of the optical systems with Cassegrain-telescope receivers by using vortex sources and phase optimizations,” Opt. Laser Technol. 45, 132–136 (2013). [CrossRef]

]. As a new area of scientific research, power coupling of vortex beam propagating through optical system with the Cassegrain-telescope receiver requires much practical investigation. In actuality, the adaptive optics installations in the optical systems can’t approach the ideal conditions, beams with dark hollow intensity spatial profiles are commonly used as the source and the propagation of laser beam is in a slant path through the turbulent atmosphere [10

X. Chu and G. Zhou, “Power coupling of a two-Cassegrain-telescopes system in turbulent atmosphere in a slant path,” Opt. Express 15(12), 7697–7707 (2007). [CrossRef] [PubMed]

,15

H. Ma, Z. Liu, H. Wu, X. Xu, and J. Chen, “Adaptive correction of vortex laser beam in a closed-loop system with phase only liquid crystal spatial light modulator,” Opt. Commun. 285(6), 859–863 (2012). [CrossRef]

]. To the best of our knowledge, study on the characteristics of power coupling of annular vortex beam propagating through a two-Cassegrain-telescope optical system in turbulent atmosphere has never been reported.

This paper is organized as follows. First, a typical model of annular vortex beam propagating through a two-Cassegrain-telescope optical system in turbulent atmosphere is established, and the analytical formulas for the average intensity distribution at the receiver plane are derived in Section 2. After that, numerical calculations and results analysis are provided in Section 3. In the end, the conclusions are outlined in section 4.

2. Models and theoretical analysis

A typical model of annular vortex beam propagating through a two-Cassegrain-telescope optical system in turbulent atmosphere is shown in Fig. 1 . An annular vortex beam with phase singularity is used as the source, a Cassegrain telescope with central obscuration at the source plane is used as the beam transmitter, and another Cassegrain telescope is used as the beam receiver. The vortex beam propagates from the transmitter to the receiver through the atmospheric turbulence, and the uplink beam is received by the Cassegrain receiver.

Fig. 1 A typical model of annular vortex beam propagating through a two-Cassegrain-telescope optical system in turbulent atmosphere.

The optical field at the source plane can be expressed as
E0(r,θ,0)=E(r,θ,0)t(r,a,b),
(1)
E(r,θ,0)=A(r)exp ( ilθ),
(2)
t(r,a,b)= { 1 arb 0 else,
(3)
where denote the polar coordinates at the source plane, denotes the optical field at the source plane, denotes the optical field of the vortex source, denotes the amplitude, denotes the optical topological charge, denotes the truncation function of the transmitter, denotes the inner radius and denotes the outer radius. In order to reduce power losses induced by the transmitter telescope, dark hollow vortex beams are used. The optical field of a dark hollow vortex beam can be expressed as
E(r,θ,0)= n=1N (1) n1N ( N n) [ exp ( n r2 ω02)exp ( n r2 σ ω02)]exp ( ilθ),
(4)
where Nis the expansion order, n is the offset of the corresponding Gaussian component, ( N n)represents the binomial coefficient, ω0 is the Gaussian waist width, σ ( 0<σ<1) is a parameter concerning the circular dark hollow beam. When N=1 and σ0, Eq. (4) represents a Gaussian vortex beam, and with N increases, Eq. (4) converts to a flattened vortex beam. The area of the dark region across a dark hollow vortex beam increases as σor Nincreases [10

X. Chu and G. Zhou, “Power coupling of a two-Cassegrain-telescopes system in turbulent atmosphere in a slant path,” Opt. Express 15(12), 7697–7707 (2007). [CrossRef] [PubMed]

,16

Z. Mei, D. Zhao, and J. Gu, “Comparison of two approximate methods for hard-edged diffracted flat-topped light beams,” Opt. Commun. 267(1), 58–64 (2006). [CrossRef]

]. By using the Gaussian functions, the truncation function of the transmitter can be expressed as [16

Z. Mei, D. Zhao, and J. Gu, “Comparison of two approximate methods for hard-edged diffracted flat-topped light beams,” Opt. Commun. 267(1), 58–64 (2006). [CrossRef]

,17

H. Mao and D. Zhao, “Different models for a hard-aperture function and corresponding approximate analytical propagation equation of a Gaussian beam through an apertured optical system,” J. Opt. Soc. Am. A 22(4), 647–653 (2005). [CrossRef]

]
t(r,a,b)= w=1M Bw [ exp ( Cw b2 r2)exp ( Cw a2 r2)],
(5)
where Mis the expansion order, Bwand Cw are the complex expansion coefficients. Thus, optical field at the source plane can be expressed as
E0(r,θ,0)= n=1N w=1M (1) n1 BwN ( N n) [ exp ( Cw b2 r2)exp ( Cw a2 r2)] × [ exp ( n r2 ω02)exp ( n r2 σ ω02)]exp ( ilθ).
(6)
Equation (6) represents the general analytical expression of vortex beams with limited apertures. By choosing different l, we can get different optical topological charges; by choosing different ω0 , σand N, we can get different intensity spatial profiles; by choosing different aand b, we can get different aperture functions.

By using the extended Huygens-Fresnel principle, the average intensity distribution at the receiver plane can be expressed as
<I(R,φ,L)>= k2 (2πL)2 0 0 0 2π 0 2π E0( r1, θ1,0)exp { ik 2L [ R2+ r122R r1cos(φ θ1)]} × { E0( r2, θ2,0)exp { ik 2L [ R2+ r222R r2cos(φ θ2)]}} ×<exp [ ψ(R,φ, r1, θ1)+ ψ(R,φ, r2, θ2)]> r1 r2d r1d r2d θ1d θ2,
(7)
where L denotes the propagation distance, (R,φ,L)denote the polar coordinates at the receiver plane, k is the wave number, the asterisk denotes the complex conjugation, the < > indicates the ensemble average over the medium statistics covering the log-amplitude and phase fluctuations due to the turbulent atmosphere, ψ(R,φ,r,θ) represents the random part of the complex phase of a spherical wave that propagates from point (r,θ,0) at the source plane to point (R,φ,L) at the receiver plane. The ensemble average term in Eq. (7) can be expressed as [18

G. Zhou, Y. Cai, and X. Chu, “Propagation of a partially coherent hollow vortex Gaussian beam through a paraxial ABCD optical system in turbulent atmosphere,” Opt. Express 20(9), 9897–9910 (2012). [CrossRef] [PubMed]

,19

H. T. Eyyuboglu, C. Arpali, and Y. K. Baykal, “Flat topped beams and their characteristics in turbulent media,” Opt. Express 14(10), 4196–4207 (2006). [CrossRef] [PubMed]

]
<exp [ ψ(R,φ, r1, θ1)+ ψ(R,φ, r2, θ2)]>=exp [ 0.5 Dψ( r1, r2, θ1, θ2)] =exp { 1 ρ02 [ r12+ r222 r1 r2cos( θ1 θ2)]},
(8)
where Dψ is the wave structure function, ρ0= ( 0.545 Cn2¯ k2L) 3/5 is the coherent length of spherical wave propagating in the turbulence, C¯n2= 1H 0H Cn2(h)dh is the average value of the atmospheric refractive index structure constant along the propagation path, H=Lcosξ is the vertical distance of the propagation path, ξ is the zenith angle, Cn2(h) is the atmospheric refractive index structure constant along the vertical path, h is the altitude from the ground.

Inserting Eq. (6) and Eq. (8) into Eq. (7), the average intensity distribution at the receiver plane can be expressed as
<I(R,φ,L)>= k2 (2πL)2 n=1N m=1N w=1M v=1M (1) n+m N2 ( N n) ( N m) Bw Bv 0 0 0 2π 0 2π exp ( n r12 ω02)exp ( m r22 ω02) ×exp ( Cw a2 r12)exp ( Cv a2 r22)exp { ik 2L [ r122R r1cos(φ θ1) r22+2R r2cos(φ θ2)]} ×exp [ il ( θ1 θ2)]exp { 1 ρ02 [ r122 r1 r2cos( θ1 θ2)+ r22]} r1 r2d r1d r2d θ1d θ2.
(9)
By using the following integral formulas [18

G. Zhou, Y. Cai, and X. Chu, “Propagation of a partially coherent hollow vortex Gaussian beam through a paraxial ABCD optical system in turbulent atmosphere,” Opt. Express 20(9), 9897–9910 (2012). [CrossRef] [PubMed]

21

X. Liu and J. Pu, “Investigation on the scintillation reduction of elliptical vortex beams propagating in atmospheric turbulence,” Opt. Express 19(27), 26444–26450 (2011). [CrossRef] [PubMed]

]
exp [ ikRrαcos(φθ)]= l= il Jl ( kRrα)exp [ il ( φθ)],
(10)
0 2π exp [ ilθ+2αRrcos(θφ)]dθ=2πexp ( ilφ) Il ( 2αRr),
(11)
Il (x)= m=0 ( x/2) 2m+l m!Γ(m+l),
(12)
Jl(x)= ( i)l 2π 0 2π exp ( ixcosθ+ilθ)dθ,
(13)
0 t m1exp ( α t2) Jl(βt)dt= α m/2 2l! ( β2 4α) l/2exp ( β2 4α)Γ ( l+m2) F1 ( m+l+22;l+1; β2 4α),
(14)
and perform the related integrals in Eq. (9). We get that the average intensity distribution at the receiver plane is independent of φand can be expressed as
<I(R,L) >= k2 (2πL)2 n=1N m=1N w=1M v=1M (1) n+m N2 ( N n) ( N m) Bw Bv [ ( T1 T2+ T3 T4) ( T1 T2+ T3 T4)],
(15)
T1= s= t=0 [ Γ( P1)]2 γ 2t+s+l ( s!)2t!Γ ( s+t+l) ( k2 R2 4 L2)s [ exp ( k2 R2 4 H 1,1 L2) F1 ( P2;s+1; k2 R2 4 H 1,1 L2) ( H 1,1) P1]× [ exp ( k2 R2 4 H 1,1 L2) F1 ( P2;s+1; k2 R2 4 H 1,1 L2) ( H 1,1) P1+exp ( k2 R2 4 H 2,2 L2) F1 ( P2;s+1; k2 R2 4 H 2,2 L2) ( H 2,2) P1],
(16)
T2= s= t=0 [ Γ( P1)]2 γ 2t+s+l ( s!)2t!Γ ( s+t+l) ( k2 R2 4 L2)s [ exp ( k2 R2 4 H 1,1 L2) F1 ( P2;s+1; k2 R2 4 H 1,1 L2) ( H 1,1) P1]× [ exp ( k2 R2 4 H 1,2 L2) F1 ( P2;s+1; k2 R2 4 H 1,2 L2) ( H 1,2) P1+exp ( k2 R2 4 H 2,1 L2) F1 ( P2;s+1; k2 R2 4 H 2,1 L2) ( H 2,1) P1],
(17)
T3= s= t=0 [ Γ( P1)]2 γ 2t+s+l ( s!)2t!Γ ( s+t+l) ( k2 R2 4 L2)s [ exp ( k2 R2 4 H 1,2 L2) F1 ( P2;s+1; k2 R2 4 H 1,2 L2) ( H 1,2) P1]× [ exp ( k2 R2 4 H 1,2 L2) F1 ( P2;s+1; k2 R2 4 H 1,2 L2) ( H 1,2) P1+exp ( k2 R2 4 H 2,1 L2) F1 ( P2;s+1; k2 R2 4 H 2,1 L2) ( H 2,1) P1],
(18)
T4= s= t=0 [ Γ( P1)]2 γ 2t+s+l ( s!)2t!Γ ( s+t+l) ( k2 R2 4 L2)s [ exp ( k2 R2 4 H 1,2 L2) F1 ( P2;s+1; k2 R2 4 H 1,2 L2) ( H 1,2) P1]× [ exp ( k2 R2 4 H 1,1 L2) F1 ( P2;s+1; k2 R2 4 H 1,1 L2) ( H 1,1) P1+exp ( k2 R2 4 H 2,2 L2) F1 ( P2;s+1; k2 R2 4 H 2,2 L2) ( H 2,2) P1],
(19)
T1= s= t=0 [ Γ( P1)]2 γ 2t+s+l ( s!)2t!Γ ( s+t+l) ( k2 R2 4 L2)s [ exp ( k2 R2 4 H 2,1 L2) F1 ( P2;s+1; k2 R2 4 H 2,1 L2) ( H 2,1) P1]× [ exp ( k2 R2 4 H 1,1 L2) F1 ( P2;s+1; k2 R2 4 H 1,1 L2) ( H 1,1) P1+exp ( k2 R2 4 H 2,2 L2) F1 ( P2;s+1; k2 R2 4 H 2,2 L2) ( H 2,2) P1],
(20)
T2= s= t=0 [ Γ( P1)]2 γ 2t+s+l ( s!)2t!Γ ( s+t+l) ( k2 R2 4 L2)s [ exp ( k2 R2 4 H 2,1 L2) F1 ( P2;s+1; k2 R2 4 H 2,1 L2) ( H 2,1) P1]× [ exp ( k2 R2 4 H 1,2 L2) F1 ( P2;s+1; k2 R2 4 H 1,2 L2) ( H 1,2) P1+exp ( k2 R2 4 H 2,1 L2) F1 ( P2;s+1; k2 R2 4 H 2,1 L2) ( H 2,1) P1],
(21)
T3= s= t=0 [ Γ( P1)]2 γ 2t+s+l ( s!)2t!Γ ( s+t+l) ( k2 R2 4 L2)s [ exp ( k2 R2 4 H 2,2 L2) F1 ( P2;s+1; k2 R2 4 H 2,2 L2) ( H 2,2) P1]× [ exp ( k2 R2 4 H 1,2 L2) F1 ( P2 1;s+1; k2 R2 4 H 1,2 L2) ( H 1,2) P1+exp ( k2 R2 4 H 2,1 L2) F1 ( P2;s+1; k2 R2 4 H 2,1 L2) ( H 2,1) P1],
(22)
T4= s= t=0 [ Γ( P1)]2 γ 2t+s+l ( s!)2t!Γ ( s+t+l) ( k2 R2 4 L2)s [ exp ( k2 R2 4 H 2,2 L2) F1 ( P2;s+1; k2 R2 4 H 2,2 L2) ( H 2,2) P1]× [ exp ( k2 R2 4 H 1,1 L2) F1 ( P2;s+1; k2 R2 4 H 1,1 L2) ( H 1,1) P1+exp ( k2 R2 4 H 2,2 L2) F1 ( P2;s+1; k2 R2 4 H 2,2 L2) ( H 2,2) P1],
(23)
where P1=0.5l+t+s+1, P2=0.5lt, γ= 1 ρ02, H 1,1= n ω02+ Cw b2+ 1 ρ02 ik 2L, H 1,2= n ω02+ Cw a2+ 1 ρ02 ik 2L, H 2,1= n σ ω02+ Cw b2+ 1 ρ02 ik 2L, H 2,2= n σ ω02+ Cw a2+ 1 ρ02 ik 2L, H 1,1= m ω02+ Cv b2+ 1 ρ02+ ik 2L, H 1,2= m ω02+ Cv a2+ 1 ρ02+ ik 2L, H 2,1= m σ ω02+ Cv b2+ 1 ρ02+ ik 2L, H 2,2= m σ ω02+ Cv a2+ 1 ρ02+ ik 2L, Jl(.) is the l-th order Bessel function of the first kind, Il(.) is the l-th order modified Bessel function of the first kind, Γ(.) is the Gamma function and F1 ( .;.;.)is the Kummer function. Equations from Eq. (15) to Eq. (23) represent the analytical expression of the average intensity distribution at the receiver plane. Power coupling efficiency of the two-Cassegrain-telescope optical system can be expressed as
η= 2π a b <I(R,L) >RdR ab 0 2π E0(r,θ,0) E0 (r,θ,0)rdrdθ,
(24)
where a and bdenote the inner radius and the outer radius of the receiver, respectively.

3. Numerical calculations and results analysis

3.1 Average intensity distribution at the receiver plane

Parameters of the optical system are set as: the source is an ideal annular vortex beam with unit amplitude and 3.8um wavelength, the optical topological charge l=4, the dark hollow parameter σ=0.5, the source expansion order N=10, the Gaussian waist width ω0=0.2m, the inner radius of the transmitter a=0.15m, the outer radius of the transmitter b=0.40m, the expansion order of the transmitter truncation function M=16, the propagation distance L=10km and the zenith angle ξ= 30. Distribution of the atmospheric structure constant is described as the H-V 5/7 turbulence model
Cn2 (h)=8.2× 10 56V (h)2 h 10exp ( h/ 1000)+2.7× 10 16exp ( h/ 1500)+ C0exp ( h/100),
(25)
V(h)=5+30exp { [ ( h9400)/ 4800]2},
(26)
where h is the altitude from the ground, V(h) is the wind speed along the vertical path, C0is the nominal value of at ground level (the typical value is 4.0 × 10−14m-2/3).

Figure 2 shows the optical field of the annular vortex source, and the dashed lines in Fig. 2(a) represent the truncation apertures of the transmitter. After calculation, we get that 97.5% power of the annular vortex beam can pass through the transmitter telescope.

Fig. 2 The optical field of the annular vortex source: (a) intensity distribution, (b) phase distribution.

Figure 3 shows the average intensity distribution at the receiver plane, we can get that the average intensity distribution presents a central dark hollow profile. In order to show the influences of the optical topological charge, the laser wavelength, the propagation distance and the zenith angle on the average intensity distribution at the receiver plane, some numerical simulations are performed.

Fig. 3 The average intensity distribution at the receiver plane with the parameters ( l=4, λ=3.8um, σ=0.5, N=10, ω0=0.2m, L=10km, ξ= 30).

Figure 4 shows the evolution of the average intensity distribution with the increase of the optical topological charge. When l=0, the source reduces to an annular beam without vortex, optical intensity gathers on the center and the average intensity distribution presents a complex profile. When with vortex ( l1), the average intensity on the center decreases and the central dark hollow generates. Figure 4(a) shows that when l3, the width of the central dark hollow region increases with the increase of the optical topological charge, meanwhile radius of the beam spot keeps in the same. Figure 4(b) shows that with the further increase of the optical topological charge, both the width of the central dark hollow region and radius of the beam spot increases, the increment speed of the central dark hollow radius is much faster than that of the beam spot, and the peak value of the average intensity approximately keeps in equivalent.

Fig. 4 Evolution of the average intensity distribution with the increase of the optical topological charge ( λ=3.8um, σ=0.5, N=10, ω0=0.2m, L=10km, ξ= 30): (a) l3, (b) l4.

Figure 5 shows the average intensity distribution with different wavelength annular vortex sources. We can get that with the increase of the laser wavelength, optical intensity on the center decreases and the width of the central dark hollow region increases, meanwhile the beam spot spreads and the peak value of the average intensity decreases.

Fig. 5 Distribution of the average intensity with different laser wavelengths ( l=4, σ=0.5, N=10, ω0=0.2m, L=10km, ξ= 30).

Figure 6 shows the evolution of the average intensity distribution with the increase of the propagation distance. We can get that with the increase of the propagation distance, the width of the central dark region decreases, meanwhile the beam spot spreads and the peak value of the average intensity decreases.

Fig. 6 Evolution of the average intensity distribution with the increase of the propagation distance ( l=4, λ=3.8um, σ=0.5, N=10, ω0=0.2m, ξ= 30).

Figure 7 shows the evolution of the average intensity distribution as the zenith angle of the propagation path increases. We can get that with the increase of the zenith angle, power on the center increases and the central dark hollow gradually disappears, meanwhile the beam spot spreads and the peak value of the average intensity decreases. The higher the zenith angle is, the faster the increment speed of the central intensity is. When ξ= 90, the central intensity approaches to the maximum.

Fig. 7 Evolution of the average intensity distribution with the increase of the zenith angle ( l=4, λ=3.8um, σ=0.5, N=10, ω0=0.2m, L=10km).

3.2 Power coupling of the optical system

From the study above, we can get that the average intensity distribution at the receiver plane presents a central dark hollow profile, which is suitable for power coupling by the Cassegrain telescope with central obstruction and outer truncation; and parameters of the vortex source and the propagation path have great influences on the average intensity distribution. In order to show the basic characteristics of the power coupling and the influences of the parameters, we take the inner radius of the receiver a0(without the central obstruction), and perform some numerical calculations.

Figure 8 illuminates the evolution of the relations between power coupling efficiency and the receiver aperture as different parameter increases. We can get that power coupling efficiency keeps in zero at the beginning when the receiver aperture is low. Namely, when use a receiver telescope with central obscuration, power losses induced by secondary mirror obstruction can be quite low. With the increase of the receiver aperture, power coupling efficiency increases and the increment speed becomes faster. With further increases in the receiver aperture, the increment speed becomes slower and power coupling efficiency approaches to 100%. Results in Fig. 8 show that receiver aperture with zero power coupling efficiency is higher when the optical topological charge is higher, the laser wavelength is higher, the propagation distance is shorter or the zenith angle is smaller; the increment speed of the power coupling efficiency is faster when the optical topological charge is higher, the propagation distance is shorter, the zenith angle is smaller or the beam wavelength is lower.

Fig. 8 Evolution of the relations between power coupling efficiency and the receiver aperture as different parameter increases: (a) the optical topological charge, (b) the laser wavelength, (c) the propagation distance, (d) the zenith angle.

In order to show the influence of the receiver apertures on the power coupling efficiency, we take the receiver apertures “a'=0.1m, b'=0.4m”, “a'=0.12m, b'=0.5m” and “a'=0.15m, b'=0.6m” as three examples, and calculate the power coupling efficiency under determinate conditions. The coming results are listed in Table 1 .

Table 1  Power Coupling Efficiency of the Optical System with Different Receiver Apertures ( l=4, λ=3.8um, σ=0.5, N=10, ω0=0.2m, ξ= 30, a=0.15m, b=0.4m).
Receiver apertures
a' = 0.1m, b' = 0.4m
a' = 0.12m, b' = 0.5m
a' = 0.15m, b' = 0.6m
Propagation distance (km)510203051020305102030
Power efficiency (%)978864459998846899989382

Results show that power coupling efficiency of the optical system can be quite high when the propagation distance is short, and with the increase of the propagation distance, power coupling efficiency of the optical system degrades. Combing results in Fig. 8 and Table 1, we can get that parameters of the vortex source, the receiver apertures and the propagation path have great influences on the power coupling efficiency. Thus, in determining the optical system parameters, the optical topological charge, the laser wavelength, the propagation path and the receiver apertures need to be optimized to improve the power coupling efficiency. Results in Table 1 show that under the present conditions, telescope receiver with “a'=0.15m, b'=0.6m” is reasonable, and power coupling efficiency of the optical system can keep in high values with the increase of the propagation distance.

For comparison, we calculate power coupling efficiency of the optical system when using the laser source without vortex (l = 0), and the coming results are listed in Table 2 .

Table 2  ower Coupling Efficiency of the Optical System with Different Sources ( λ=3.8um, σ=0.5, N=10, ω0=0.2m, ξ= 30, a=0.15m, b=0.4m, a=0.15m, b=0.6m).
SourceAnnular beam (l = 0)Annular vortex beam (l = 4)
Propagation distance (km)51020305102030
Power efficiency (%)9589827199989382

Form the results in Table 2, we can get that power coupling efficiency of the optical system with annular vortex source is significantly higher than that of the laser source without vortex. Under the atmospheric turbulent conditions, great advantages of vortex beams are shown in power coupling of the two-Cassegrain-telescope optical system.

4. Conclusions

In this paper, we have studied power coupling of annular vortex beam propagating through a two-Cassegrain-telescope optical system in turbulent atmosphere. A typical model of annular vortex beam propagating through a two-Cassegrain-telescope optical system in turbulent atmosphere in a slant path was established, the general analytical expression of vortex beams with limited apertures and the analytical formulas for the average intensity distribution at the receiver plane were derived. Under the H-V 5/7 turbulence model, the average intensity distribution at the receiver plane and the power coupling efficiency of the optical system were numerically calculated. From the analysis we can get that the average intensity distribution at the receiver plane presents a central dark hollow profile, which is suitable for power coupling by the Cassegrain telescope receiver. Parameters of the vortex source, the receiver apertures and the propagation path have great influences on the power coupling. In the optical system with optimized parameters, power coupling efficiency can keep in high values with the increase of the propagation distance. Under the atmospheric turbulent conditions, great advantages of vortex beams in power coupling of the two-Cassegrain-telescope optical system were shown in comparison with laser source without vortex.

Acknowledgments

The authors are indebted to the National High Technology Research and Development Program of China (2012AA02007).

References and links

1.

A. Ambrosio, L. Marrucci, F. Borbone, A. Roviello, and P. Maddalena, “Light-induced spiral mass transport in azo-polymer films under vortex-beam illumination,” Nat Commun 3, 989–991 (2012). [CrossRef] [PubMed]

2.

J. Verbeeck, H. Tian, and P. Schattschneider, “Production and application of electron vortex beams,” Nature 467(7313), 301–304 (2010). [CrossRef] [PubMed]

3.

J. Ng, Z. Lin, and C. T. Chan, “Theory of optical trapping by an optical vortex beam,” Phys. Rev. Lett. 104(10), 103601 (2010). [CrossRef] [PubMed]

4.

R. Chen, L. Zhong, Q. Wu, and K. Chew, “Propagation properties and M2 factors of a vortex Airy beam,” Opt. Laser Technol. 44(7), 2015–2019 (2012). [CrossRef]

5.

G. Gallatin and B. McMorran, “Propagation of vortex electron wave functions in a magnetic field,” Phys. Rev. A 86(1), 012701 (2012). [CrossRef]

6.

C. Kamacıoğlu and Y. Baykal, “Generalized expression for optical source fields,” Opt. Laser Technol. 44(6), 1706–1712 (2012). [CrossRef]

7.

V. P. Lukin, P. A. Konyaev, and V. A. Sennikov, “Beam spreading of vortex beams propagating in turbulent atmosphere,” Appl. Opt. 51(10), C84–C87 (2012). [CrossRef] [PubMed]

8.

G. Fang, W. Zhu, X. Chen, and J. Pu, “Propagation of partially coherent double-vortex beams in turbulent atmosphere,” Opt. Laser Technol. 44(6), 1780–1785 (2012). [CrossRef]

9.

H. T. Dai, Y. J. Liu, D. Luo, and X. W. Sun, “Propagation properties of an optical vortex carried by an Airy beam: experimental implementation,” Opt. Lett. 36(9), 1617–1619 (2011). [CrossRef] [PubMed]

10.

X. Chu and G. Zhou, “Power coupling of a two-Cassegrain-telescopes system in turbulent atmosphere in a slant path,” Opt. Express 15(12), 7697–7707 (2007). [CrossRef] [PubMed]

11.

H. Wu, W. Wu, X. Xu, J. Chen, and Y. Zhao, “A new method to improve power efficiencies of optical systems with Cassegrain-telescope receivers,” Opt. Commun. 284(13), 3361–3364 (2011). [CrossRef]

12.

G. Ren, “Current situation and development trend of high energy laser weapon,” Laser Optoelectronics Prog. 45(9), 62–69 (2008). [CrossRef]

13.

J. Simpson, “Tactical laser relay mirror demonstration anticipated before 2011,” Inside the Air Force 18, 3-7 (2007).

14.

H. Wu, Z. Sun, and J. Chen, “Improving performances of the optical systems with Cassegrain-telescope receivers by using vortex sources and phase optimizations,” Opt. Laser Technol. 45, 132–136 (2013). [CrossRef]

15.

H. Ma, Z. Liu, H. Wu, X. Xu, and J. Chen, “Adaptive correction of vortex laser beam in a closed-loop system with phase only liquid crystal spatial light modulator,” Opt. Commun. 285(6), 859–863 (2012). [CrossRef]

16.

Z. Mei, D. Zhao, and J. Gu, “Comparison of two approximate methods for hard-edged diffracted flat-topped light beams,” Opt. Commun. 267(1), 58–64 (2006). [CrossRef]

17.

H. Mao and D. Zhao, “Different models for a hard-aperture function and corresponding approximate analytical propagation equation of a Gaussian beam through an apertured optical system,” J. Opt. Soc. Am. A 22(4), 647–653 (2005). [CrossRef]

18.

G. Zhou, Y. Cai, and X. Chu, “Propagation of a partially coherent hollow vortex Gaussian beam through a paraxial ABCD optical system in turbulent atmosphere,” Opt. Express 20(9), 9897–9910 (2012). [CrossRef] [PubMed]

19.

H. T. Eyyuboglu, C. Arpali, and Y. K. Baykal, “Flat topped beams and their characteristics in turbulent media,” Opt. Express 14(10), 4196–4207 (2006). [CrossRef] [PubMed]

20.

C. Arpali, C. Yazıcıoğlu, H. T. Eyyuboğlu, S. A. Arpali, and Y. Baykal, “Simulator for general-type beam propagation in turbulent atmosphere,” Opt. Express 14(20), 8918–8928 (2006). [CrossRef] [PubMed]

21.

X. Liu and J. Pu, “Investigation on the scintillation reduction of elliptical vortex beams propagating in atmospheric turbulence,” Opt. Express 19(27), 26444–26450 (2011). [CrossRef] [PubMed]

OCIS Codes
(010.1300) Atmospheric and oceanic optics : Atmospheric propagation
(010.3310) Atmospheric and oceanic optics : Laser beam transmission

ToC Category:
Atmospheric and Oceanic Optics

History
Original Manuscript: November 7, 2012
Revised Manuscript: December 15, 2012
Manuscript Accepted: January 23, 2013
Published: February 11, 2013

Citation
Huiyun Wu, Shen Sheng, Zhisong Huang, Siqing Zhao, Hua Wang, Zhenhai Sun, and Xiegu Xu, "Study on power coupling of annular vortex beam propagating through a two-Cassegrain-telescope optical system in turbulent atmosphere," Opt. Express 21, 4005-4016 (2013)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-21-4-4005


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References

  1. A. Ambrosio, L. Marrucci, F. Borbone, A. Roviello, and P. Maddalena, “Light-induced spiral mass transport in azo-polymer films under vortex-beam illumination,” Nat Commun3, 989–991 (2012). [CrossRef] [PubMed]
  2. J. Verbeeck, H. Tian, and P. Schattschneider, “Production and application of electron vortex beams,” Nature467(7313), 301–304 (2010). [CrossRef] [PubMed]
  3. J. Ng, Z. Lin, and C. T. Chan, “Theory of optical trapping by an optical vortex beam,” Phys. Rev. Lett.104(10), 103601 (2010). [CrossRef] [PubMed]
  4. R. Chen, L. Zhong, Q. Wu, and K. Chew, “Propagation properties and M2 factors of a vortex Airy beam,” Opt. Laser Technol.44(7), 2015–2019 (2012). [CrossRef]
  5. G. Gallatin and B. McMorran, “Propagation of vortex electron wave functions in a magnetic field,” Phys. Rev. A86(1), 012701 (2012). [CrossRef]
  6. C. Kamacıoğlu and Y. Baykal, “Generalized expression for optical source fields,” Opt. Laser Technol.44(6), 1706–1712 (2012). [CrossRef]
  7. V. P. Lukin, P. A. Konyaev, and V. A. Sennikov, “Beam spreading of vortex beams propagating in turbulent atmosphere,” Appl. Opt.51(10), C84–C87 (2012). [CrossRef] [PubMed]
  8. G. Fang, W. Zhu, X. Chen, and J. Pu, “Propagation of partially coherent double-vortex beams in turbulent atmosphere,” Opt. Laser Technol.44(6), 1780–1785 (2012). [CrossRef]
  9. H. T. Dai, Y. J. Liu, D. Luo, and X. W. Sun, “Propagation properties of an optical vortex carried by an Airy beam: experimental implementation,” Opt. Lett.36(9), 1617–1619 (2011). [CrossRef] [PubMed]
  10. X. Chu and G. Zhou, “Power coupling of a two-Cassegrain-telescopes system in turbulent atmosphere in a slant path,” Opt. Express15(12), 7697–7707 (2007). [CrossRef] [PubMed]
  11. H. Wu, W. Wu, X. Xu, J. Chen, and Y. Zhao, “A new method to improve power efficiencies of optical systems with Cassegrain-telescope receivers,” Opt. Commun.284(13), 3361–3364 (2011). [CrossRef]
  12. G. Ren, “Current situation and development trend of high energy laser weapon,” Laser Optoelectronics Prog.45(9), 62–69 (2008). [CrossRef]
  13. J. Simpson, “Tactical laser relay mirror demonstration anticipated before 2011,” Inside the Air Force 18, 3-7 (2007).
  14. H. Wu, Z. Sun, and J. Chen, “Improving performances of the optical systems with Cassegrain-telescope receivers by using vortex sources and phase optimizations,” Opt. Laser Technol.45, 132–136 (2013). [CrossRef]
  15. H. Ma, Z. Liu, H. Wu, X. Xu, and J. Chen, “Adaptive correction of vortex laser beam in a closed-loop system with phase only liquid crystal spatial light modulator,” Opt. Commun.285(6), 859–863 (2012). [CrossRef]
  16. Z. Mei, D. Zhao, and J. Gu, “Comparison of two approximate methods for hard-edged diffracted flat-topped light beams,” Opt. Commun.267(1), 58–64 (2006). [CrossRef]
  17. H. Mao and D. Zhao, “Different models for a hard-aperture function and corresponding approximate analytical propagation equation of a Gaussian beam through an apertured optical system,” J. Opt. Soc. Am. A22(4), 647–653 (2005). [CrossRef]
  18. G. Zhou, Y. Cai, and X. Chu, “Propagation of a partially coherent hollow vortex Gaussian beam through a paraxial ABCD optical system in turbulent atmosphere,” Opt. Express20(9), 9897–9910 (2012). [CrossRef] [PubMed]
  19. H. T. Eyyuboglu, C. Arpali, and Y. K. Baykal, “Flat topped beams and their characteristics in turbulent media,” Opt. Express14(10), 4196–4207 (2006). [CrossRef] [PubMed]
  20. C. Arpali, C. Yazıcıoğlu, H. T. Eyyuboğlu, S. A. Arpali, and Y. Baykal, “Simulator for general-type beam propagation in turbulent atmosphere,” Opt. Express14(20), 8918–8928 (2006). [CrossRef] [PubMed]
  21. X. Liu and J. Pu, “Investigation on the scintillation reduction of elliptical vortex beams propagating in atmospheric turbulence,” Opt. Express19(27), 26444–26450 (2011). [CrossRef] [PubMed]

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