广义厄尔米特–双曲余弦–高斯光束在手性介质中的传播特性
Propagation Properties of Generalized Hermite-Hyperbolic Cosine-Gaussian Beams in Chiral Media
摘要: 本文基于惠更斯–菲涅耳积分公式,推导出了广义厄尔米特–双曲余弦–高斯光束在手性介质中传输的解析表达式,并以此为基础,对该光束在手性介质中的传播规律进行了详细的数值计算。研究结果表明,手性介质参数和光束的源参数对广义厄尔米特–双曲余弦–高斯光束在手性介质中的传输特性产生影响。我们的研究有助于加深对这种光束与手性介质之间的相互作用的理解。
Abstract: In this paper, based on Huygens-Fresnel integral formula, an analytical expression for a generalized Hermite-Hyperbolic Cosine-Gaussian beam propagating in chiral media is derived. Based on this, the propagation properties of such beams are researched numerically in detail in chiral media. The research results indicate that the chiral medium parameter and the beam source parameters have an impact on the propagation properties of the generalized Hermite-Hyperbolic Cosine-Gaussian beam in chiral media. Our research is beneficial to a further understanding of the interaction between the beam and chiral media.
文章引用:王金霞, 龙林, 赵玉娟. 广义厄尔米特–双曲余弦–高斯光束在手性介质中的传播特性[J]. 现代物理, 2024, 14(5): 206-214. https://doi.org/10.12677/mp.2024.145024

1. 前言

光学领域中材料的几何不对称性会导致一种被称为手性特性的现象,这种材料是由具有各向异性结构的不对称材料组成,当光波照射这些介质时,光的传播出现各向异性,展现出负折射、圆二色性和偏振旋转等特性[1] [2]。在非线性光学、生物化学和医学等各个领域具有潜在的应用前景[3]-[5]。近年来,各种激光光束在手性介质中的传播特性引起了人们广泛的兴趣[6]-[10]。1997年,Casperson等提出了复杂光学系统中傍轴波的解集,称为厄尔米特–双曲正弦–高斯(HSG)光束[3],用它来描述光学系统中传播的各种光束。后来,人们针对这些光束在各种介质中的传播开始研究,如涡旋光束在手性介质中的传播特性[11]-[14]、高斯光束在手性介质中的传播[15]-[18],以及这些光束在光学系统中传播的研究层出不穷[19]-[25]。最近,有学者提出了广义厄尔米特–双曲余弦–高斯(GHCG)光束[15],这类光束具有一些不同于厄尔米特–双曲正弦–高斯光束的特性,引起研究者的广泛关注。到目前为止,有关GHCG在手性介质的传播鲜为报道。

因此,本文在前人工作的基础上,利用惠更斯–菲涅耳衍射积分推导出GHCG光束在手性介质中的传播公式,并通过数值分析来揭示GHCG光束在手性介质中的传播行为。

2. GHCG光束在手性介质中的解析传播表达式

假设GHCG光束在手性介质z轴作为传播方向(z > 0)传播,则光束在源平面z = 0处的场表达式可以写成[14]

E ( x 0 , y 0 , z = 0 ) = E 0 ( x 0 y 0 w 2 ) l h u ( α x 0 ) h v ( α y 0 ) cosh m ( Ω x 0 ) cosh m ( Ω y 0 ) exp ( x 0 2 + y 0 2 w 2 ) , (1)

其中, α = 2 / w w表示高斯光束宽度,E0代表光场振幅,Ω是与cosh函数相关的位移参数, h u ( . ) h v ( . ) 分别表示第u阶、v阶Hermite多项式。将方程(1)通过级数变换,可化简为:

E ( x 0 , y 0 , z = 0 ) = E 0 2 2 m ( x 0 y 0 w 2 ) l h u ( α x 0 ) h v ( α y 0 ) r = 0 m ( m r ) e b r 2 ξ exp [ ( x 0 w b r ξ ) 2 ] q = 0 m ( m q ) e b q 2 ξ exp [ ( y 0 w b q ξ ) 2 ] , (2)

其中, ξ = w 2 Ω 2 b r = ( r m / 2 ) b q = ( q m / 2 )

根据惠更斯–菲涅耳衍射积分,GHCG光束在近轴ABCD光学系统传播中任一点场分布[26]

E ( x , y , z ) = i k 2 π B e i k z + + E 0 ( x 0 , y 0 , 0 ) × exp { i k 2 B [ A ( x 0 2 + y 0 2 ) 2 ( x x 0 + y y 0 ) + D ( x 2 + y 2 ) ] } d x 0 d y 0 , (3)

其中,ABD代表光学系统传递矩阵的元素,波数 k = 2 π λ ,其中λ代表光波波长。

将等式(2)代入等式(3),并利用积分公式[26]

x s e α ρ 2 + 2 Q ρ h h ( β ρ ) d ρ = 1 2 s π α exp ( Q 2 α ) m = 0 [ h / 2 ] ( 1 ) m h ! m ! ( h 2 m ) ! h h + s 2 m ( i Q α ) ( β i α ) h + s 2 m , (4)

经过化简可得:

E ( x , y , z ) = i k A 0 e i k z 2 2 m + 2 l + 1 B w 2 l ( π β ) exp [ i k D 2 B ( x 2 + y 2 ) ] r = 0 m q = 0 m ( m r ) ( m q ) × exp ( Q x 2 β + Q y 2 β ) k 1 [ n / 2 ] k 2 [ n / 2 ] ( 1 ) k 1 + k 2 u ! v ! k 1 ! k 2 ! ( u 2 k 1 ) ! ( v 2 k 2 ) ! × ( α i β ) u + l 2 k 1 ( α i β ) v + l 2 k 2 h u + l 2 k 1 ( i Q x β ) h v + l 2 k 2 ( i Q y β ) , (5)

其中,

β = 1 w 2 + i k A 2 B , Q x = b r n ξ w + i k x 2 B , Q y = b q n ξ w + i k y 2 B . (6)

假设穿过手性介质的入射光为线性偏振GHCG光束。由于介质的手性,入射的GHCG光场将分裂为左圆偏振光和右圆偏振光。由于两束光在介质中的折射率不同而以不同的相速度传播,在手性介质中nRnL可表示为:

n L = n 0 / ( 1 + n 0 k γ ) , n R = n 0 / ( 1 n 0 k γ ) . (7)

其中,γ代表手性参数,n0表示手性介质的原始折射率。在手性介质中,与左圆偏振光和右圆偏振光相对应的ABCD矩阵表示为[8] [9]

{ ( A L B L C L D L ) = ( 1 z / n L 0 1 ) , ( A R B R C R D R ) = ( 1 z / n R 0 1 ) . (8)

将等式(8)应用于等式(5),可以得到左旋圆偏振光和右旋圆偏振光的表达式:

E L ( x , y , z ) = i k E 0 e i k z 2 2 m + 2 l + 1 B L w 2 l ( π β L ) exp [ i k D 2 B L ( x 2 + y 2 ) ] r = 0 m q = 0 m ( m r ) ( m q ) × exp ( Q x 2 β L + Q y 2 β L ) k 1 [ n / 2 ] k 2 [ n / 2 ] ( 1 ) k 1 + k 2 u ! v ! k 1 ! k 2 ! ( u 2 k 1 ) ! ( v 2 k 2 ) ! × ( α i β L ) u + l 2 k 1 ( α i β L ) v + l 2 k 2 h u + l 2 k 1 ( i Q x β L ) h v + l 2 k 2 ( i Q y β L ) , (9)

E R ( x , y , z ) = i k E 0 e i k z 2 2 m + 2 l + 1 B R w 2 l ( π β R ) exp [ i k D 2 B R ( x 2 + y 2 ) ] r = 0 m q = 0 m ( m r ) ( m q ) × exp ( Q x 2 β R + Q y 2 β R ) k 1 [ n / 2 ] k 2 [ n / 2 ] ( 1 ) k 1 + k 2 u ! v ! k 1 ! k 2 ! ( u 2 k 1 ) ! ( v 2 k 2 ) ! × ( α i β R ) u + l 2 k 1 ( α i β R ) v + l 2 k 2 h u + l 2 k 1 ( i Q x β R ) h v + l 2 k 2 ( i Q y β R ) , (10)

其中, β j = 1 w 2 + i k A 2 B j Q x , j = b r n ξ w + i k x 2 B j Q y , j = b q n ξ w + i k y 2 B j j = L , R

因此,GHCG光束在手性介质中的电场可以表示为:

E ( x , y , z ) = E L ( x , y , z ) + E R ( x , y , z ) ,(11)

并且总光强为:

I = | E L ( x , y , z ) | 2 + | E R ( x , y , z ) | 2 + I 0 ,(12)

其中,干涉项 I 0 为:

I 0 ( x , y , z ) = E L ( x , y , z ) E R ( x , y , z ) + E L ( x , y , z ) E R ( x , y , z ) .(13)

其中,“*”代表复共轭。利用方程(11)~(13)可以方便地进行数值计算,用来模拟GHCG光束在手性介质中的传播规律。

3. 数值计算与分析

应用上述解析表达式,我们可以研究不同参数下GHCG光束在手性介质中的传播特性。通过改变源光束参数和手性介质的参数,对GHCG光束在手性介质中传播的光强分布进行分析讨论。计算时设置源光束参数为:u = 1,v = 1,l = 1,m = 2,w = 1 mm,λ = 632.8 nm,手性介质的参数为:n0 = 3,γ = 0.16/k。这里,我们将光强归一化并通过瑞利长度zR缩放传播距离。

图1给出了GHCG光束通过手性参数γ = 0.16/k的介质时在不同传播距离处左圆偏振光光强IL(z)和右圆偏振光光强IR(z)及总光强I(z)的分布。从图中可以看出,入射光束在源平面处,左圆偏振光场和右圆偏振光场的光强分布和总光束均保持其暗空心分布不变。当传输距离增大时,左圆偏振光场和右圆偏振光场的光强分布非同步变化,中心暗斑都逐渐消失,中心光强逐渐增大并且被弱亮环包围着。而干涉项产生的光强分布,在传播衰减时出现二次旁瓣峰,并在远场区域保持其分布不变。从总光强度二维伪真彩图分布还可以看出,该光束的总光强在近场区为对称的四瓣分布,随着传输距离的增大,光强分布发生复杂的变化,在远场时,其中心分布保持高斯分布并被四瓣弱斑对称地包围着。

图2给出了GHCG光束在不同阶次下在传输距离z = 5zR处左旋圆偏振光、右旋圆偏正光及其总光强分布。从图2可以看出,对于手性参数γ = 0.16/k的介质,当光束阶次uv等于1时,左旋园偏振光的光强分布是呈现出由多瓣弱光斑包围的类高斯分布光束,而右旋园偏振光的光强由强度不一的多瓣构成,由于手性参数γ的影响,最终总的光强向中心集中(a1~c1)。此外,我们发现,改变光束的阶次uv不会影响对称性,但会改变光束旁瓣的分布。随着光束阶次uv逐渐增大,我们发现,当u = 2,v = 1时,沿x轴方向左右出现中心双瓣(a2~c2),这表明与y轴相比,光束沿x轴的传播更快。相反,当u = 1,v = 2时,我们看到,光强分布沿y轴方向左右出现中心双瓣(a3~c3)。当光束阶次u = v = 2时,光强分布演变为中心的四瓣分布(a4~c4)。

Figure 1. Normalized light intensity distribution of GHCG beams propagating over different distances in chiral media (γ = 0.16/k, Ω = 0.1 mm−1)

1. GHCG光束在手性介质中传播不同距离时归一化光强分布(γ = 0.16/k,Ω = 0.1 mm−1)

Figure 2. Normalized light intensity distribution of GHCG beams of different orders at the medium propagation distance z = 5zR with chiral parameter γ = 0.16/k

2. 不同阶次的GHCG光束在手性参数γ = 0.16/k的介质传播距离z = 5zR处的归一化光强分布

为了进一步分析手性参数γ对光束的影响,我们在图3中给出了手性参数γ = 0.28/k时GHCG光束在传输距离z = 5zR处左旋圆偏振光、右旋圆偏正光及其总光强分布。与图2光强分布相比,随着γ的增加,可以发现左旋圆偏振光束光强分布范围向外扩展。而右旋圆偏振光束光强分布与图2中右旋圆偏振光光强分布有着明显的区别,很明显,手性参数对右旋圆偏振光光强分布影响更为敏感。由此可以看出,光束阶数和手性参数对光束的光强分布有很大影响。

图4分析了不同手性参数γ对不同宽度光束的光强分布的影响,从图中可以看出,对于两个不同手性参数的介质,光束宽度较大的光束的左旋圆偏振光、右旋园偏振光及其总光强分布较为相似。而光束宽度较小的光束的左旋圆偏振光束出现具有小亮环的中心亮强度,并且与右旋圆偏振光束的强度分布不同,但随着γ的增加,暗空心中心变得更加明显。

最后,我们分析偏心参数Ω对光束传播的影响,图5给出了不同偏心参数的GHCG光束在两种不同手性参数介质中给定传输距离处的光强分布曲线。从图中可以看出,偏心参数Ω对入射光束的光强演变影响较大。随着偏心参数Ω的增大,光强分布向外迅速扩展,中心亮斑逐渐减弱。并且手性参数对光强的演化产生明显的影响。特别是光束的偏心参数Ω较小时,手性参数γ对光强分布影响较为显著。

Figure 3. Normalized light intensity distribution of GHCG beams of different orders at the medium propagation distance z = 5zR with chiral parameter γ = 0.28/k

3. 不同阶次的GHCG光束在手性参数γ = 0.28/k的介质传播距离z = 5zR处的归一化光强分布

Figure 4. Normalized light intensity distribution at distance z = 3zR for GHCG beams with different beam widths when propagating in two different chiral media: (a1~c1) γ = 0.16/k; (a2~c2) γ = 0.28/k

4. 不同光束宽度的GHCG光束在两种不同手性介质中传播时距离z = 3zR处的归一化光强分布:(a1~c1) γ = 0.16/k;(a2~c2) γ = 0.28/k

Figure 5. Normalized light intensity distribution of GHCG beam propagating in z = 3zR chiral media with different eccentricity parameters: (a1~c1) γ = 0.16/k; (a2~c2) γ = 0.28/k

5. 不同偏心参数的GHCG光束在z = 3zR手性介质中传播的归一化光强分布:(a1~c1) γ = 0.16/k;(a2~c2) γ = 0.28/k

4. 结论

基于ABCD传递矩阵和惠更斯–菲涅耳积分,我们给出了广义厄尔米特–双曲余弦–高斯光束在手性介质中传播的解析表达式,并且通过数值计算详细分析了光束在手性介质中的传播特性。研究结果表明,手性参数和光束参数对GHCG光束在手性介质中的传播起决定作用。

参考文献

[1] Aggarwal, M., Vij, S. and Kant, N. (2014) Propagation of Cosh Gaussian Laser Beam in Plasma with Density Ripple in Relativistic-Ponderomotive Regime. Optik, 125, 5081-5084.
https://doi.org/10.1016/j.ijleo.2014.04.098
[2] Pendry, J.B. (2004) A Chiral Route to Negative Refraction. Science, 306, 1353-1355.
https://doi.org/10.1126/science.1104467
[3] Casperson, L.W., Hall, D.G. and Tovar, A.A. (1997) Sinusoidal-Gaussian Beams in Complex Optical Systems. Journal of the Optical Society of America A, 14, 3341-3348.
https://doi.org/10.1364/josaa.14.003341
[4] Chern, R. and Chang, P. (2013) Negative Refraction and Backward Wave in Chiral Mediums: Illustrations of Gaussian Beams. Journal of Applied Physics, 113, Article ID: 153504.
https://doi.org/10.1063/1.4800864
[5] Deng, F., Yu, W., Huang, J., Zhao, R., Lin, J. and Deng, D. (2016) Propagation of Airy-Gaussian Beams in a Chiral Medium. The European Physical Journal D, 70, Article No. 87.
https://doi.org/10.1140/epjd/e2016-60677-8
[6] Hricha, Z. and Belafhal, A. (2005) Focusing Properties and Focal Shift in Hyperbolic-Cosine-Gaussian Beams. Optics Communications, 253, 242-249.
https://doi.org/10.1016/j.optcom.2005.04.081
[7] Hricha, Z., Yaalou, M. and Belafhal, A. (2021) Paraxial Propagation and Focusing of Higher-Order Cosh-Gaussian Beams. Journal of Modern Optics, 68, 742-752.
https://doi.org/10.1080/09500340.2021.1945156
[8] Hua, S., Liu, Y., Zhang, H., Tang, L. and Feng, Y. (2017) Propagation of an Airy-Gaussian-Vortex Beam in a Chiral Medium. Optics Communications, 388, 29-37.
https://doi.org/10.1016/j.optcom.2016.11.001
[9] Hui, Y., Cui, Z., Li, Y., Zhao, W. and Han, Y. (2018) Propagation and Dynamical Characteristics of a Bessel-Gaussian Beam in a Chiral Medium. Journal of the Optical Society of America A, 35, 1299-1305.
https://doi.org/10.1364/josaa.35.001299
[10] Kwon, D., Werner, P.L. and Werner, D.H. (2008) Optical Planar Chiral Metamaterial Designs for Strong Circular Dichroism and Polarization Rotation. Optics Express, 16, 11802-11807.
https://doi.org/10.1364/oe.16.011802
[11] Liu, X. and Zhao, D. (2014) Propagation of a Vortex Airy Beam in Chiral Medium. Optics Communications, 321, 6-10.
https://doi.org/10.1016/j.optcom.2014.01.068
[12] Saad, F. and Belafhal, A. (2022) Investigation on Propagation Properties of a New Optical Vortex Beam: Generalized Hermite-Cosh-Gaussian Beam. Optical and Quantum Electronics, 55, Article No. 83.
https://doi.org/10.1007/s11082-022-04292-5
[13] Xie, J., Zhang, J., Ye, J., Liu, H., Liang, Z., Long, S., et al. (2018) Paraxial Propagation of the First-Order Chirped Airy Vortex Beams in a Chiral Medium. Optics Express, 26, 5845-5856.
https://doi.org/10.1364/oe.26.005845
[14] Yang, X., Wu, Z. and Qu, T. (2020) Paraxial Propagation of Cosh-Airy Vortex Beams in Chiral Medium. Chinese Physics B, 29, Article ID: 034201.
https://doi.org/10.1088/1674-1056/ab683f
[15] Moshkelgosha, M. (2019) Controlling the Relativistic Self-Focusing of Hermite-Cosh-Gaussian Beams in Plasma. Optik, 182, 80-87.
https://doi.org/10.1016/j.ijleo.2018.12.190
[16] Qiu, Y. and Liu, Z. (2024) Propagation of Tricomi-Gaussian Beams in a Chiral Medium. Results in Physics, 58, Article ID: 107457.
https://doi.org/10.1016/j.rinp.2024.107457
[17] Yaalou, M., Hricha, Z. and Belafhal, A. (2023) Paraxial Propagation of Hermite Cosine-Hyperbolic-Gaussian Beams in a Chiral Medium. Optical and Quantum Electronics, 55, Article No. 1281.
https://doi.org/10.1007/s11082-023-05585-z
[18] Zeng, Z. and Deng, D. (2019) Paraxial Propagation of Pearcey Gaussian Beams with the Astigmatic Phase in the Chiral Medium. Journal of the Optical Society of America B, 37, 30-37.
https://doi.org/10.1364/josab.37.000030
[19] Tang, B., Li, Z., Palacios, E., Liu, Z., Butun, S. and Aydin, K. (2017) Chiral-Selective Plasmonic Metasurface Absorbers Operating at Visible Frequencies. IEEE Photonics Technology Letters, 29, 295-298.
https://doi.org/10.1109/lpt.2016.2647262
[20] Wang, W., Mi, Z., Zhang, L., Wang, B., Han, K., Lei, C., et al. (2023) The Abruptly Autofocusing Characteristics of the Circular Airyprime Beam in a Chiral Medium. Optics Communications, 549, Article ID: 129879.
https://doi.org/10.1016/j.optcom.2023.129879
[21] Zhang, S., Park, Y., Li, J., Lu, X., Zhang, W. and Zhang, X. (2009) Negative Refractive Index in Chiral Metamaterials. Physical Review Letters, 102, Article ID: 023901.
https://doi.org/10.1103/physrevlett.102.023901
[22] Zhang, Y., Wang, L. and Zhang, Z. (2017) Circular Dichroism in Planar Achiral Plasmonic L-Shaped Nanostructure Arrays. IEEE Photonics Journal, 9, 1-7.
https://doi.org/10.1109/jphot.2017.2670783
[23] Zhou, G. and Liu, F. (2008) Far Field Structural Characteristics of Cosh-Gaussian Beam. Optics & Laser Technology, 40, 302-308.
https://doi.org/10.1016/j.optlastec.2007.05.004
[24] Zhuang, F., Du, X. and Zhao, D. (2011) Polarization Modulation for a Stochastic Electromagnetic Beam Passing through a Chiral Medium. Optics Letters, 36, 2683-2685.
https://doi.org/10.1364/ol.36.002683
[25] Collins, S.A. (1970) Lens-System Diffraction Integral Written in Terms of Matrix Optics. Journal of the Optical Society of America, 60, 1168-1177.
https://doi.org/10.1364/josa.60.001168
[26] Gradshteyn, I.S. and Ryzhik, I.M. (1994) Tables of Integrals, Series, and Product. 5th Edition, Academic Press.

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