电光可调谐矩形阵列光源：基于周期极化铌酸锂晶体的实验实现

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"Tunable rectangular array illuminator in periodically poled LiNbO3 crystal" 这篇研究文章介绍了一种基于周期性极化铌酸锂(LiNbO3)晶体的电光可调谐矩形阵列照明器的实验实现。该照明器利用了Talbot自成像效应，通过在PPLN晶体上施加电场来形成。实验结果与模拟结果吻合良好，展示了对矩形阵列强度分布的精确调制能力。 Talbot效应是一种光学现象，当光线通过一个周期性结构的光栅后，经过特定距离会自我复制出与原光栅相同的空间频率分布。在本文中，这个效应被用来在PPLN晶体中生成矩形阵列的照明模式。周期性极化的LiNbO3晶体具有电光效应，即电场可以改变其折射率，从而影响通过晶体的光束的相位，进而调控光的分布。与传统的阵列照明器相比，这种可调谐的矩形阵列照明器有显著优势。首先，它只需要较低的电压就能实现调制，这意味着更节能和操作简便。其次，它能产生更为集中的光强分布，这对于需要高密度光束的应用（如激光加工、光刻技术或者精密测量）尤其有利。文章还讨论了入射光的特性如何影响照明器的性能，包括波长、入射角度以及电场强度等因素。这些因素的调整能够进一步优化照明器的光强分布，使得研究人员能够在不同的应用条件下定制光束模式。此外，该研究可能对光纤通信网络、高级光学通信系统等领域产生影响，因为可调谐的光束分布对于光信号处理和光信息传输至关重要。上海交通大学的国家重点实验室在这个领域进行了深入研究，并且取得了显著成果。这项工作不仅展示了创新的光电器件设计，还为光电子学领域的研究提供了新的思路和技术手段，有望推动光电技术的进步，特别是在高精度光学系统和低功耗设备中的应用。

COL 12(5), 050701(2014) CHINESE OPTICS LETTERS May 10, 2014

Tunable rectangular array illuminator in periodically poled

LiNbO

crystal

Qiuying Li (ooo¢¢¢LLL), Juan Huo (¿¿¿ ïïï), Xiaohui Zhao (ëëë¡¡¡zzz), and Xianfeng Chen (xxx¸¸¸)

∗

State Key Laboratory on Fiber Optic Local Area Communication Networks and Advanced Optical Communication Systems,

Department of Physics, Shanghai Jiao Tong University, Shanghai 200240, China

∗

Corresponding author: xfchen@sjtu.edu.cn

Received December 29, 2013; accepted March 27, 2014; posted online April 30, 2014

An electro-optic tunable rectangular array illuminator in one-dimensional periodically poled LiNbO

(PPLN) crystal is presented experimentally which result is in good agreement with results from simu-

lation. The illuminator is formed based on the Talbot self-imaging eﬀect by applying an electric ﬁeld

on PPLN. The intensity distribution of rectangular array could be precisely modulated. Compared with

other array illuminators, this tunable illuminator uses a lower voltage and could get a more concentrated

intensity distribution. The inﬂuence of the incident angle to the self-imaging patterns is studied for the

ﬁrst time.

OCIS codes: 070.6760, 160.2100.

doi: 10.3788/COL201412.050701.

Array illuminator is a devic e that transforms laser beam

into patterns with periodical optical intensity and is

widely used in processing and synthesis, photolithog-

raphy, optical testing, optical metrology, spectro metr y,

optical computing, as well as in electron optics and

microscopy

[1−3]

. Although several schemes have been

proposed for implementing array illuminators, the fa -

vorite method is Talbo t eﬀect. It is a near-ﬁeld diﬀraction

phenomenon in which self-imaging of a grating or other

periodic structure replicates at certa in imaging planes,

was found by Talbot et al.

[4−6]

In this letter, we realized a rectangular array illumi-

nator that was ma de by a phase g rating which was a

one-dimensional (1D) periodically p oled LiNbO

(PPLN)

with an external electric ﬁeld. The PPLN was for med

through fer roelectric domain inversion technology

[7]

, the

nonlinear optical coeﬃcient and the electr o-optic (EO)

coeﬃcient are modulated periodically. Based on this

structure, essential applications such as quasi-phase-

matching

[8]

, wavelength conversion

[9]

, narrow band solc-

type ﬁlters

[10,11]

, polarization controllers

[12,13]

, opti-

cal vortex

[14]

, all-optical logic gates.[15], waveguide

[16]

and laser Q -switch

[17]

have been successfully demon-

strated. Compared with other electro-optic phase

illuminators

[18,19]

, there are some impo rtant features of

our device. In our experiment the light was chosen to

propagate parallel to the y axis and the direction of polar-

ization was along the z axis. These speciﬁc arrangements

increased the phase delay betwe e n positive domains and

negative domains, consequently, the relevant modulat-

ing voltage became lower. The increased external elec-

tric ﬁeld will induce the decrease in width of bright ar-

eas in the self-imaging patterns, method to acquir e more

concentrated distribution of intensity was proposed. We

studied the self-imaging patterns at diﬀerent incident an-

gles. Some interesting patterns were recorded, such as

the chirp intensity distribution.

Beneﬁtting fr om the modulation of EO coeﬃcient and

the reversal of the ferroelectric, the phase changes pe -

riodically on the output surface after applying an elec-

tric ﬁeld along the z axis of PPLN. A rectangular phase

grating with periodic structures is formed. As mentioned

befo re, the Talbot eﬀect can be found attributed to the

interference of diﬀracted beams from periodic structures.

In the ex periment, as mentioned before, the light propa-

gated along the y axis and the direction of polarization

paralleled to the z axis (extraordinary light). The change

of refractive index and phase in domains can be written

[20]

∆n = ±

, (1)

∆φ =

∆n

2πλ

, (2)

where n

is refractive index of extraordinary light without

electric ﬁeld, γ

is linear electro-optic coeﬃcient of the

lithium niobate crystal, l

is the length along the y direc-

tion of PPLN, and E

is the electric ﬁeld strength applied

on the z direction. In PPLN, γ

is nearly three times as

large a s γ

, and the latter will appear when the ordinary

light is chosen as Eq. (1) turns to be ∆n = ±1/2n

And because of limit of domain inversion technology, the

length of PPLN along the z axis is short, the maximum

is 1 mm in general, however the length along the y di-

rection could be manufactured to be cons iderably long.

Here we chose l

= 3 mm. Consequently, compar e d with

other electro-optic phase illuminators, our case could use

an extremely low elec tric ﬁeld to get a prospective phase

delay.

The transmittance function of this phase grating is

given by

t(x, y) =



i∆φ

− e

−i∆φ

)rect





∗

comb





i∆φ

(3)

where ∗ repres e nts convolution and a is the period o f

grating. The transfer function of Fresnel diﬀraction can

be written as

h(x, y) =

exp(ikz)

iλz

exp



+ y

)



, (4)

1671-7694/2014/050701(4) 050701-1

 2014 Chinese Optics Letters

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