Generation of an ultra-long sub-diffracted second-harmonic optical needle from a periodically poled LiNbO3 crystal

We experimentally demonstrate the use of a periodically poled LiNbO3 (PPLN) crystal to produce an ultra-long sub-diffraction optical needle via second-harmonic generation. When we input a radially polarized fundamental wave from a femtosecond laser, a sub-diffraction beam size of 0.45λSH and an ultr...

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Bibliographic Details
Published in:Applied physics letters 2020-02, Vol.116 (8)
Main Authors: Zhu, Yunzhi, Wang, Huijun, Zhang, Yihong, Liu, Dongmei, Zhong, Weihao, Gao, Zhida, Cui, Guoxin, Lu, Yanqing, Zhang, Yong, Xiao, Min
Format: Article
Language:English
Subjects:
Applied physics
Crystals
Depth of field
Image resolution
Laser beams
Lithium niobates
Second harmonic generation
Wave diffraction
Wave fronts
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Summary:We experimentally demonstrate the use of a periodically poled LiNbO3 (PPLN) crystal to produce an ultra-long sub-diffraction optical needle via second-harmonic generation. When we input a radially polarized fundamental wave from a femtosecond laser, a sub-diffraction beam size of 0.45λSH and an ultra-long depth of focus (DOF) of 55λSH are experimentally realized, where λSH is the second harmonic wavelength. The lateral size of the second harmonic optical needle is reduced by a factor of 2 compared to the case using the fundamental wave. The compact experimental configuration can realize wavelength conversion and wave-front shaping simultaneously in a single PPLN crystal. In addition, the ultra-long DOF is potentially useful in observing thick samples. The unique characteristics of our second harmonic optical needle open the door for practical applications in super-resolution imaging and optical manipulation.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.5142522